JPH06309644A - Metal thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To largely increase the coercive force by forming a CrCu alloy of specified compsn. as a nonmagnetic base layer of a metal thin film type magnetic recording medium. CONSTITUTION:A CrCu alloy containing a specified amt. of Cu in Cr is formed as a nonmagnetic base layer 2 on a substrate 1. The Cu does not make solid solution with Cr but easily precipitate in interlayer spaces of columnar layers of Cr to promote production of fine grains and separation of grains. Thereby, even when the Sm amt. in a CoSm alloy which constitutes the magnetic recording layer 3 is decreased to about <=20% to obtain high Ms as about >=600emu/cc high coercive force can be obtd. and both of high Ms and high coercive force can be obtd. The nonmagnetic base layer 2 contains 0.5-15 atomic % Cu. If the amt. of Cu is smaller than this, the effect to increase the coercive force of the magnetic layer decreases. If the amt. exceeds 15%, the crystalline orientation of the Cr columnar structure decreases to deteriorate orientation effect of the magnetic layer in the plane direction. A nonmagnetic protective layer 4 is formed to have 200-400Angstrom thickness on the magnetic recording layer 3. Thus, the coercive force can be largely improved.

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 acts so as to in-plane align the crystal axis indicating the magnetic anisotropy of the Co alloy magnetic layer formed on the Cr underlayer. It has the effect of improving the magnetic 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,
Also, coercive force equal to or higher than that of the conventional Co alloy magnetic layer can be obtained by low temperature sputtering.

[0006]

[Problems to be Solved by the Invention] However, CoS
When the magnetic layer is formed by using the m alloy, Sm must be contained to some extent or more in order to exhibit a high coercive force. However, the saturation magnetization Ms decreases as the content of Sm increases, and when the content is 20 atomic% (hereinafter, simply referred to as%) or more, there is a problem that Ms decreases to 600 emu / cc or less.

The present invention has been made in view of the above problems, and an object of the present invention 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.

[0008]

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 a CrCu alloy containing atomic percentage of Cu: 0.5 to 15% and the balance of Cr.

[0009]

The nonmagnetic underlayer according to the present invention has a predetermined amount of C added to Cr.
It is formed of a CrCu alloy containing u. Cu
Does not form a solid solution in Cr, and easily segregates between Cr columnar crystals, which promotes grain refinement and separation. Therefore, 600 emu
In order to secure a high Ms of about / cc or more, even if the Sm content of the CoSm alloy forming the magnetic layer is lowered to about 20% or less, it has a high coercive force, and has a high Ms and a high coercive force. Can be combined. In this case, if the Cu content is less than 0.5 atom% (hereinafter, simply referred to as%), the coercive force improving effect of the magnetic layer becomes too small, while if it exceeds 15%, the crystal orientation of the Cr columnar crystal is destroyed. As a result, the in-plane orientation effect of the magnetic layer is deteriorated, so that the Cu content is 0.5 to
15%.

[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. The non-magnetic underlayer 2 formed on the substrate 1 is formed of a CrCu alloy as described above, and the in-plane crystal magnetic anisotropy of the CoSm alloy magnetic layer formed on the underlayer 2 is as described above. Improve. The layer thickness is usually about 500 to 2000Å.

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% or less in order to secure a high Ms of about 600 emu / cc or more. Note that 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
Alternatively, a non-magnetic intermediate layer made of Cr or the Cr alloy forming the underlayer may be alternately laminated. The layer thickness of the magnetic recording layer 3 (the layer thickness is a single layer of CoSm alloy, C is a layer of multiple layers).
The total thickness of the oSm alloy layer) is usually about 200 to 800Å.

On the magnetic recording layer 3, carbon, Si
The non-magnetic 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. (1) Using an RF ternary sputtering device, a Cr-3% Cu alloy underlayer of 1000 Å and various Sm on a glass substrate that was non-directionally textured by chemical corrosion.
The magnetic recording layer comprising a CoSm alloy magnetic layer with a content of 60
0Å, and a SiO ₂ protective layer was further laminated thereon to form 200Å. 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 m when the underlayer was formed.
200 W at Torr, 1 at 35 mTorr when forming magnetic layer
60 W, and 200 W at 15 mTorr when forming the protective layer. For comparison, a magnetic recording medium of a conventional example was formed under the same conditions as those of the example, except that the underlayer was formed by using Cr instead of the CrCu alloy. (2) Using the magnetic recording media of the obtained examples and conventional examples,
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, S
When the m content was reduced to 10%, the coercive force (Hc) was reduced to about 1500 Oe in the conventional example, but the coercive force is 2000 Oe or more in the examples. Further, it can be seen that the coercive force of the example having the CrCu alloy underlayer is improved by 500 to 600 Oe as compared with the conventional example regardless of the content of Sm. (3) Next, magnetic recording media of Examples having CrCu underlayers having various Cu contents were formed, and the influence of the Cu content on the coercive force was investigated. However, S of the CoSm alloy magnetic layer
The m content was 12%. Other film forming conditions and coercive force measuring conditions are the same as in (1) and (2). The result is shown in FIG. It can be seen from FIG. 3 that a high coercive force of about 2000 Oe or more is exhibited by including 0.5% or more of Cu in Cr.

[0015]

As described above, in the metal thin film type magnetic recording medium of the present invention, since the nonmagnetic underlayer is formed of the CrCu alloy having the specific composition, the miniaturization and separation of Cr crystal grains are promoted, The coercive force of the magnetic recording layer provided with the CoSm alloy magnetic layer can be remarkably improved. Therefore, the substrate is given a non-directional texture, and Sm is secured to secure high Ms.
Even if the content of is suppressed to a low level, a significant improvement in coercive force can be expected over the conventional one.

[Brief description of drawings]

FIG. 1 is a sectional view of essential parts of a metal thin film magnetic recording medium of the present invention.

FIG. 2 is a graph showing the relationship between the Sm content and the coercive force Hc in magnetic recording media of Examples and Conventional Examples having a CoSm magnetic layer.

FIG. 3 is a graph showing a relationship between a Cu content and a coercive force Hc in a magnetic recording medium of an example including a CrCu underlayer.

[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 atomic% and Cu: 0.5 to 15%.
A metal thin film magnetic recording medium, which essentially contains Cr and the balance is formed of a CrCu alloy composed of Cr.