JP3990128B2 - Magnetic recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording apparatus.
[0002]
[Prior art]
As the processing speed of computers in recent years increases, magnetic storage devices (HDDs) that are responsible for information storage and playback continue to be required to have higher speed and higher density. However, it is said that there is a physical limit to increasing the density, and there is a question as to whether or not this requirement can continue to be satisfied.
[0003]
A magnetic recording medium in which information is substantially recorded in the HDD includes a magnetic layer made of an aggregate of fine magnetic particles as a recording layer. In order to perform high-density recording on this magnetic recording medium, it is necessary to make the magnetic domain recorded on the magnetic layer as small as possible.
[0004]
Further, in order to be able to separate small magnetic domains, it is necessary that the boundaries of the magnetic domains be smooth, and for this purpose, it is necessary to make the magnetic particles as small as possible. Further, if the magnetization reversal is linked between adjacent magnetic particles, the boundary of the magnetic domain is disturbed. Therefore, it is necessary to magnetically separate the magnetic particles with a non-magnetic material so that the exchange coupling interaction does not work.
[0005]
In addition, in the HDD, the magnetic head needs to increase the interaction with the magnetic layer of the magnetic recording medium in order to read the magnetic information recorded on the magnetic recording medium. For this purpose, it is necessary to reduce the thickness of the magnetic layer of the magnetic recording medium.
[0006]
In view of the above requirements, the volume of the magnetic reversal laminated structure (substantially equal to the magnetic particles) of the magnetic material constituting the magnetic layer of the magnetic recording medium must be made smaller and smaller.
[0007]
However, if the magnetization reversal layered structure is miniaturized, the magnetic anisotropy energy (magnetic anisotropy energy density K_uThe volume V) of the magnetization reversal unit becomes smaller than the thermal fluctuation energy, and the magnetic domain can no longer be retained. This is a thermal fluctuation phenomenon, and the physical limit of the recording density mainly caused by this thermal fluctuation phenomenon is called a thermal fluctuation limit.
[0008]
As one method for preventing the reversal of magnetization due to thermal fluctuation, it is conceivable to make the magnetic anisotropy energy of the magnetic layer larger than the thermal fluctuation energy. However, when the magnetic anisotropy energy of the magnetic layer is increased, the coercive force when forming (recording) the reversal magnetic domain in the magnetic layer is substantially proportional to the magnetic anisotropy energy, and thus becomes too large, at most 12 kOe. There arises a problem that recording cannot be performed with a magnetic field that can be generated by a current recording head formed of permalloy, Fe, or Fe alloy that generates a magnetic field of a certain degree.
[0009]
In order to enable recording with the current recording head even when the magnetic anisotropy energy of the magnetic layer, which is the above problem, is increased, heat-assisted magnetic recording has been proposed.
[0010]
In heat-assisted magnetic recording, recording is performed by locally heating a magnetic layer during recording to reduce the magnetic anisotropy energy of a recording region. Thermally assisted recording allows recording with the current head by locally heating only the recording area and reducing the magnetic anisotropy energy in this area even if the magnetic anisotropy energy of the magnetic layer at room temperature is large become.
[0011]
However, in the heat-assisted magnetic recording, the adjacent track portion is heated to some extent at the time of recording, and therefore, a phenomenon (cross erase) in which the recording magnetic domain is erased by accelerating the thermal fluctuation occurs.
[0012]
Further, since the magnetic layer is heated to some extent even when the magnetic field from the recording head disappears immediately after recording, similarly, there is a problem that the magnetic domain once formed disappears due to accelerated thermal fluctuation.
[0013]
To solve these problems, magnetic anisotropy energy density K_uIt is necessary to use a material whose change with respect to the temperature is as steep as possible near the recording temperature. That is, during recording, the magnetic anisotropy energy density K suddenly increases as the temperature rises._uDecreases to a recordable value, and after recording, the magnetic anisotropy energy density K suddenly increases as heat diffuses._uNeeds to rise to prevent thermal fluctuations.
[0014]
However, magnetic anisotropy energy density K of CoCr-based magnetic thin film or CoPt-based magnetic thin film, which is currently being developed as a material having high coercive force._uThe change in temperature of the film is almost linear, so the magnetic anisotropy energy density K with respect to the heat diffusion rate_uDoes not return to its original value so quickly. Therefore, the current thermally assisted magnetic recording cannot solve the problem of loss of recording magnetization or cross erase after recording.
[0015]
[Problems to be solved by the invention]
As described above, in the conventional heat-assisted magnetic recording, the magnetic anisotropy energy density K of the magnetic material used for the magnetic recording medium._uMagnetic anisotropy energy density K immediately after recording due to slow temperature change of_uHowever, there is a problem that recording magnetization disappears or cross erase occurs due to thermal fluctuations.
[0016]
The present invention has been made in view of the above problems, and provides a magnetic recording apparatus that does not cause the disappearance of recording magnetization immediately after recording or the cross erase phenomenon that occurs due to acceleration of thermal fluctuations when performing thermally assisted magnetic recording. The purpose is to do.
[0017]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides a nonmagnetic substrate and a Curie temperature Tc formed on the nonmagnetic substrate.^FLAnd magnetic anisotropy energy density Ku^FLA functional layer made of a magnetic material having a Curie temperature laminated on the functional layer so as to exert an antiferromagnetic exchange coupling interaction with the functional layer.Tc ^FL thanHigh Curie temperature Tc^RLAnd 5 × 10⁶magnetic anisotropy energy density Ku above erg / cc^RLA recording layer comprising a magnetic particle having a non-magnetic material formed between the magnetic particles, the functional layer and the recording layer,Higher than room temperature, Tc ^FL Recording temperature Tw below the vicinityThere is provided a magnetic recording apparatus comprising heating means for heating the recording layer and magnetic recording means for recording signal magnetization by applying a magnetic field to the recording layer.
[0018]
At this time, the magnetic anisotropy energy density K_u ^FLIs the magnetic anisotropic energy density K_u ^RLThe following is preferable.
[0019]
The magnetic anisotropy energy density K_u ^FL> The magnetic anisotropy energy density K_u ^RLIt is preferable that it is x0.1.
[0020]
The magnetic anisotropic energy density K at the recording temperature Tw_u ^RLIs the anisotropic energy density K at room temperature_u ^RLIt is preferable that it is larger than 1/4.
[0021]
The Curie temperature T_c ^FLMagnetic anisotropy energy density K in_u ^RLIs magnetic anisotropy energy density K at room temperature_u ^RLIt is preferable that it is larger than 1/4.
[0022]
Moreover, it is preferable to have a nonmagnetic intermediate layer having a thickness of 5 nm or less between the recording layer and the functional layer.
[0023]
The nonmagnetic intermediate layer is a semiconductor doped with at least Ru, Re, Rh, Ir, Tc, Au, Ag, Cu, Si, Fe, Ni, Pt, Pd, Cr, Mn, Al, a semiconductor, and a magnetic substance. It is preferable that it consists of material chosen from these.
[0024]
  The present invention also provides a nonmagnetic substrate,
  Formed on the non-magnetic substrate, the amount of magnetization at room temperature is greater than the amount of magnetization at the recording temperature Tw.smallA functional layer made of a ferrimagnetic material;
  A recording layer comprising magnetic particles laminated on the functional layer so as to exert a ferromagnetic exchange coupling interaction with the functional layer, and a non-magnetic material formed between the magnetic particles;
  Heating means for heating the functional layer and the recording layer to the recording temperature Tw;
  There is provided a magnetic recording apparatus comprising magnetic recording means for recording signal magnetization by applying a magnetic field to the recording layer.
[0025]
At this time, the functional layer is preferably made of a rare earth and a transition metal alloy.
[0026]
In addition, the functional layer includes a first magnetic layer and a second magnetic layer that is antiferromagnetic exchange coupled with the first magnetic layer, and a multilayer structure is laminated a plurality of times, and the first magnetic layer and The Curie temperature is preferably different from that of the second magnetic layer.
[0027]
Moreover, it is preferable that a laminated structure including the functional layer and the recording layer is laminated a plurality of times.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0029]
(Embodiment 1)
FIG. 1 shows an outline of a magnetic disk apparatus using a rotary actuator.
[0030]
As shown in FIG. 1, a disk 101, which is a magnetic storage medium, is mounted on a spindle 110 and rotated at a predetermined rotational speed. There is provided a recording head 1 equipped with a magnetic recording / reproducing element and a heating means for recording / reproducing information while floating on or in contact with the disk 101. The recording head 1 is attached to the tip of a thin plate suspension 50. Here, as the magnetic recording generating element, an element made of permalloy, Fe or Fe alloy can be used. A magnetic field of about 5 kOe to 6 kOe is sufficient.
[0031]
The suspension 50 is connected to one end of an actuator arm 102 having a bobbin portion for holding a drive coil (not shown). On the other hand, the other end of the actuator arm 102 is provided with a voice coil motor 120 which is a kind of linear motor.
[0032]
The voice coil motor 120 includes a drive coil (not shown) wound around a bobbin portion of the actuator arm 102, and a magnetic circuit including a permanent magnet and a counter yoke that are arranged to face each other with the coil interposed therebetween.
[0033]
The actuator arm 102 is held by a ball bearing (not shown) provided on the fixed shaft 130 and can be freely rotated and swung by the voice coil motor 120. These configurations are arranged in the housing 100.
[0034]
FIG. 2 is a cross-sectional view of the recording head 1 and the disk 101 which is a magnetic recording medium shown in FIG.
[0035]
As shown in FIG. 2, a disk 101 as a magnetic recording medium is formed on a nonmagnetic substrate 13, a functional layer 12 formed thereon, a recording layer 11 formed thereon, and a recording layer 11 formed thereon. And a protective layer 14.
[0036]
As the nonmagnetic substrate 13, a circular hard substrate can be used. The material of the substrate 13 can be a non-magnetic material such as metal, glass, or ceramics.
[0037]
The recording layer 11 includes magnetic particles and a nonmagnetic material formed therebetween. As a material for magnetic particles present in the recording layer 11, a material having a large saturation magnetization Is and a large magnetic anisotropy is suitable. From this viewpoint, it is preferable to use at least one selected from the group consisting of Co, Pt, Sm, Fe, Ni, Cr, Mn, Bi, Al, and alloys of these metals as the magnetic metal material of the magnetic particles.
[0038]
Among these, Co-based alloys having a large magnetocrystalline anisotropy, particularly those based on CoPt, SmCo, and CoCr, and ordered alloys such as FePt and CoPt are more preferable. Specifically, CoCr, CoPt, CoCrTa, CoCrPt, CoCrTaPt, Fe₆₀Pt₆₀, Fe₆₀Pd₆₀, Co₃Pt₁Etc. In addition to these, alloys of rare earths and transition metals such as TbFe, TbFeCo, TbCo, GdTbFeCo, GdDyFeCo, NdFeCo, NdTbFeCo, and the like can be given.
[0039]
Examples of the recording layer 11 include a multilayer film (Co / Pt, Co / Pd, etc.) of a magnetic layer and a noble metal layer. The recording layer 11 may be a semimetal such as PtMnSb. The recording layer 11 can be selected from a wide variety of magnetic oxides such as Co ferrite and Ba ferrite.
[0040]
For the purpose of controlling the magnetic properties of the magnetic fine particles contained in the recording layer 11, the magnetic material may be further alloyed with at least one element selected from Fe and Ni. In addition to these metals or alloys, additives for improving magnetic properties, such as elements such as Cr, Nb, V, Ta, Ti, W, Hf, Cr, In, Si or B, or these elements and oxygen A compound with at least one element selected from nitrogen, carbon, and hydrogen may be added.
[0041]
The magnetic anisotropy of the recording layer 11 may be perpendicular magnetic anisotropy, in-plane magnetic anisotropy, or a mixture thereof.
[0042]
The thickness of the recording layer 11 is not particularly limited, but is preferably 100 nm or less, more preferably 50 nm or less, and still more preferably 20 nm or less in order to realize high-density recording. If it is 0.5 nm or less, it is difficult to form a thin film, which is not preferable.
[0043]
Nonmagnetic elements such as Cr, Ta, and B, or SiO can be used as a method of forming a nonmagnetic material between magnetic particles contained in the recording layer 11 and dividing it.₂Oxide represented by Si,₂N₃There is a method in which a non-magnetic material such as a nitride is used to precipitate between grains.
[0044]
In addition, a nonmagnetic material may be formed between the magnetic particles by artificial processing using a technique such as lithography used in semiconductors. Further, a non-magnetic material may be formed between the magnetic particles by self-assembly processing using a diblock copolymer such as PS-PMMA that is self-organized as a mask. Further, a non-magnetic material may be formed between magnetic particles by processing such as particle beam irradiation.
[0045]
The functional layer 12 may be anything as long as it is a magnetic material. The magnetic anisotropy may be perpendicular magnetic anisotropy, in-plane magnetic anisotropy, or a mixture thereof.
[0046]
The thickness of the functional layer 12 is not particularly limited. However, the thickness of 1000 nm or more is not preferable because it takes a long time to produce, and characteristic deterioration or peeling is likely to occur due to film stress. A thickness of 0.1 nm or less is not preferable because a thin film cannot be substantially formed. The requirements to be satisfied by the functional layer as a magnetic material are the same as those of the recording layer.
[0047]
In the exchange coupling interaction between the functional layer 12 and the recording layer 11, the functional layer 12 is formed in a general medium manufacturing process such as sputtering, and the recording layer 11 is subsequently formed without breaking the vacuum. This can be achieved. However, at this time, when the spin directions of the functional layer 12 and the recording layer 11 are antiparallel, it is necessary to make the energy lowest. This is an antiferromagnetic exchange coupling interaction.
[0048]
A configuration that develops an antiferromagnetic exchange coupling interaction can be realized by controlling the state of the interface between the recording layer 11 and the functional layer 12. For example, there are examples in which a region having partially changed magnetism, a surface modified layer or a physical / chemical adsorption layer is formed, and an interface bonding state varies depending on a micro part.
[0049]
In any case, even if the gap between the recording layer 11 and the functional layer 12 is theoretically separated by several nanometers, the antiferromagnetic exchange coupling interaction is exerted. There may be a nonmagnetic layer between the layer 12 and the recording layer 11.
[0050]
In addition, since the antiferromagnetic exchange coupling force can be controlled by inserting another magnetic film between the functional layer 12 and the recording layer 11, a plurality of layers between the functional layer and the recording layer can be used as long as the effects of the present invention are not impaired. The magnetic layer may be present.
[0051]
In addition, the laminated structure of the functional layer 12 and the recording layer 11 can provide the effect of the magnetic recording medium of the present invention, but a protective layer 14 may be formed on the recording layer 11 as necessary. As the protective layer 14, C or SiO₂The thin film which consists of etc. can be used.
[0052]
In addition, a base layer can be used between the substrate 13 and the functional layer 12. By using the underlayer, the controllability of various characteristics of the functional layer 12 and the recording layer 11 can be improved. The underlayer may be a magnetic material or a non-magnetic material. The thickness of the underlayer is not particularly limited, but if it is thicker than 500 nm, the production cost increases, which is not preferable.
[0053]
By using the underlayer as a magnetic material and magnetically coupling with the magnetic domain in the magnetic material of the recording layer 11 and the recording head 1 via exchange interaction or magnetostatic interaction, efficient recording and reproduction on the magnetic thin film is achieved. It can be carried out. For example, when the recording layer 11 is a perpendicular magnetization film, high-density recording can be performed by using a soft magnetic film as an underlayer and recording with a single pole head. In this case, recording can be performed on the recording medium 101 even if the magnetic field of the recording head is smaller.
[0054]
Further, when the recording layer 11 is an in-plane magnetization film, high-density recording can be performed by providing a soft magnetic layer above or below the recording layer 11 and applying a magnetic field that saturates the soft magnetic layer during reproduction. Also, the resistance to thermal fluctuation is improved.
[0055]
Moreover, the crystal structure of a magnetic part or a nonmagnetic part is controllable by making a base layer into a nonmagnetic material. Further, it is possible to prevent impurities from the substrate 13 from entering the functional layer 12 and the recording layer 11. At this time, a thin film having a small lattice spacing or a dense layer may be used as the base layer.
[0056]
In addition, the crystal state of the magnetic part can be controlled by using an underlayer having a lattice spacing close to the lattice spacing of the crystal orientation of the magnetic part.
[0057]
In some cases, for example, the crystallinity or amorphousness of the magnetic part or the nonmagnetic part is controlled by using an amorphous base having a certain surface energy.
[0058]
Further, a base layer may be further provided under the base layer. In that case, since the function is shared, the effect is increased. For example, a seed layer having a small particle diameter can be provided on the substrate 13 for the purpose of reducing the crystal grains of the recording layer 11, and an underlayer for controlling the crystallinity of the recording layer 11 can be provided thereon.
[0059]
The magnetic and non-magnetic underlayers may have a common function. In other words, there may be a magnetic underlayer for controlling the crystallinity of the magnetic part. In this case, since the effect on the recording or reproduction characteristics and the effect on the crystallinity are synergistic, it is preferable to each case.
[0060]
The underlayer may be a surface modified layer of the substrate 13 that is formed by ion plating, doping in an atmospheric gas, neutron beam irradiation, or the like. In this case, it is not necessary to go through a process of depositing a thin film, which is preferable in producing a magnetic recording medium.
[0061]
The recording head 1 can be heated locally while applying a local magnetic field directly below the recording head 1. By applying a local magnetic field, a fine magnetization reversal portion can be created in the recording layer 11.
[0062]
The heating means may be either one that heats the entire surface of the disk 101, which is a magnetic recording medium, or one that heats only the local portion, as long as the portion reaching the recording temperature is local. In general, considering the record retention characteristics (archive characteristics) and power consumption, it is preferable to heat locally and keep most of the medium at or below room temperature.
[0063]
In order to perform local heating at high speed, a laser used for an optical disk, an induction heating, a probe heated by a heating wire, or the like, or an electron beam is used. Something to be released is considered.
[0064]
In addition, in order to perform more local heating, a system in which laser light is squeezed on the surface of a medium using a lens or the like, or a system in which laser light is used as a near-field light using a minute aperture or a solid immersion lens. Alternatively, a method of making a fine antenna at the tip of the probe and performing induction heating therefrom, a method of sharpening the shape of the medium facing portion of the heating probe as much as possible, or shortening the approaching distance, or a medium facing of the electron beam emission probe A method of sharpening the shape of the part as much as possible is mentioned. The heating device using these methods may be on the recording surface side of the medium or on the opposite surface side.
[0065]
As a means for applying a magnetic field existing in the recording head 1, one having a magnetic circuit composed of an induction coil and a magnetic pole on the end face of a flying slider as used in a normal HDD can be used. Further, a permanent magnet may be installed, or a magnetic layer may be further added to the magnetic recording medium, and an instantaneous and local magnetic field may be generated by a temperature distribution or a magnetization distribution by light irradiation. Further, a leakage magnetic field generated from the magnetic layer itself for recording information may be used.
[0066]
When a permanent magnet is used as a recording head, recording can be performed if the distance between the permanent magnet and the medium is made variable and the magnet is moved closer, and recording is not performed if the distance is increased. When overwriting what has been recorded once, the magnet may be reversed and the same may be done. Further, high-density recording is possible by miniaturizing the magnet. Further, the speed can be increased by moving the piezoelectric element at high speed.
[0067]
In the present invention, the stored magnetic recording information can be read using the same method as that of a conventional magnetic recording apparatus. That is, the leakage magnetic field from the magnetic recording medium 101 is detected by the magnetic reproducing head 1 using the giant magnetoresistance effect. In other words, since the recorded information can be read without irradiating light, compatibility with a conventional reading system is ensured.
[0068]
The Curie temperature Tc of the magnetic material of the recording layer 11 and the functional layer 12 can be examined by the temperature dependence of the magnetization M or the coercive force Hc. When measuring magnetic properties by VSM or the like, it is necessary to keep the heating state for about 10 minutes, and since the rate of temperature rise cannot be shortened, the sample is held at that temperature for about one hour.
[0069]
In the case of a magnetic thin film, there is a possibility that an irreversible fine structure change occurs due to this high temperature holding for a long time, and accurate magnetic property evaluation cannot be performed. In the case of amorphous rare earths and transition metal alloys used as magneto-optical recording media, such changes are relatively unlikely, but CoCrPt-based media used as HDD media have a change in microstructure of 200. It may occur at about ℃.
[0070]
Even in such a case, the Curie temperature Tc can be estimated. That is, a change in magnetic properties from room temperature or lower to a temperature at which structural change occurs may be extrapolated to the high temperature side.
[0071]
The request for the Curie temperature Tc in the magnetic recording apparatus according to the present invention is substantially the magnetic anisotropy energy density K._uIt is sufficient if the temperature is such that the value of the magnetization M and the coercive force Hc can be estimated to be about 1/20 of the value at room temperature.
[0072]
Further, the magnetic anisotropy energy density K of the recording layer 11_u ^RLIs 5 × 10⁶erg / cc or higher. This is because if it is smaller than this, the merit of the heat-assisted magnetic recording cannot be obtained.
[0073]
FIG. 3 shows the magnetic anisotropy energy density K of the recording layer 11._u ^RL, Magnetic anisotropy energy density K of functional layer 12_u ^FL, Reversal magnetic field H of the entire magnetic recording medium_c ^totalThe recording magnetic field H applied from the recording head 1_wThe change with respect to temperature is typically shown.
[0074]
As shown in FIG. 3, the Curie temperature T of the functional layer 12_c ^FLIs the Curie temperature T of the recording layer 11_c ^RLLower than. Further, the magnetic anisotropic energy density K of the functional layer 12_u ^FLIs the magnetic anisotropy energy density K of the recording layer 11_u ^RLAnd changes more rapidly with temperature change.
[0075]
The functional layer 12 and the recording layer 11 are antiferromagnetic exchange coupled. Therefore, a reversal magnetic field H that reverses the synthesized magnetization._c ^totalIs the Curie temperature T of the functional layer 12_c ^FLIn the following temperature range, the magnetic anisotropy density K of the recording layer 11 is_u ^RLIt has a sufficiently large value that changes rapidly with respect to temperature change. In this temperature range, there is no problem of inversion due to the thermal fluctuation phenomenon.
[0076]
Curie temperature T of functional layer 12_c ^FLWhen the medium temperature rises more than the magnetic anisotropy density K of the functional layer 12_u ^FLBecomes 0, and the magnetic anisotropy density K of the recording layer 11_u ^RLReversal magnetic field H only by_c ^totalIs determined. Therefore, the recording temperature Tw is set to the Curie temperature T of the functional layer 12._c ^FLBy making it larger than this, it can be reversed by the recording magnetic field Hw of the recording head 1.
[0077]
By doing so, it is possible to solve the problem of lost recording magnetization and cross erase immediately after recording without making the temperature change of the magnetic anisotropy energy density Ku steep even if thermal diffusion is slow.
[0078]
The heat-assisted magnetic recording using this characteristic will be described in detail.
[0079]
FIG. 4 is a cross-sectional structure of the magnetic recording medium, and schematically shows the state of magnetization reversal in the recording layer 11 and the functional layer 12. Reference numeral 31 denotes a magnetic particle, and an arrow therein indicates the direction of magnetization. The length of the arrow represents the magnitude of the magnetization or reversal field. Reference numeral 32 denotes a nonmagnetic material between the magnetic particles 31. The functional layer 12 also has a structure made up of magnetic particles similar to the recording layer 11 and a nonmagnetic material that divides them. In addition to this structure, for example, a continuous film or a (three-dimensional) granular structure may be used. Here, for the sake of simplicity, a case of a perpendicular magnetic recording medium will be described as an example. However, the description here can be applied to an in-plane medium or a mixture of both as it is.
[0080]
Since the functional layer 12 is antiferromagnetic exchange coupled with the recording layer 11, its magnetization is opposite to the magnetization of the recording layer 11. For this reason, the total amount of magnetization of the recording medium is smaller than the amount of magnetization in the case of the recording layer 11 alone, and therefore the reversal field is increased. Magnetic anisotropy energy density K_uIn contrast, the reversed magnetic field, that is, the anisotropic magnetic field H_kIs H_k= 2K_u/ Ms. Ms is saturation magnetization.
[0081]
First, as shown in FIG. 4A, all the magnetizations of the recording layer 11 are set downward as an initial state. This state is a state of room temperature Ta before heat application and magnetic field application. Due to the antiferromagnetic exchange coupling interaction with the recording layer 11, the functional layer 12 exhibits upward magnetization and is antiferromagnetic exchange coupled with the magnetization of the recording layer 11, and its coercive force is large.
[0082]
Since heating is not performed in this state, there is no loss of magnetization due to thermal fluctuation. This state is a state of room temperature Ta in FIG. The reversal magnetic field H at this time_c ^totalIs the magnetic anisotropy energy density K of the functional layer 12_u ^FLAnd magnetic anisotropy energy density K of recording layer 11_u ^RLIt is proportional to the value when and are combined.
[0083]
Next, as shown in FIG. 4B, only the range indicated by the arrow 34 is heated by the heat application means built in the recording head (reference numeral 1 in FIG. 2). As shown in FIG. 3, as the substrate temperature rises from room temperature Ta to recording temperature Tw by applying heat, the reversal magnetic field H suddenly increases._c ^totalDecreases. This is the Curie temperature T of the functional layer 12_c ^FLIs lower than the recording layer 12 and magnetic anisotropy energy density K_u ^FLThis is because of a sudden drop. Thus, the state immediately before the recording is performed.
[0084]
Next, as shown in FIG. 4C, a downward magnetic field is applied from the recording head (reference numeral 1 in FIG. 2) to form a recording magnetic domain having a downward spin. The spin relationship between the recording layer 11 and the functional layer 12 is inverted and reversed in the opposite direction. As shown in FIG. 3, at the recording temperature Tw, the reversal magnetic field H_c ^totalIs the recording magnetic field H of the recording head 1_wTherefore, the spin can be easily reversed. Here, the recording temperature Tw is the Curie temperature T of the functional layer 12._c ^FLIt may be higher and the magnetization of the functional layer 12 may disappear.
[0085]
Next, as shown in FIG. 4D, after the downward spin recording magnetic domain is formed, the heat application is stopped. Thus, when the temperature returns to room temperature Ta as shown in FIG. 3, the magnetization of the functional layer 12 suddenly increases. As a result, the switching magnetic field H_c ^totalSuddenly grows.
[0086]
As described above, according to the present invention, magnetic recording can be performed on a recording layer having a large magnetic anisotropy energy density Ku that cannot be recorded at room temperature.
[0087]
Further, according to the present invention, in order to bring about a situation where recording can be performed by a change in the magnetic characteristics of the functional layer having a low Curie temperature, the magnetism of the recording layer itself does not change so much from room temperature to the recording temperature. Thermal fluctuation acceleration, which is a problem of conventional heat-assisted magnetic recording, is less likely to occur.
[0088]
In the present invention, the magnetic anisotropy energy density K of the recording layer 11_u ^RLAnd magnetic anisotropy energy density K of functional layer 12_u ^FLThe magnitude relationship at room temperature is basically arbitrary. However, in order to realize a higher-density magnetic recording apparatus, the magnetic anisotropy energy K of the functional layer 12 at room temperature._u ^FLIs the magnetic anisotropy energy density K of the recording layer 11_u ^RLThe following should be better. Further, the recording layer 11 and the functional layer 12 may have the same magnetic anisotropic energy density.
[0089]
In the present invention, the magnetic anisotropic energy density K of the functional layer 12 is_u ^FL> Magnetic anisotropy energy density K of recording layer 11_u ^RLA relationship of × 0.1 is preferable. As described above, the magnetic anisotropy energy density K of the functional layer 12_u ^FLIs the magnetic anisotropy energy density K of the recording layer 11_u ^RLThe following should be better. However, the magnetic anisotropic energy density K of the functional layer 12_u ^FLIt doesn't mean it can be as small as possible.
[0090]
The inventors have determined that the effective magnetic anisotropy energy density K of the multilayer film formed by ferromagnetic exchange coupling and antiferromagnetic exchange coupling._uAs a result of investigating what kind of characteristics it shows, the following findings were found.
[0091]
That is, when the first layer and the second layer are bonded with an exchange coupling energy surface density σ, the magnetic anisotropy energy density as the overall thermal fluctuation resistance is
σ / (2t₂K_u2) <1, t₁K_u1+ Σ-σ²/ (4t₂K_u2)
σ / (2t₂K_u2)> 1, t₁K_u1+ T₂K_u2
It becomes.
[0092]
Where t₁, T₂Are the film thicknesses of the first and second layers, respectively, K_u1, K_u2Are the magnetic anisotropy energy densities of the first layer and the second layer, respectively.
[0093]
In all cases, heat fluctuation resistance tK as a whole_uIs increasing. However, the average for the entire membrane is (t₁+ T₂), As you can see,_u2Only K_u1Therefore, the effective magnetic anisotropy energy density is reduced.
[0094]
In order to increase the density, the medium must be thinned._u1This is a disadvantage compared to the case where the same material is used.
[0095]
Therefore, the magnetic anisotropy energy density K of the functional layer 12_u ^FLIs the magnetic anisotropy energy density K of the recording layer 11_u ^RLIs preferably as large as possible within a smaller range. As a result of detailed experiments and examinations, specifically, the magnetic anisotropy energy density K of the functional layer 12_u ^FL> Magnetic anisotropy energy density K of recording layer 11_u ^RLIt was found that the relationship of × 0.1 is sufficient.
[0096]
In the present invention, the magnetic anisotropy energy density K of the recording layer 11 at the recording temperature Tw is used._u ^RLIs the magnetic anisotropy energy density K of the recording layer 11 at room temperature._u ^RLIt should just be larger than 1/4 of.
[0097]
The greatest feature of the magnetic recording apparatus according to the present invention is to suppress the thermal fluctuation acceleration phenomenon. Specifically, recording is performed before the thermal fluctuation of the recording layer 11 is accelerated by utilizing the change of the entire reversal magnetic field due to the change of the magnetic characteristics of the functional layer 12. That is, recording is performed at a temperature sufficiently lower than the Curie temperature of the recording layer 11.
[0098]
As a result of the inventors' independent research, when performing thermally assisted magnetic recording on a normal single layer film, the thermal fluctuation acceleration phenomenon can be avoided at a temperature at which the magnetic anisotropy energy density at room temperature is approximately halved. I got the knowledge that However, this conclusion contains assumptions for simplicity and has been found to give an overestimation of thermal fluctuation acceleration. Actually, a complicated phenomenon involving the change in temperature in the nanometer region on the medium and the spatial distribution of the magnetic properties associated therewith has occurred, so accurate analysis cannot be performed unless first-principles simulation is used. As a result of conducting detailed experiments in consideration of these points, the inventors have found that the magnetic anisotropy energy density K of the recording layer 11 at room temperature._u ^RLIt has been found that the effect of the thermal fluctuation acceleration phenomenon can be suppressed by measures such as improving the temperature response if heating is performed until the value of the magnetic anisotropy energy density becomes ¼ of the value.
[0099]
That is, the magnetic anisotropic energy density K of the recording layer 11 at the recording temperature Tw._u ^RLIs larger than 1/4 of the value at room temperature, heat-assisted magnetic recording with suppressed thermal fluctuation can be performed. At this time, there is no deterioration immediately after recording, and no cross erase occurs because thermal fluctuation acceleration does not occur in adjacent tracks. In addition, since the reversal magnetic field in a region wider than the magnetic field application region of the recording head (generally, the region of the ABS surface of the recording magnetic pole) can be made equal to or less than the recording magnetic field, the recorded magnetic domain is rectangular that is not affected by the isotherm It also has the advantage of being able to.
[0100]
This condition is only for suppressing thermal fluctuation acceleration, such as a system that allows a certain degree of deterioration, a system that employs application of an auxiliary magnetic field immediately after recording, a system that has an extremely fast temperature response due to an extremely rapid refrigerant structure, etc. It is not necessary to use for.
[0101]
In order to enable recording at a lower temperature, the recording layer 11 itself has a high magnetic anisotropy energy density K._u ^RLIt is preferable that the material has a low coercive force. To do so, the saturation magnetization Ms of the recording layer 11 is preferably large. However, basically the magnetic anisotropy energy density K_u ^RLThe saturation magnetization Ms is a value inherent to the material and cannot be controlled so much.
[0102]
Therefore, another layer can be realized by ferromagnetic exchange coupling with the recording layer 11. That is, the second recording layer made of another material having a high magnetic anisotropy energy density is exchange-coupled to the recording layer 11 to saturate when the recording layer 11 and the second recording layer are regarded as one body. Magnetization Ms can be increased, resulting in high magnetic anisotropy energy density K_u ^RLIn addition, a low coercive force can be realized. In this case, the magnetic anisotropy energy density of the second recording layer is equal to the magnetic anisotropy energy density K of the recording layer 11._u ^RLIt doesn't have to be as expensive.
[0103]
As such a material system, for example, in the case of a perpendicular magnetic recording medium, a so-called artificial lattice medium in which Co layers having a thickness of about 1 nm and Pt layers and Pd layers are alternately stacked can be used. In this medium, since the magnetic anisotropy energy density can be increased as the Co layer is thinner, for example, the Co layer is 0.25 nm thick and the Pt layer is 0.5 nm.⁷Ms of about 500 emu / cc can be obtained at a magnetic anisotropy energy density of erg / cc.
[0104]
In the present invention, the Curie temperature T of the functional layer 11 is_c ^FLMagnetic anisotropy energy density K of the recording layer 11 at_u ^RLIs the magnetic anisotropic energy density K of the recording layer 11 at room temperature._u ^RLIt is preferable that it is larger than 1/4.
[0105]
The temperature change (decrease) of the coercive force Hc larger than the recording layer 11 originally has can be obtained in the temperature range in which the functional layer 12 has magnetism. That is, the largest decrease in coercive force Hc from room temperature (relative increase in saturation magnetization Ms) is obtained because of the Curie temperature T of the functional layer 11._c ^FLAt the following temperatures.
[0106]
  The magnitude of the coercive force at room temperature means that there is little magnetization at room temperature, which means that the effect of reducing the demagnetizing field is great. Therefore, the recording operation is performed using the Curie temperature Tc of the functional layer 12.^FLWhen performed in the vicinity, the demagnetizing field reduction effect can be increased, which is preferable. From the above discussion, in order to suppress the thermal fluctuation acceleration phenomenon, the recording temperature is changed to the magnetic anisotropic energy density Ku of the recording layer 11.^RLIs a quarter of the room temperature value, so to obtain a system that has both effects,Functional layer12 Curie temperature Tc^FLMagnetic anisotropy energy density Ku of the recording layer 11 at^RLIs the magnetic anisotropy energy density Ku of the recording layer 11 at room temperature.^RLIt is preferable that it is larger than 1/4.
[0107]
This condition is only for suppressing thermal fluctuation acceleration and reducing the influence of the demagnetizing field, and need not be used for a system or the like that does not require it. Whether this condition is adopted depends on the design of the system used.
[0108]
In the magnetic recording apparatus according to the present invention, a nonmagnetic intermediate layer of 5 nm or less may be formed between the recording layer 11 and the functional layer 12.
[0109]
Further, in the present invention, the antiferromagnetic exchange coupling can be realized by controlling the interface between the recording layer 11 and the functional layer 12, but as another method, a non-magnetic layer of 5 nm or less between the recording layer 11 and the functional layer 12 is used. It has been clarified by experiments by the inventors that this can be realized by forming an intermediate layer. It has been found that the exchange coupling between the recording layer 11 and the functional layer 12 acts at a distance not exceeding 5 nm, and the exchange coupling force can be controlled by the distance. This distance varies depending on the material used, the magnetic / mechanical / chemical state of the interface, the film formation method, the film formation conditions, etc., and cannot be uniquely defined here.
[0110]
In the present invention, in order to keep the distance between the recording layer 11 and the functional layer 12 with good control, an intermediate layer made of a nonmagnetic material may be inserted between them.
[0111]
In addition, the inventors have determined that the nonmagnetic intermediate layer is made of at least a material selected from Ru, Re, Rh, Ir, Tc, Au, Ag, Cu, Si, Fe, Ni, Pt, Pd, Cr, Mn, and Al. It has been found that a large exchange coupling energy can be obtained.
[0112]
In the case of the magnetic recording apparatus according to the present invention, the necessary conditions are that the thermal fluctuation acceleration is small at the recording temperature and the reversal magnetic field is small. There are various conditions for realizing this, and one of them is that the exchange coupling energy is large. This has an advantage that a recording layer having a larger magnetic anisotropy energy density that can increase the magnetic anisotropy energy density of the functional layer 12 can be used. However, a large exchange coupling energy is not an essential condition, and can be controlled by other parameters, or may be small depending on the system. In that case, the range of selection of the intermediate layer material is preferably increased.
[0113]
In addition, the inventors have found that the above-described nonmagnetic intermediate layer is selected from a semiconductor and a material doped with a magnetic substance in the semiconductor, so that a large exchange coupling energy and a sharp temperature change of a reversal magnetic field can be obtained. I found it. The reason why large exchange coupling energy is obtained is not well understood. Regarding the temperature change of the steep reversal magnetic field, when the intermediate layer is a semiconductor, the number of electrons (carriers) is considered to be responsible for the exchange coupling interaction between the recording layer 11 and the functional layer 12, but the number depends on the temperature. This is probably because the decrease in exchange coupling energy with respect to temperature was reduced by the increase. When a magnetic substance is doped in a semiconductor, the effect of increasing the exchange coupling energy is further obtained. Of course, it is not always necessary to use these semiconductor intermediate layers for a system in which the influence of the demagnetizing field is small in the first place.
[0114]
Next, an example in which a magnetic recording device having a cross-sectional structure schematically shown in FIG.
[0115]
First, a Ti seed layer (not shown) is formed with a thickness of 10 nm and a Pt underlayer (not shown) is formed with a thickness of 20 nm on a 2.5-inch glass substrate 13 by sputtering. Next, a functional layer 12 in which five layers of a laminated structure including a Co layer having a thickness of 0.32 nm and a Pt layer having a thickness of 0.78 nm are formed is laminated thereon by a sputtering method.
[0116]
Next, a magnetic material (Co₈₀Pt₂₀) Ta₆And during this, SiO as a non-magnetic material₂The recording layer 11 having a thickness of 10 nm is formed by sputtering with a thickness of 10 nm. Next, a protective layer 14 made of C is laminated on the recording layer 12 by sputtering with a thickness of 3 nm, and then a lubricant is applied.
[0117]
The functional layer 12 is a so-called artificial lattice in which a multilayer structure including a Co layer having a thickness of 0.32 nm and a Pt layer having a thickness of 0.78 nm is repeated five times. Between the functional layer 12 and the recording layer 11, 0.5 Pa of Ar and N₂A sputter etching process of RF 100 W is performed in an atmosphere.
[0118]
Next, when the fine structure of the recording layer 11 was analyzed using a TEM, columnar magnetic crystal particles (diameter of about 9 nm) mainly made of CoPt were found to be amorphous SiOP.₂It was the structure divided by the nonmagnetic material which consists of. In this analysis, Ta could not be analyzed.
[0119]
Further, the magnetic characteristics of the recording layer 11 alone have a main axis of easy magnetization in the vertical direction, and the magnetic anisotropy energy density K is determined by VSM measurement and magnetic torque measurement._u ^RL= 8 × 10⁶estimated to be erg / cc. Also, its Curie temperature T_c ^RLWas estimated to be about 800K.
[0120]
Similarly, the magnetic properties of the functional layer 12 alone are the magnetic anisotropy energy density K_u ^FL= 3 × 10⁷erg / cc, Curie temperature T_c ^FL= 500K.
[0121]
FIG. 5 schematically shows a hysteresis loop in a state where the functional layer 12 and the recording layer 11 are laminated.
[0122]
As shown in FIG. 5, when the absolute value of the magnetic field strength is decreased from the saturation state on the negative side, H₂And H₁The sudden change in magnetization appeared twice. This means that the functional layer 12 and the recording layer 11 have an antiferromagnetic exchange coupling interaction.
[0123]
When the absolute value of the magnetic field strength is decreased from the minus side, first, H₂, The functional layer 12 is inverted, and the spin directions of the recording layer 11 and the functional layer 12 become antiparallel. Since this state is stable in terms of energy, it is maintained as it is even under a zero magnetic field.
[0124]
Next, when the magnetic field strength increases to the plus side, the magnetization of the recording layer 11 is forcibly reversed by the force of the external magnetic field. This is H₁Changes.
[0125]
This hysteresis loop measurement is performed by changing the temperature.₁As a result of examining the temperature change, the H shown schematically in FIG._c ^totalIt was found that it has the following characteristics. This characteristic is brought about by the antiferromagnetic exchange coupling interaction between the functional layer 12 and the recording layer 11.
[0126]
The dynamic characteristics of the magnetic recording medium were evaluated with a HDD recording / reproduction evaluation apparatus. The rotational speed was 4500 rpm, the recording gap was 200 nm, and the reproducing head using the GMR element had a gap of 110 nm. The magnetic spacing was estimated to be 30 nm from the flying height and the lubricant thickness. A laser with a wavelength of 633 nm was used for local heating. The laser was applied to the interface portion between the functional layer 12 and the recording layer 11 from the back surface of the substrate via an external low floating lens. The design was made so that both the external low-levitation lens and the substrate were SIL lenses, and the focal point was formed at the interface between the functional layer 12 and the recording layer 11. The diameter of the laser spot is about 500 nm in FWHM. By driving the head with a precise piezo element, the light irradiation position and the gap position of the recording head were matched.
[0127]
First, magnetic recording was attempted without laser irradiation. It was found that the reproduced signal was mostly noisy and sufficient recording was not possible. This is a natural result considering the coercive force of the recording layer 11 and the recording capability of the recording head.
[0128]
Next, recording was performed while irradiating a laser. By another experiment and simulation, the relationship between the laser irradiation power and the temperature rise of the magnetic recording medium is grasped in advance, and the relationship between the recording temperature Tw and the CN ratio (CNR) of the reproduction signal is changed by changing the irradiation laser power. Examined. As a result of performing 400 kfci single frequency recording, a reproduction signal can be obtained in a region where the recording temperature Tw = 350K or higher, the maximum signal intensity is obtained around the recording temperature Tw = 450K to 550K, and the recording temperature Tw = 800K. The signal could not be obtained again.
[0129]
Such dependence of the reproduction signal intensity on the medium temperature is appropriate in view of the action of the above-described heat-assisted magnetic recording system.
[0130]
Next, after forming the functional layer 12, instead of performing RF sputter etching, Ar and O of 1 Pa are used.₂A sample was prepared by exposing to the atmosphere for 1 minute and then forming the recording layer 11 and the protective layer 14 in the same manner as described above.
[0131]
As a result of cross-sectional TEM observation, it was found that a CoO layer having a thickness of 1 nm was formed between the functional layer 12 and the recording layer 11.
[0132]
When the hysteresis curve of this sample was measured, the same one as shown in FIG. 5 was obtained. Based on this result, an SiO layer having a thickness of 0.8 nm is formed as an intermediate layer between the functional layer 12 and the recording layer 11.₂A sample in which a layer, a Ti layer with a thickness of 1 nm, a Ti layer with a thickness of 3 nm, and a TiPt layer with a thickness of 5 nm were inserted was prepared.
[0133]
In any case, the same characteristics as in FIG. 6 were obtained, and it was found that antiferromagnetic coupling was obtained. In particular, when a 1 nm thick Ti layer is inserted as an intermediate layer, H₁And H₂It was estimated that the difference between and was the largest, and the exchange coupling energy was the largest. Exchange coupling was not obtained when the thickness of the intermediate layer exceeded 5 nm.
[0134]
Next, another example according to the first embodiment will be described.
[0135]
First, a NiAl seed layer (not shown) with a thickness of 5 nm and a V underlayer (not shown) with a thickness of 10 nm are formed on a 2.5-inch glass substrate 13 by sputtering. Next, on this (Co₁₆Pt₂₄) Cr₁-O functional layer 12 has a thickness of 10 nm, Ru intermediate layer (not shown) has a thickness of 0.8 nm, (Fe₆₃Pt₄₁) Cu₁₂-SiO₂The recording layer 11 was laminated with a thickness of 12 nm and the C protective layer 14 was laminated with a thickness of 3 nm sequentially by sputtering, and then a lubricant was applied.
[0136]
Next, when the fine structure of the recording layer 11 of the magnetic recording medium thus formed was examined using a TEM, columnar magnetic crystal particles (diameter about 5 nm) mainly made of FePt were found to be amorphous SiO.₂It was the structure divided by the nonmagnetic material which consists of. Cu was almost uniformly distributed in the film.
[0137]
The magnetic characteristic of the recording layer 11 alone has a main axis of easy magnetization in the in-plane direction, and the magnetic anisotropy energy density K is determined by VSM measurement and magnetic torque measurement._u ^RLIs 8 × 10⁷ estimated to be erg / cc. Curie temperature T of the recording layer 11_c ^RLWas estimated to be about 700K.
[0138]
The magnetic properties of the functional layer 12 alone are the magnetic anisotropy energy density K_u ^FL= 1 x 10⁷erg / cc, Curie temperature T_c ^FL= 450K.
[0139]
The hysteresis loop in the state where the functional layer 12 and the recording layer 11 are laminated is as schematically shown in FIG. 5, and antiferromagnetic coupling is obtained.
[0140]
This was subjected to the same magnetic recording experiment as described above. As a result, almost the same result was obtained except that the maximum reproduction signal intensity was obtained at the recording temperature Tw = 430K to 560K. Since the recording layer 12 has a magnetic crystal grain size as small as 5 nm, the presence of a reproduction signal was confirmed even at a very high frequency of 1200 kfci. This means that this medium can perform ultra-high density magnetic recording.
[0141]
Similar samples were made with varying interlayer material and thickness. The attempted interlayer materials are Ru, Re, Rh, Ir, Tc, Au, Ag, Cu, Si, Fe, Ni, Pt, Pd, Cr, Mn, and Al. In all of these, the film thickness showing antiferromagnetic coupling was confirmed in a film thickness region of 5 nm or less.
[0142]
In either case, the oxide layer, SiO₂As a result, a hysteresis loop suggesting a large exchange coupling energy as compared with the Ti alloy layer was obtained. In particular, when Ru, Re, Rh, and Ir were examined in detail, the exchange coupling energy surface density was 1 erg / cm.²~ 5erg / cm²It was found that
[0143]
Similarly, it has been found that antiferromagnetic exchange coupling is also obtained when an intermediate layer is formed of a semiconductor and a material doped with a magnetic substance in the semiconductor. Here, the semiconductors are Si, Ge, Sn, Te, AlP, GaN, GaP, GaAs, InSb, ZnO, ZnS, and ZnTe, and the magnetic materials are Co, Fe, Ni, Mn, and Cr.
[0144]
The reason for the induction of antiferromagnetic coupling is not well understood, but is probably due to superexchange interaction between minority carriers in the semiconductor and the doped magnetic material. Accordingly, the base material to be doped may be any semiconductor as long as it can generate a minority carrier, and the magnetic material is not limited to the above.
[0145]
Next, another example according to the first embodiment will be described.
[0146]
First, on a 2.5-inch glass substrate 13, a base layer (not shown) made of FeTaC soft magnetism is 30 nm thick, a Ti blocking layer (not shown) is 5 nm thick, and a Pt base layer (not shown). ) 10 nm in thickness, [Co layer (thickness 0.23 nm) / Pt layer (thickness 0.87 nm)]₁₀Functional layer 12 and Rh intermediate layer (not shown) having a thickness of 0.8 nm, [Co layer (thickness 0.35 nm) / Pt layer (thickness 0.43 nm)]₆The recording layer 11 and the C protective layer 14 were sequentially laminated by a thickness of 3 nm, and then a lubricant was applied.
[0147]
The functional layer 12 is formed by laminating a laminated structure including a Co layer having a thickness of 0.23 nm and a Pt layer having a thickness of 0.87 nm ten times. The recording layer 11 is formed by laminating a laminated structure composed of a Co layer having a thickness of 0.35 nm and a Pt layer having a thickness of 0.43 nm six times.
[0148]
When the fine structure of the recording layer 11 of the magnetic recording medium thus formed was examined using a TEM, columnar magnetic crystal particles (diameter of about 7 nm) mainly composed of a multilayer film of Co and Pt were physically found. A fine structure divided into two was observed. Although the intergranular substance could not be identified, it is assumed that the constituent material is amorphous Co-O.
[0149]
In addition, the magnetic characteristics of the recording layer 11 and the functional layer 12 alone have a main axis of easy magnetization in the perpendicular direction, and the magnetic anisotropy energy density Ku is 1 × 10 both from VSM measurement and magnetic torque measurement.⁷estimated to be erg / cc. The Curie temperature Tc was estimated to be about 900 K for the recording layer 11 and about 520 K for the functional layer 12.
[0150]
The hysteresis loop in the state where the functional layer 12 and the recording layer 11 are laminated is as schematically shown in FIG. 5, and antiferromagnetic coupling is obtained.
[0151]
This was subjected to the same magnetic recording experiment as described above. As a result, almost the same result was obtained except that the maximum reproduction signal intensity was obtained in a wide range of recording temperatures Tw = 400K to 600K. Since this magnetic recording medium has a small difference in magnetic anisotropy energy density Ku between the recording layer 11 and the functional layer 12, it can be imagined that the thermal fluctuation acceleration phenomenon of the heating portion is suppressed, resulting in a wide temperature margin. The
[0152]
Next, a sample in which the intermediate layer of this magnetic recording medium was amorphous ZnSe was prepared. Antiferromagnetic exchange coupling was obtained.
[0153]
FIG. 6 shows the reversal magnetic field H of the magnetic recording medium thus formed._c ^totalThe temperature dependence of is shown.
[0154]
As shown in FIG._c ^totalIs the Curie temperature T of the functional layer 12 from the room temperature Ta_c ^FLIt decreases rapidly so as to draw a convex curve up to.
[0155]
This is because the temperature dependence of the exchange coupling energy is the Curie temperature T of the functional layer 11._c ^FLUnlike the example shown in FIG. 3, which decreases almost linearly toward the Curie temperature, the Curie temperature T of the functional layer 11_c ^FLThis is an effect obtained by using a semiconductor as an intermediate layer.
[0156]
It has been confirmed that the same effect occurs when the semiconductor used as the intermediate layer is Si, Te, Ge, ZnO, or ZnTe. Moreover, when this intermediate layer was doped with Co, the exchange coupling energy tended to increase.
[0157]
Among them, a magnetic recording medium using a ZnSe layer as an intermediate layer was subjected to the same magnetic recording experiment as described above. As a result, the temperature margin expands to 50K on the high temperature side, and the Curie temperature T of the recording layer 11_c ^RLIt was found that cross-erasing hardly occurred even when the laser was irradiated at a level of.
[0158]
Next, a magnetic recording medium having the same structure as described above was produced. However, the functional layer 12 is [Co layer (thickness x nm) / Pt layer (thickness 0.9 nm)].₆[Co layer (thickness 0.28 nm) / Pt layer (thickness 0.43 nm)]₁₀Various x (magnetic anisotropy energy density K of the functional layer 12 with respect to the recording layer 11_u ^FLThe results of the heat-assisted magnetic recording in the case of the difference in
[0159]
The fine structure of the recording layer 11 of this magnetic recording medium was the same as described above. Further, only a sample in which the recording layer 11 and the functional layer 12 are antiferromagnetically coupled was selected and subjected to a recording / reproducing test. The medium heating temperature Tw is the Curie temperature T of the functional layer 12._c ^FLIt was set to be close.
[0160]
FIG. 7 shows the results of this recording / reproduction test.
[0161]
FIG. 7 shows a carrier-noise ratio (CNR) when a single frequency signal recorded at 600 kfci is reproduced. The CNR is only about 50 dBm at the maximum, and this seems to be because the relationship between the recording / reproducing system, particularly the heating timing and the recording magnetic field application time, is not optimized. However, even at this level, the suitability of heat-assisted magnetic recording can be sufficiently determined.
[0162]
As is clear from FIG._u ^FL/ K_u ^RLA sufficiently large signal was obtained at 0.1 or more. The reason why such characteristics are obtained is that the magnetic anisotropic energy density K of the functional layer 11 is_u ^FLIf it is too small, the magnetic anisotropy energy density Ku of the entire magnetic recording medium is lowered, so that the thermal fluctuation resistance is lowered, and fatal thermal fluctuation deterioration is caused even by heating at the recording temperature. Of course, if the recording temperature is set lower than Tw, the thermal fluctuation deterioration can be suppressed._u ^FL/ K_u ^RLWas less than 0.1, heat assisted recording was possible, and it was confirmed that a CNR exceeding 30 dBm was actually obtained even in this system.
[0163]
Next, a magnetic recording medium having the same structure as described above was produced. However, the functional layer 12 is [Co layer (thickness x nm) / Pt layer (thickness 0.9 nm)].₆The recording layer 11 is [Co layer (thickness 0.28 nm) / Pt layer (thickness ynm)].₁₀X and y were changed (the magnetic anisotropy energy density K of the functional layer 12 respectively)_u ^FLAnd the Curie temperature T of the recording layer 11_c ^RLMagnetic recording media) (corresponding to the difference). The fine structure of the recording layer 11 was the same as described above, and only the sample in which the recording layer 11 and the functional layer 12 were antiferromagnetically coupled was selected and subjected to a recording / reproduction test.
[0164]
The same heat-assisted magnetic recording as described above was performed on the magnetic recording medium thus prepared by changing the irradiation laser power. The medium temperature for each power was estimated by heat conduction analysis simulation.
[0165]
The result is shown in FIG. The horizontal axis is the medium heating temperature, and the vertical axis is the CNR.
[0166]
As shown in FIG. 8, when the horizontal axis is plotted with temperature, no correlation was found, but the Curie temperature T of the recording layer 11_c ^RLA strong correlation was found when the values were normalized by. From this result, the recording temperature is Tw / T_c ^RLIt has been found that a sufficient reproduction signal can be obtained in a region where is less than 0.75. The variation in the signal intensity in this region corresponds to the fact that the recording power is not necessarily the optimum value, but Tw / T_c ^RLThe signal intensity in the region where is larger than 0.75 is obviously smaller than that in the low temperature region.
[0167]
Magnetic anisotropic energy density K of recording layer 11 alone_u ^RLIs its Curie temperature T_c ^{RL L}Tw / T because it decreases linearly toward_c ^RLIs greater than 0.75 is the magnetic anisotropy energy density K_u ^RLIs a region that is less than ¼ of the room temperature value.
[0168]
The reason why the signal intensity becomes extremely small in this region is that, as described above, the magnetic anisotropic energy density K of the recording layer 11 alone._u ^RLThis is probably due to the acceleration of thermal fluctuations due to the drop in
[0169]
For the results obtained in FIG. 8, the recording temperature at which the largest CNR was obtained was selected for each sample._c ^FL/ T_c ^RLI tried plotting against. The result is shown in FIG.
[0170]
As shown in FIG._c ^FL/ T_c ^RLIt has been found that a sufficient reproduction signal can be obtained when is less than 0.75. As described above, when there is no thermal fluctuation deterioration of the recording layer 11, the condition for obtaining the maximum CNR is that the recording temperature is the Curie temperature T of the functional layer 12._c ^FLThis is the case in the vicinity.
[0171]
Magnetic anisotropic energy density K of recording layer 11 alone_u ^RLIs its Curie temperature T_c ^RLDecreases linearly toward T,_c ^FL/ T_c ^RLIs greater than 0.75 is the Curie temperature T of the functional layer 12_c ^FLMagnetic anisotropy energy density K_u ^RLIs less than ¼ of the room temperature value. At this time, the Curie temperature T of the functional layer 12 where a large signal intensity is expected._c ^FLIn the vicinity of heating, the recording layer 11 deteriorates due to thermal fluctuation, so that the signal becomes smaller. As a result, only recording by heating at a lower temperature can be performed.
[0172]
(Reference example)
  next,Reference exampleThe magnetic recording apparatus according to the above will be described.
[0173]
  This magnetic recording device is formed on a nonmagnetic substrate and a nonmagnetic substrate, and the amount of magnetization at room temperature.Than the amount of magnetization at the recording temperature TwA functional layer made of a small ferrimagnetic material, and a functional layer on the functional layerFerromagnetic exchange coupling interactionA recording layer composed of magnetic particles laminated so as to exert a nonmagnetic material formed between the magnetic particles, a functional layer, andRecording layerAnd a magnetic recording means for recording signal magnetization by applying a magnetic field to the recording layer.
[0174]
The magnetic recording apparatus according to the first embodiment shown in FIG. 2 differs from the magnetic recording device according to the first embodiment in that the functional layer 12 is a ferrimagnetic material and the functional layer 12 and the recording layer 11 are ferromagnetically exchange coupled. It is the same.
[0175]
The present invention is characterized in that the magnetization of the functional layer 12 as viewed from the recording layer 11 increases with temperature. In general, since the magnetization of a magnetic material decreases with temperature, the antiferromagnetic coupling is used in the first embodiment to obtain this effect.
[0176]
  On the contraryReference exampleThe feature is that the functional layer 12 itself uses a ferrimagnetic material having a characteristic that magnetization increases with temperature, and the functional layer 12 and the recording layer 11 are coupled by ferromagnetic coupling.
[0177]
Ferrimagnetism is generally found in systems in which two spins of different effective sizes are antiferromagnetically coupled. This state is schematically shown in FIG.
[0178]
As shown in FIG. 10, in the ferrimagnetic material, the spins U and L are coupled in the opposite directions and the Curie temperatures thereof are different, so the temperature change of magnetization is not uniform. In particular, a combination of a spin L having a high saturation magnetization Ms and a low Curie temperature Tc and a spin U having a low saturation magnetization Ms and a high Curie temperature Tc has a characteristic that the magnetization increases with temperature.
[0179]
Therefore, by using the ferrimagnetic material having the characteristic that the magnetization increases when the temperature rises as the functional layer 12 and using the recording layer 11 that is ferromagnetically exchange coupled with the functional layer 12, the same effect as the characteristic shown in FIG. 3 is obtained. Show.
[0180]
FIG. 11 shows the saturation magnetization M of the functional layer 12 at this time._s ^FLAnd magnetic anisotropy energy density K of recording layer 11_u ^RL, Total reversal magnetic field H_c ^totalThe temperature change of is shown.
[0181]
Saturation magnetization M of functional layer 12_s ^FLWith increasing magnetic field H_c ^totalDecreases steeply with respect to temperature than the recording layer 11 originally has. As a result, similarly to the first embodiment, a thermal recording medium that is less susceptible to accelerated deterioration due to thermal fluctuations and is less affected by a demagnetizing field can be obtained.
[0182]
The only essential condition for obtaining the action shown in FIG. 11 is that the magnetization amount (net moment) of the functional layer 12 is larger at a higher temperature than at room temperature. The magnitude relationship between the Curie temperature of the functional layer 12, the Curie temperature of the recording layer 11, and the recording temperature is arbitrary.
[0183]
In the magnetic recording apparatus according to the present invention, the functional layer 12 is made of a rare earth and a transition metal alloy. Examples of ferrimagnetism include amorphous rare earth and transition metal alloy thin films such as TbFe, TbFeCo, TbCo, GdTbFeCo, GdDyFeCo, NdFeCo, NdTbFeCo, and CrPt.₃In particular, amorphous rare earth (RE) and transition metal (TM) alloy thin films have been put to practical use as magneto-optical (MO) recording media, and rare earth rich compositions, compensation compositions, or transition metal rich compositions. However, the vicinity of the compensation composition is preferable because the characteristic that magnetization easily increases with temperature as shown in FIG. 10 can be obtained.
[0184]
The magnetic recording device according to the present invention has a laminated structure in which the functional layer 12 is laminated so that the first functional layer, which is a magnetic material, and the second functional layer, which is a magnetic material, are antiferromagnetic exchange coupled, In addition, the Curie temperature is different between the first functional layer and the second functional layer, and the laminated structure is repeated one or more times. By doing so, a material exhibiting ferrimagnetism can be obtained artificially.
[0185]
A first functional layer that is a magnetic material (typically Co, Ni, Fe, or an alloy thereof) and a second functional layer that is another magnetic material are laminated in this order, In a multilayer film in which the structure is repeated one or more times, antiferromagnetic exchange coupling interaction works between the first functional layer and the second functional layer, and the magnetic characteristics of the first functional layer and the second functional layer are shown. 11 can be used as the same ferrimagnetic functional layer as described above. In order to make the antiferromagnetic exchange coupling interaction work, for example, a non-magnetic layer of 5 nm or less (for example, Ru, Re, Rh, Ir, Tc, Au, Ag, Cu, Mn, Si, Cr or alloys thereof) Alternatively, an oxide) may be inserted between the first functional layer and the second functional layer.
[0186]
Also, what is called an antiferromagnetic material may exhibit ferrimagnetism depending on conditions such as temperature conditions and crystal orientation planes, and in such a case, this can also be used as a functional layer.
[0187]
As a material exhibiting antiferromagnetism, there is a thinned antiferromagnetic material having a Neel temperature higher than room temperature. For example, an alloy of Fe, Cr, Co, specifically, MnNi, MnPd, MnPt, CrPd, CuMn, AuMn, AuCr, CrMn, CrRe, CrRu, FeMn, CoMn, FeNiMn, CoMnFe, IrMn, etc. Alloys, specifically AuMn, ZnMn, FeRh, FeRhIr, Au₂Mn, Au₅Mn₁₂, Au₄Cr, NiMn, PdMn, PtMn, PtCr, PtMn₃, RhMn₃In addition to this, Mn₃PtN, CrMnPt, PdPtMn, NiO, CoO and the like are known.
[0188]
The magnetic recording apparatus according to the present invention is characterized in that the laminated structure of the functional layer 12 and the recording layer 11 is laminated one or more times. The pair of the functional layer 12 and the recording layer 11 described so far need not be a pair. For example, a configuration of substrate / underlayer / functional layer / recording layer / functional layer / recording layer may be used.
[0189]
In such a case, since the interface per recording layer or per functional layer is doubled, there is an advantage that the exchange coupling energy is substantially doubled. The advantages brought about by the increased exchange coupling energy are as described above.
[0190]
In this case, since the total film thickness tends to increase, it is preferable that the functional layer or recording layer constituting the laminated structure is thin.
[0191]
  next,Reference exampleThe magnetic recording medium according to the above will be specifically created.
[0192]
First, an SiN underlayer (not shown) is formed on a 2.5-inch glass substrate 13 with a thickness of 50 nm and Tb.₂₂(Fe₈₅Co₁₅) The functional layer 12 has a thickness of 15 nm, [Co layer (thickness 0.28 nm) / Pt layer (thickness 0.43 nm)]₁₀The recording layer 11 and the C protective layer 14 were sequentially laminated by a thickness of 3 nm, and then a lubricant was applied. At this time, the functional layer 12 and the recording layer 11 were continuously deposited without breaking the vacuum. In addition, the recording layer 11 is formed by laminating 10 layers of a laminated structure including a Co layer having a thickness of 0.28 nm and a Pt layer having a thickness of 0.43 nm.
[0193]
When the fine structure of the recording layer 11 of the magnetic recording medium thus formed was examined using TEM, columnar magnetic crystal grains (diameter of about 7 nm) mainly composed of a multilayer film of Co and Pt were physically found. A fragmented microstructure was observed. Although the intergranular substance could not be identified, it is assumed that the constituent material is amorphous Co-O.
[0194]
The magnetic characteristics of the recording layer 11 and the functional layer 12 alone have a main axis of easy magnetization in the perpendicular direction, and the magnetic anisotropy energy density of the recording layer 11 is K by VSM measurement and magnetic torque measurement._u ^RL= 1 x 10⁷erg / cc. Since the functional layer 12 is close to the compensation composition, it is difficult to evaluate the magnetic anisotropy energy density._u ^FL= 6 × 10⁶estimated to be erg / cc. The Curie temperature is such that the recording layer 11 has T_c ^RL= About 900K, functional layer 12 is T_c ^FL= Estimated to be about 600K.
[0195]
FIG. 12 shows a hysteresis loop in a state where the functional layer 12 and the recording layer 11 are laminated.
[0196]
As shown in FIG. 12, this hysteresis loop was shifted to the plus magnetic field side in one stage. This is because the functional layer 12 and the recording layer 11 are ferromagnetic exchange coupled, and the functional layer 11 does not reverse magnetization with a compensation composition.
[0197]
In FIG. 12, the spin directions of the functional layer 12 and the recording layer 11 are schematically shown. The upper side is the recording layer 11 and the lower side is the functional layer 12.
[0198]
The spin direction of the functional layer 12 is set for the conditions at the time of film formation or for other reasons, and because of the compensation composition, magnetization reversal does not occur (the direction does not change) in the measurement magnetic field range (for example, 20 kOe). When the magnetic field is negatively large, the spins of the functional layer 12 and the recording layer 11 face downward according to the external magnetic field. As the magnetic field strength in the positive direction increases, the upward force of the spin of the recording layer 11 increases, but since it receives a large downward force due to the ferromagnetic exchange coupling force from the functional layer 12, it does not easily reverse. Still a large magnetic field H₁Under magnetization reversal.
[0199]
This state is shown in the upper right part of FIG. If the external magnetic field is reduced from this point to the minus side, the external field directing the spin of the recording layer 11 disappears, but inversion does not occur even under zero magnetic field due to the anisotropic energy of the recording layer 11. . However, since it is constantly receiving downward force due to the ferromagnetic exchange coupling force, H₁Smaller magnetic field H₂Cause inversion. Therefore, it can be seen that this medium has ferromagnetic exchange coupling due to such hysteresis.
[0200]
This hysteresis loop measurement is performed by changing the temperature.₁As a result of examining the temperature change, the switching magnetic field H schematically shown in FIG._c ^totalIt was found that it has the following characteristics.
[0201]
Also, the saturation magnetization of the functional layer 12 is as schematically shown in FIG. These characteristics are brought about by the fact that the functional layer 12 and the recording layer 11 are ferromagnetic exchange coupled, and that the magnetization of the functional layer 12 increases from room temperature toward the high temperature region.
[0202]
The dynamic characteristics of the magnetic recording medium were evaluated with a HDD recording / reproduction evaluation apparatus. The rotational speed was 4500 rpm, the recording gap was 200 nm, and the reproducing head using the GMR element had a gap of 110 nm. The magnetic spacing was estimated to be 30 nm from the flying height and the lubricant thickness. A laser with a wavelength of 633 nm was used for local heating. The laser was applied to the functional layer / switching layer / recording layer portion from the back surface of the substrate via an external low floating lens. The design was made so that both the external low-levitation lens and the substrate were SIL lenses, and the focal point was formed by the functional layer / switching layer / recording layer portion. The diameter of the laser spot is about 500 nm in FWHM. By driving the head with a precise piezo element, the light irradiation position and the gap position of the recording head were matched.
[0203]
First, magnetic recording was attempted without laser irradiation. It was found that the reproduced signal was mostly noisy and sufficient recording was not possible. This is a natural result considering the coercive force of the recording layer 11 and the recording capability of the recording head 1.
[0204]
Next, recording was performed while irradiating a laser. As a result of 400 kfci single frequency recording, the recording temperature Tw is T_peakThe maximum CHR was obtained near
[0205]
Further, similar magnetic property evaluation and recording / reproducing experiments were performed by changing the Tb composition. In the so-called RE-rich composition having a larger Tb composition than FeCo, the temperature change of the magnetic characteristics was the same as in FIG. 11, and it was confirmed that heat-assisted magnetic recording was possible in all the investigated compositions.
[0206]
On the other hand, it was found that the so-called TM rich composition with a small Tb composition has two cases as shown in FIGS.
[0207]
13 is TM rich but close to the compensation composition, and FIG. 14 is far from the compensation composition. As a result of the recording / reproducing test, only the sample having the characteristics as shown in FIG. 13 was able to perform the heat-assisted magnetic recording. This indicates that heat-assisted magnetic recording is possible only when the temperature change of magnetization increases from room temperature toward a high temperature region.
[0208]
This is because the magnetization of the functional layer 12 increases as the temperature rises, and the apparent magnetization of the exchange-coupled functional layer 12 and the recording layer 11 also increases, resulting in a decrease in coercive force and recording. When the functional layer 12 in which the magnetization does not increase is used, the magnetization of the two-layer film of the functional layer 12 and the recording layer 11 also decreases with temperature, so the coercive force cannot be decreased more rapidly than in the case of a single recording layer.
[0209]
Further, the functional layer 12 is made of CrPt.₃A sample was also prepared. The temperature dependence of the magnetic characteristics was the same as in FIG. 11, and it was found that thermally assisted magnetic recording is possible. Thus, the heat-assisted magnetic recording according to the present invention is possible because the functional layer 12 is ferromagnetic exchange coupled and the saturation magnetization thereof increases with temperature. It turns out that it doesn't stop by nature.
[0210]
A magnetic recording medium similar to the above was prepared. However, the functional layer 12 has Co as the first functional layer.₉₀Cr₁₀The layer (thickness: 0.6 nm), the Ru layer (thickness: 0.75 nm), and the Co layer (thickness: 0.25 nm) and Ru layer (thickness: 0.75 nm) as the second functional layer are stacked. What was laminated | stacked twice was used.
[0211]
It was confirmed from the hysteresis loop that the functional layer 12 has a magnetic structure in which the CoCr magnetic layer and the Co magnetic layer are antiferromagnetically coupled.
[0212]
The CoCr magnetic layer alone has a Curie temperature of about 500K, and the Co magnetic layer alone has a Curie temperature of 1200K. Therefore, the temperature dependence of the magnetic characteristics of the functional layer 12 alone is due to the difference in Curie temperature, so that the CoCr dominant at room temperature becomes the Co dominant in the high temperature region, and the ferrimagnetism as shown in FIG. Show. Therefore, it can be used for a heat-assisted magnetic recording medium exactly as described above.
[0213]
Several samples with different thicknesses of the first functional layer and the second functional layer were prepared, and a recording / reproducing experiment similar to the above was performed. As a result, it was found that heat-assisted magnetic recording is possible only for a sample having a saturation magnetization value at room temperature of the first functional layer having a low Curie temperature higher than that of the second functional layer. This is because the success or failure of the heat-assisted magnetic recording is essentially caused by the fact that the magnetization of the functional layer 12 increases with temperature.
[0214]
【The invention's effect】
As described above, according to the present invention, magnetic recording can be performed without causing remagnetization reversal due to acceleration of thermal fluctuation.
[Brief description of the drawings]
FIG. 1 is a perspective view of a magnetic recording apparatus according to the present invention.
FIG. 2 is a cross-sectional view of a magnetic recording apparatus according to the present invention.
FIG. 3 is a diagram schematically showing changes in magnetic anisotropy and reversal magnetic field of the recording layer and functional layer of the magnetic recording apparatus according to Embodiment 1 of the present invention with respect to the medium temperature.
FIGS. 4A and 4B are diagrams schematically showing changes in magnetization of the recording layer and the functional layer of the magnetic recording apparatus according to Embodiment 1 of the present invention with respect to heat application, in which FIG. ) Is during heat application, and (d) is after heat application.
FIG. 5 is a diagram schematically showing a hysteresis loop of the magnetic recording apparatus according to the first embodiment of the invention.
FIG. 6 is a diagram schematically showing changes in magnetic anisotropy of a recording layer and a functional layer and a reversal magnetic field with respect to the medium temperature in another example of the magnetic recording apparatus according to Embodiment 1 of the present invention.
FIG. 7 is a diagram showing a change in CNR with respect to KuFL / KuRL in another example of the magnetic recording apparatus according to the first embodiment of the present invention.
FIG. 8 is a diagram showing a change in CNR with respect to Tw / TcRL in another example of the magnetic recording apparatus according to the first embodiment of the present invention.
FIG. 9 is a diagram showing a change in CNR with respect to TcFL / TcRL in another example of the magnetic recording apparatus according to the first embodiment of the invention.
FIG. 10Reference exampleFIG. 6 is a diagram showing the relationship between the magnetization and temperature of the functional layer of the magnetic recording apparatus in FIG.
FIG. 11Reference exampleFIG. 6 is a diagram schematically showing changes in magnetic anisotropy of a recording layer and a functional layer and a reversal magnetic field with respect to the medium temperature of the magnetic recording apparatus in FIG.
FIG.Reference exampleThe figure which shows typically the hysteresis loop of the magnetic recording medium in.
FIG. 13Reference exampleFIG. 6 is a diagram schematically showing changes in magnetic anisotropy, switching magnetic field, and magnetization of a recording layer and a functional layer with respect to a medium temperature in another example of the magnetic recording apparatus in FIG.
FIG. 14Reference exampleFIG. 6 is a diagram schematically showing changes in magnetic anisotropy, switching magnetic field, and magnetization of a recording layer and a functional layer with respect to a medium temperature in a comparative example of the magnetic recording apparatus in FIG.

Claims (7)

A non-magnetic substrate;
A functional layer formed on the non-magnetic substrate and made of a magnetic material having a Curie temperature Tc ^FL and a magnetic anisotropic energy density Ku ^FL ;
The Curie temperature Tc ^RL higher than the Curie temperature Tc ^FL laminated so as to exert an antiferromagnetic exchange coupling interaction with the functional layer on the functional layer, and a magnetic anisotropy energy of 5 × 10 ⁶ erg / cc or more A recording layer comprising magnetic particles having a density Ku ^RL and a non-magnetic material formed between the magnetic particles;
Heating means for heating the functional layer and the recording layer to a recording temperature Tw higher than room temperature and below Tc ^FL ;
A magnetic recording apparatus comprising: magnetic recording means for recording signal magnetization by applying a magnetic field to the recording layer. 2. The magnetic recording apparatus according to claim 1, wherein the magnetic anisotropy energy density Ku ^FL at room temperature is equal to or less than the magnetic anisotropy energy density Ku ^RL . 3. The magnetic recording apparatus according to claim 2, wherein the magnetic anisotropy energy density Ku ^FL at room temperature > the magnetic anisotropy energy density Ku ^RL × 0.1. 4. The magnetic anisotropy energy density Ku ^RL at the recording temperature Tw is greater than ¼ of the anisotropic energy density Ku ^RL at room temperature. 5. Magnetic recording device. According to any one of claims 1 to 4 wherein the magnetic anisotropic energy density Ku ^RL in the Curie temperature Tc ^FL being greater than 1/4 of the magnetic anisotropy energy density Ku ^RL at room temperature Magnetic recording device. 6. The magnetic recording apparatus according to claim 1, further comprising a nonmagnetic intermediate layer having a thickness of 5 nm or less between the recording layer and the functional layer. The nonmagnetic intermediate layer is selected from at least Ru, Re, Rh, Ir, Tc, Au, Ag, Cu, Si, Fe, Ni, Pt, Pd, Cr, Mn, Al, a semiconductor and a semiconductor doped with a magnetic substance. The magnetic recording apparatus according to claim 6, wherein the magnetic recording apparatus is made of a

Images