JPH0528485A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce a magnetic recording medium having excellent over write characteristic. CONSTITUTION:The Cr base layer 2 is film formed on a non-magnetic substrate 1 by sputtering method and the magnetic layer 3 made from Co alloy having uniaxial crystal magnetic anisotropy is laminated and film formed on the base layer 2. In the production method of the magnetic medium, when the magnetic layer 3 is film formed, negative bias potential is impressed on the substrate 1 and potential quantity is regulated larger in order from the substrate 1 side to the surface side when film forming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium used in a magnetic disk device, and more particularly to a method for improving overwrite characteristics.

[0002]

2. Description of the Related Art In recent years, with the increasing recording density of magnetic recording media, a thin film (magnetic layer) of a Co alloy having uniaxial crystal magnetic anisotropy such as CoNiCr and CoCr is formed on a non-magnetic substrate by sputtering. The metal thin film type magnetic recording medium is used. In order to achieve high density recording in the magnetic recording medium, it is necessary to have a high coercive force.
As a method of improving the coercive force, a method of applying a negative bias voltage to the substrate at the time of forming the magnetic layer has been proposed, as disclosed in JP-A-2-154322.

[0003]

However, in the magnetic recording medium formed by these methods, the overwrite characteristics (referred to as overwrite characteristics and O / W characteristics) are not taken into consideration, and the O / W characteristics are not taken into consideration. I had a problem with.
That is, the magnetomotive force of the magnetic head decreases from the surface side (head facing surface side) of the magnetic recording medium to the substrate side, but since the coercive force is high even under the magnetic layer, the magnetomotive force of the magnetic head decreases. Together, a new pattern (information)
However, there is a problem that it becomes difficult to write to the lower part, and the S / N of the new pattern deteriorates due to the noise caused by the residual of the previous pattern.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a magnetic recording medium having good overwrite characteristics.

[0005]

[Means for Solving the Problems] By sputtering,
In a method of manufacturing a magnetic recording medium, a Cr underlayer is formed on a non-magnetic substrate, and a magnetic layer made of a Co alloy having uniaxial crystal magnetic anisotropy is laminated on the underlayer. A negative bias voltage is applied to the substrate during film formation, and the magnitude of the voltage is increased as the film is formed closer to the front surface side than the substrate side.

[0006]

When a negative bias voltage is applied to the substrate, the crystal orientation of the Co alloy film forming the magnetic layer is improved, and Co
Grain boundary segregation of Cr in the alloy film is promoted, and isolation of the high-concentration Co alloy is promoted. Therefore, the coercive force is improved.
When forming the magnetic layer, by setting the magnitude of the bias voltage when forming the magnetic layer on the surface side larger than that when forming the magnetic layer on the substrate side, as a magnetic layer A film having a large coercive force is formed toward the surface side, and the overwrite characteristic is improved.

[0007]

EXAMPLES The production of the magnetic recording medium shown in FIG. 1 will be described below as an example. In this medium, a Cr underlayer 2 is formed on a nonmagnetic substrate 1, a magnetic layer 3 made of a Co alloy having uniaxial crystal magnetic anisotropy is formed thereon, and a protective layer is further formed thereon. Layer 4 is formed.

FIG. 2 shows an example of a sputtering apparatus for carrying out the present invention, in which a target 22 for emitting film-forming atoms of a Co alloy layer or a Cr layer is installed under a vacuum chamber 21. A ring-shaped anode 23 is attached around it, and a negative voltage (generally -1 KV or less) is applied by a sputtering power source 24. On the other hand, a holder 25 for attaching the substrate 1 is provided on the upper portion, and the substrate 1 attached to the holder 25 has a negative voltage (normally , −50 to −300 V) is applied. 27 is an exhaust pipe, which is connected to a vacuum pump by a pipe, and 28 is a sputtering supply pipe for Ar gas or the like.

Any sputtering apparatus can be used as long as it can apply a negative voltage to the substrate. For example, in order to improve the uniaxial orientation of the magnetic layer, a heater for heating the substrate may be additionally provided in the vacuum container. Alternatively, a magnetron sputtering device having a magnet on the back surface of the target may be used. Further, the power supply for sputtering and the bias power supply are not limited to direct current, and a high frequency (RF) power supply may be used.

The sputtering conditions will vary depending on the sputtering apparatus used, the substrate, the target material, etc., but generally the Ar gas partial pressure is 1 to 10 × 10 ⁻³ Torr, and the substrate temperature is 150 to
It is set to about 300 ℃. As the substrate 1, a substrate on which an amorphous Ni-P plating layer of about 10 to 20 μm is formed on the Al alloy substrate 1 to secure rigidity is usually used, but the substrate 1 is not limited to this. Any non-magnetic material having a certain degree of rigidity such as a glass substrate or a ceramic substrate can be used. Incidentally, the upper surface of the substrate is usually provided with an unevenness process called a texture in order to reduce the contact frictional resistance with the magnetic head.

The Cr underlayer 2 formed on the substrate 1 is
It is formed for in-plane orientation of the c-axis (crystal axis showing crystal magnetic anisotropy) of a Co alloy (crystal structure hcp) having uniaxial crystal magnetic anisotropy formed thereon, It is formed by sputtering to a thickness of about 500 to 2000Å. A negative bias voltage may be applied to the substrate when the Cr underlayer is formed.

The Co alloy forming the magnetic layer 3 may be any alloy having uniaxial crystal magnetic anisotropy. For example, in a CoCrX alloy, X is V, Ni, Zr, Nb, Mo, Rn, Rh, Hf, T
It is possible to use one containing at least one of a, W, Re and Pt. The Cr content is 5-16
wt% is good. If it is less than 5% or more than 16%, the c-axis of the Co alloy shifts from random orientation to in-plane orientation,
This is because the coercive force and the squareness ratio (Br / BS) are lowered, which causes deterioration of electrical characteristics.

When forming the magnetic layer 3, the negative bias voltage applied to the substrate 1 is gradually increased continuously or stepwise toward the surface side. As a result, the coercive force of the magnetic layer 3 on the substrate side can be weakened and the coercive force on the surface side can be increased, and the overwrite characteristic can be improved.
The layer thickness of the magnetic layer 3 is usually about 600 to 800 Å. This is because a magnetic recording medium having a Brδ of 450 to 600 G · μ is required to secure the reproduction output and reduce the medium noise.

A non-magnetic protective layer 4 made of carbon or the like is formed on the magnetic layer 3 by sputtering at a rate of about 200 to 400 Å, and a lubricant such as fluorinated polyether is further provided on the magnetic layer 3 at a rate of about 20 to 50 Å. You may apply. The protective layer 4 and the lubricant coating layer may be formed as needed.
When the magnetic recording medium is industrially produced, the Cr underlayer, magnetic layer, Cr layer, and nonmagnetic protective layer are provided with a sputtering device equipped with a target material for forming a desired layer, and the substrate is used. May be sequentially moved to each sputtering apparatus to form a laminated film.

Next, specific examples will be given. (1) A Ni-P plated layer was formed on an Al substrate, and the surface of the Ni-P plated layer was used. A Cr underlayer 2 of 1000 liter was formed on the Ni-P plated layer as shown in FIG.
On top of that, a Co ₈₆ Cr ₁₂ Ta ₂ alloy of 650 is used as a magnetic layer.
Å The film was formed. At this time, the magnitude of the bias voltage applied to the substrate is shown in FIG. After forming the magnetic layer (Co alloy layer), a carbon layer was further formed thereon in a 250 Å laminated structure. In addition, the magnetic layer of the conventional example is -70V evenly from the lower surface of the underlayer side to the surface.
Was applied.

An RF magnetron sputtering apparatus was used as the film forming apparatus, and the film forming conditions were Ar gas pressure of 5 mmTorr and substrate temperature of 230 ° C.

[0017]

[Table 1]

(2) After film formation, the coercive force (H
c) and O / W (-dB) were investigated. The results are shown in Table 1.
Shown in. (3) From Table 1, it is recognized that the examples are superior in coercive force and O / W characteristics to the conventional examples.

[0019]

As described above, according to the method of manufacturing a magnetic recording medium of the present invention, when the magnetic layer is formed, the magnetic layer is applied to the substrate from the lower surface of the magnetic layer to the surface thereof. Since the negative bias voltage was increased toward the surface side, the coercive force on the substrate side could be made weaker than on the surface side, and the overwrite characteristics could be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a magnetic recording medium according to an example.

FIG. 2 is a structural explanatory view showing an example of a sputtering apparatus for carrying out the present invention.

FIG. 3 is a graph showing a magnitude of a bias voltage when forming a magnetic layer in an example.

[Explanation of symbols]

 1 Substrate 2 Cr Underlayer 3 Magnetic Layer 26 Bias Power Supply

Claims (1)

Claim: What is claimed is: 1. A Cr underlayer is formed on a nonmagnetic substrate by sputtering, and a magnetic layer made of a Co alloy having uniaxial crystal magnetic anisotropy is laminated on the underlayer. In the method of manufacturing a magnetic recording medium for forming a film, a negative bias voltage is applied to the substrate when forming the magnetic layer, and the magnitude of the voltage is increased from the substrate side to the surface side. Method for manufacturing magnetic recording medium.