JPS60160001A - Thin metallic film having its surface protected by carbide - Google Patents

Abstract

PURPOSE:To reduce a danger where an amorphous magnetic material is crystallized in the recording and erasing modes by irradiating a laser beam to a photomagnetic recording medium and reducing the intensity of the laser beam after the inversion of nagnetization is started to continue said inversion. CONSTITUTION:The laser beam of a laser diode light source 2 which is driven by a driving circuit 1 is irradiated to an amorphous magnetic film of a revolving disk recording medium disk via a collimator lens 3, a beam splitter 4 and an objective lens 5. When the invertion of magnetization is started, the intensity of the laser beam is reduced to continue said inversion of magnetization. In this way, a danger where an amorphous magnetic material is crystallized is reduced.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to recording or erasing information on a former magnetic recording medium that is recorded and reproduced using the magnetic Kerr effect or the magnetic Faraday effect. This relates to magneto-optical recording or erasing devices.

(Background of the Invention) In recent years, the information society has progressed at a remarkable pace, and the need for large-capacity recording media and recording/playback methods is rapidly increasing. Laser video discs, digital audio discs, etc. have already been put into practical use. ing. However, the recording media that have been put into practical use have the drawback of not being rewritable, and a rewritable recording medium and recording/reproducing system are desired.

A magneto-optical recording and reproducing method has been proposed as one of the rewritable recording and reproducing methods, and a prototype has also been announced. This magneto-optical recording and reproducing method is, for example, GdCo, G
Applying a strong external magnetic field to a magneto-optical recording medium mainly consisting of a perpendicularly magnetized film made of a magnetic material such as dTbFe, and once aligning the direction of magnetization of this perpendicularly magnetized film either upward or downward, For example, by irradiating a laser beam with a cross-sectional radius of 1 micron, the perpendicularly magnetized film is locally heated to a temperature above or near one point (Tc) of the magnetic material, and the coercive force of the heated area is reduced to zero or extremely small, and at the same time By applying a weak reversal magnetic field, the direction of magnetization is reversed, and since the medium is now moving at high speed, the irradiation position of the laser beam moves every moment, and as a result, an elliptical (ro-co-shaped) bit is formed. It is formed.

The length of the bit is at least 2 microns, assuming a width of 1 micron.

Information is then recorded in the form of the presence or absence of this bit and bit a.

On the other hand, since the direction of magnetization of the bit part of the recorded information is opposite to that of the film, when linearly polarized light is irradiated, the polarization plane of the reflected or transmitted light changes depending on whether the magnetization is above or below the same direction. are reproduced using different phenomena (magnetic Kerr effect or magnetic Faraday effect).

In other words, when the direction of magnetization is upward with respect to the incident light, if the polarization plane of reflected or transmitted light is rotated by θ degrees with respect to the polarization plane of the incident light, then the direction of magnetization is downward with respect to the incident light. No and @ rotate by one θ degree.

Therefore, if a polarizer (also called an analyzer) is placed in front of the reflected or transmitted light so that its main axis is set at -11 degrees, the light from the downwardly magnetized part will hardly pass through the analyzer. First, the source from the upwardly magnetized part will be transmitted by the amount multiplied by sin 2σK, so if you install a detector (photoelectric conversion element) at the end of the analyzer, you can scan the recording medium at high speed. , and is reproduced as a current strength signal depending on the presence or absence of recorded bits and the bit length.

To erase the record, the nine recorded bits are heated with a laser beam in the same way as during recording, thereby reducing the coercive force to zero or an extremely low value, and at the same time applying a reversal magnetic field. By doing so, the magnetization direction of the bit is returned to its original direction, and then the laser beam irradiation is stopped to fix the magnetization direction to the original direction. This erases the recorded bits, thereby erasing the recording and returning the medium to its pre-recording state. Therefore, since re-recording becomes possible, rewriting is completed by performing recording as described above.

By the way, in conventional magneto-optical recording or erasing devices, bits are formed by irradiating a laser beam at the same intensity level for a period of time depending on the bit length, so the relationship between changes in the intensity level of the laser beam and the shape of the formed bit is When shown, it becomes as shown in FIG. 1 (1) and (2).

On the other hand, magnetic materials with large θ such as TbFeCo, D7
For FeCO1'G'dTbF'eCO, etc., one cucumber (
Te) is high, so a high-intensity laser beam is required for recording and erasing.

However, the above-mentioned #K is thick (the daytime magnetic material of Tc has a crystallization temperature higher than Tc, but it is relatively close to
Therefore, when heated too much, there is a tendency for the phase to change from an amorphous state exhibiting perpendicular magnetization to a crystalline state exhibiting no perpendicular magnetization. Therefore, even when recording or erasing is intended, the completely reversed magnetization is no longer 100%, which has the drawback of lowering the S/N ratio or erasing accuracy.

(Object of the invention) Therefore, the object of the present invention is to solve the above-mentioned drawbacks and to
An object of the present invention is to provide a magneto-optical recording or erasing device that reduces the risk of crystallization of an amorphous magnetic material during recording and erasing even in a recording medium using a magnetic material with a high c.

(Summary of the Invention) As a result of intensive research, the inventor of the present invention discovered that, by chance, if the magnetization of a minute portion was successfully reversed by heating initially, then even if the intensity of the laser beam was weakened (in other words, if the laser beam was not heated too much) The inventors discovered that the reversal continues like a chess game, thereby reducing the risk of crystallization of the formed bit part, and thus achieved the present invention'-) Voice.

The reason why the intensity of the laser beam can be weakened after the magnetization is successfully reversed is not fully understood, but it is likely that the exchange interaction from the reversed magnetic moment is caused by the external magnetic field. The present inventor believes that since the magnetic flux acts on the adjacent unreversed magnetic moment, the reversal occurs even when the temperature is not high enough and a considerable amount of coercive force remains.

Therefore, the present invention provides a magneto-optical recording or erasing device that:
Magneto-optical recording or erasing device f: Provided is a magneto-optical recording or erasing device, characterized in that the intensity of the laser beam is lowered after the start of magnetization reversal to continue magnetization reversal to form or erase necessary pits.

The present invention will be explained below with reference to examples, but the present invention is not limited to these examples.

(Embodiment 1) Figure 2' is a schematic diagram showing the overall configuration of a magneto-optical recording or erasing device according to the first embodiment. In the figure, fl) is a light source drive circuit, (2) is a laser diode light source, and (3)
Ha collimator lens, (4) is a beam splinter,
(5) is an objective lens, (6) is a disk-shaped recording medium (
Spindle motor for rotating Disk)k, (
7) is a condenser lens, (8) is an analyzer, and (9) is a detector. If it is only for recording and erasing (7
), (8), and (9) are unnecessary, but since in many cases the same device is used for both reproduction and reproduction, an explanation will be given here using a device that can also be used for reproduction. (Disk) is a disk-shaped recording medium that is not included in the constituent elements of the present invention.

FIG. 3 is a block diagram showing more detailed contents of the drive circuit (1) shown in FIG. 2, and represents a laser diode light source (2) shown in the figure.

Using the apparatus of this example, a magneto-optical recording medium (disc-shaped) with a GdTbFeCo perpendicularly magnetized film as a recording layer was rotated at a continuous linear velocity of 13.2 m while irradiating the medium with a laser beam. , 3000e of external magnetic field was applied, and the information 010]01... was recorded.

Therefore, the intensity of the laser beam was changed as shown in FIG. 4 fi+. In FIG. 4 (1), the initial laser beam intensity during recording #: Pw = 15.6 mW, the reduced laser beam intensity during recording PL = 8.3 mW,
Pulse width during recording tw -;, 5 x 10-' seconds, pulse interval day during non-recording = 5 x 10-' seconds, initial laser beam intensity irradiation time during recording tp = 2 x 3
0-' seconds.

(Example 2) The configuration of the mounting device is almost the same as in Example (Figure 2), but here the reflected light from (Di'fkA) is collected by a condenser lens (7) and sent to a detector (9). An example will be described in which the electrical signals received and converted are used as signals for focusing and tracking.

Focusing and tracking signals are, in principle, always required during tracking, and therefore it is necessary to irradiate a laser beam even when recording or erasing bits. However, the intensity of the laser beam is high enough for recording or erasing.

There's no need to make it expensive.

Therefore, here, the intensity of the laser beam is changed as shown in Figure 5, and at the same time as the bit is formed, a low intensity (PDC) beam is continued to be irradiated even when not forming the bit, and the reflected light is used as a focusing and tracking signal. Make use of it.

On the other hand, an erasing device is in principle the same as a recording device, except that the direction of the external magnetic field is reversed, but when attempting to erase records within a certain range, it picks up only the formed pits. Since it is troublesome to erase, within that range, regardless of the presence or absence of pits, after irradiating the laser beam with the -1-r erasing intensity Pg level as shown in Figure 6 (1), if the reversal starts. For example, according to the present invention, the irradiation is performed at a lower level than the PL level, and then the inversion is continued to complete erasing. In this case, when continuing to irradiate at the PL level,
If it is not reliable whether the reversal continues or not, the laser irradiation intensity may be returned to the original erase intensity PK level from time to time as shown in FIG. 6(2).

(Effects of the Invention) According to the present invention, high strength (Pw
) The time the medium is exposed to the laser beam is shortened, so the risk of crystallization of the amorphous directly magnetized film of the medium is reduced, and as a result, a decrease in the S/N ratio during playback can be avoided. Furthermore, shortening of the life of the medium due to repeated recording and erasing of the medium can be avoided.

In addition, according to the present invention, the high laser beam intensity required for recording or erasing is required for a short time, so an inexpensive low-power semiconductor laser light source (which can emit a high-intensity beam temporarily) can be used. The device can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 (1) is a graph showing changes in laser beam irradiation intensity, and FIG. 1 (2) is a plan view of a bit formed on a recording medium by laser beam irradiation. (
conventional example). FIG. 2 is a schematic diagram showing the overall configuration of a magneto-optical recording or erasing device according to Embodiment 1 of the present invention. The third tooth is a block diagram showing more detailed contents of the drive circuit (1) in FIG. 2. FIG. 4 (1) is a graph showing changes in the irradiation intensity of the laser beam in the apparatus of Example 1, and FIG. 4 (2) is a plan view of pits formed on the recording medium by the irradiation.
(3) is a sequence of numbers indicating corresponding 0 and 1 information. FIG. 5 (1) is a graph showing changes in the irradiation intensity of the laser beam in the apparatus of Example 2, FIG. 5 (2) is a top view, and FIG. This is the sequence of numbers shown. FIGS. 6(1) and 6(2) are graphs showing changes over time in the irradiation intensity of the laser beam during erasing. Applicant: Nippon Kogaku Kogyo Co., Ltd. Agent: Takashi Watanabe

Claims (1)

[Claims] 1. A magneto-optical recording medium is irradiated with a laser beam to locally heat the medium to lower the coercive force of the heated portion, and at the same time a reversal magnetic field is applied to increase the coercive force of the heated portion. 1) In a magneto-optical recording or erasing device that performs recording or erasing by reversing the direction of magnetization, once the intensity of the laser beam has started to be reversed, the intensity of the laser beam is then lowered to prevent reversal of magnetization. A magneto-optical recording or erasing device characterized by forming or erasing bits by continuous operation. 2. The magneto-optical recording according to claim 1, characterized in that the medium is continuously irradiated with low intensity even during recording or erasing in order to obtain the laser beam unevenness, focusing, or tracking signal. erasing device.