JPH076344A - Metallic thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having high coercive force without reducing the saturation magnetization (Ms) of the magnetic recording layer by forming a nonmagnetic underlayer with Cu or a Cu-based Cu alloy. CONSTITUTION:This magnetic recording medium has a nonmagnetic underlayer 2 formed on the nonmagnetic substrate 1 and a magnetic recording layer 3 made of a magnetic layer of a CoSm alloy having high crystal magnetic anisotropy and a nonmagnetic protective layer 4 on the underlayer 2. The underlayer 2 is formed with Cu or a Cu-based Cu alloy and epitaxial growth is carried out so as to enhance the crystal magnetic anisotropy of the magnetic layer 3 formed on the underlayer 2 in the intrasurface direction of the magnetic layer 3. High coercive force can be ensured without reducing the Ms of the magnetic recording layer 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic disk.

[0002]

2. Description of the Related Art In recent years, with the increase in recording density of magnetic recording media, a magnetic layer made of a Co alloy having uniaxial crystal magnetic anisotropy such as CoNiCr and CoCrTa is formed on a non-magnetic substrate with a Cr underlayer interposed therebetween. A metal thin film type magnetic recording medium is used. Conventionally, as a non-magnetic substrate, an amorphous Ni-P plating layer is formed on an A1 alloy plate, and fine irregularities called texture are mechanically processed along the circumferential direction on the surface thereof. It was The mechanical texture reduces friction between the head and the medium, improves CSS (constant start / stop) characteristics, and improves the magnetic anisotropy in the circumferential direction of the Co alloy magnetic layer formed on the surface side thereof. It has the effect of improving the coercive force. On the other hand, in the Cr underlayer, the crystal structure of Cr forming the underlayer is such that the crystal axis (C axis) showing the magnetic anisotropy of the Co alloy magnetic layer formed thereon is in-plane oriented. It acts to improve the coercive force.

Recently, miniaturization and increase in capacity of hard disk devices have been spurred, and development of magnetic recording media in response to them has been required. As the recording density of the magnetic recording medium is increased, the recording bit size is further reduced. Therefore, the flying height of the magnetic head must be reduced as much as possible to increase the read output. For that purpose, it is necessary to promote the smoothing of the non-magnetic substrate on which the magnetic layer is formed to reduce the flying height of the head.

For this reason, a glass substrate is adopted as the non-magnetic substrate in place of the Al alloy / Ni-P plated substrate, and it has a directional texture due to mechanical processing and a non-directional (isotropic) property due to chemical corrosion. Textures are now formed. This is because minute burr-like protrusions are easily formed on the texture formed by mechanical processing, which makes it difficult to reduce the flying height of the head.

However, the non-directional texture due to chemical corrosion cannot be expected to improve the magnetic anisotropy due to the shape effect, so that there has been a limit to increase the coercive force of the magnetic recording medium. Regarding this problem, even if the texture is non-directional by forming the magnetic layer using the CoSm alloy disclosed in Japanese Patent Laid-Open No. Hei 3-23513,
Even by low temperature sputtering, a high coercive force equal to or higher than that of the conventional Co alloy magnetic layer can be obtained.

[0006]

However, when forming a magnetic layer using a CoSm alloy on a Cr underlayer, a diffusion layer is formed at the Cr / CoSm alloy interface, and the saturation magnetization Ms of the magnetic layer decreases. There's a problem. The present invention has been made in view of the above problems, and an object thereof is to provide a metal thin film type magnetic recording medium having a CoSm alloy magnetic layer, which has both high Ms and high coercive force.

[0007]

The magnetic recording medium of the present invention is a metal thin film type in which a nonmagnetic underlayer and a magnetic recording layer having a CoSm alloy magnetic layer are laminated in the same order on a nonmagnetic substrate. In the magnetic recording medium, the non-magnetic underlayer is formed of Cu or a Cu alloy containing Cu as a main component.

[0008]

[Function] When a CoSm alloy layer is formed on a Cu underlayer, a diffusion layer is hardly formed at the Cu / CoSm alloy interface, and CoSm alloy fine crystals (a peak showing crystallinity is not detected by X-ray diffraction). Grows epitaxially on the underlayer, exhibits in-plane magnetic anisotropy, and has a coercive force in the in-plane direction.

As the material of the underlayer, not only pure Cu but also almost no diffusion layer is formed between it and the CoSm alloy.
A Cu alloy containing Cu as a main component may be used, and as the alloying element, an element exhibiting a crystal refining effect or the like can be contained. For example, Cr may be contained at 10 atomic% or less, and even in this case, Ms of the CoSm alloy magnetic layer does not decrease.

[0010]

EXAMPLE FIG. 1 shows a cross-sectional view of a main part of a magnetic recording medium according to an example. A nonmagnetic underlayer 2 is formed on a nonmagnetic substrate 1, and a film is formed thereon. A magnetic recording layer 3 made of a CoSm alloy magnetic layer having a large crystal magnetic anisotropy is formed in the rear surface, and a nonmagnetic protective layer 4 is further laminated and formed thereon by sputtering.

The substrate 1 is made of Al alloy / Ni-P.
Plated substrates, metal substrates such as titanium, and non-metal substrates such as glass, ceramics, carbon, and polymers are used. A texture having fine irregularities is formed on the surface of the substrate 1, but the texture need not be formed along the circumferential direction and may be non-directional. Board 1
As described above, the non-magnetic underlayer 2 formed on the Cu layer is made of Cu.
Alternatively, the crystal magnetic anisotropy in the in-plane direction of the CoSm alloy magnetic layer formed of a Cu alloy containing Cu as a main component and formed on the underlayer 2 is improved. The layer thickness is usually 500 to 2
It is said to be about 000Å

As described above, the magnetic recording layer 3 is formed of a CoSm alloy that can obtain a high coercive force. The Sm content is preferably about 20 at% or less in order to secure a high Ms of about 600 emu / cc or more. still,
The magnetic recording layer is not limited to a predetermined CoSm alloy magnetic layer formed as a single layer as shown in the figure, but a CoSm alloy magnetic layer and a non-magnetic intermediate layer made of Cu or Cu alloy forming Cr or an underlayer. It may be formed by alternately stacking and. The layer thickness of the magnetic recording layer 3 (the layer thickness of a CoSm alloy single layer, the total thickness of a CoSm alloy layer if it is a multiple layer) is usually 200 to
It is about 800Å.

On the magnetic recording layer 3, carbon, Si
The nonmagnetic protective layer 4 made of O ₂ or Cr / SiO ₂ is 2
It is formed to have a thickness of about 00 to 400 Å, and a liquid lubricant such as fluorinated polyether may be further applied thereto on the order of about 20 to 50 Å (single molecular thickness). The protective layer 4 and the lubricating layer may be formed as needed. Non-magnetic underlayer,
The magnetic recording layer and the non-magnetic protective layer are usually formed by sputtering. The sputtering conditions are usually such that the Ar gas partial pressure is 10 to 50 mTorr and the substrate temperature is room temperature to 10
It is set to about 0 ° C.

Next, specific examples will be given. Using a RF ternary sputtering device, Cu or Cu-on a glass substrate that is non-directionally textured by chemical corrosion.
A 5 at% Cr underlayer is formed with various thicknesses, a magnetic recording layer made of a Co-13 at% Sm alloy magnetic layer is formed on the underlayer to 500 Å, and a Cr layer having a film thickness of 100 Å is further formed thereon. A SiO ₂ protective layer was formed into a 150 Å laminated film. The substrate temperature during film formation was kept at room temperature, and the Ar gas partial pressure and high frequency power during film formation were 15 mTorr at the time of film formation of the underlayer.
00W, 160W at 35mTorr when forming magnetic layer, Cr
200 W at 10 mTorr when forming a layer, 15 when forming a protective layer
It was set to 200 W at mTorr.

Using the magnetic recording medium of the obtained example,
The magnetic properties of the medium were measured using VSM under an external magnetic field of 10 kOe. The result is shown in FIG. From FIG. 2, it can be seen that a coercive force of 2000 Oe or more is provided when the underlayer is about 500 Å or more.

[0016]

As described above, in the metal thin film type magnetic recording medium of the present invention, since the non-magnetic underlayer is formed of Cu or a Cu alloy containing Cu as a main component, the diffusion layer is formed on the underlayer. The CoSm alloy film can be epitaxially grown so as to exhibit in-plane magnetic anisotropy with almost no occurrence of the above phenomenon, whereby a high coercive force can be obtained without reducing Ms of the magnetic recording layer.

[Brief description of drawings]

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

FIG. 2 C with Cu or Cu-5 at% Cr underlayer
FIG. 6 is a graph showing the relationship between the underlayer thickness and the coercive force Hc in the magnetic recording medium of the example having the oSm magnetic layer.

[Explanation of symbols]

 1 substrate 2 non-magnetic underlayer 3 magnetic recording layer 4 protective layer

Claims (1)

[Claims] 1. A nonmagnetic underlayer and CoS on a nonmagnetic substrate.
In a metal thin film magnetic recording medium in which magnetic recording layers having an m-alloy magnetic layer are stacked in the same order, the nonmagnetic underlayer is formed of Cu or a Cu alloy containing Cu as a main component. A characteristic metal thin film magnetic recording medium.