JPH03241526A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To execute magnetic recording at a high density by applying a concentrical texture on the surface of an NiP alloy film formed on a nonmagnetic substrate and forming a magnetic layer via a nonmagnetic underlying layer on the substrate from which the surface oxide layer of the alloy film is removed. CONSTITUTION:The NiP alloy film 2 is formed in order to maintain the mechanical strength of a magnetic disk on the surface of the nonmagnetic substrate 1 consisting of an AlMg alloy. Since the surface of the film 2 is rugged, the surface is polished and further the texture is applied concentrically with the substrate on this surface to produce the disk substrate. Since the surface of the film 2 is coated with the surface oxide layer at the point of this time, the oxide film is removed and thereafter the Cr underlying layer 3, a magnetic film 4 and a protective film 5 are formed in order to improve the magnetic characteristics of the magnetic film. Such magnetic anistropy that the texture direction is a difficult axis is induced in spite of the concentrical texturing and, therefore, the squarness ratio of the texture direction is small and the high-density magnetic recording is executed with small medium noise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium on which an underlayer is formed that is effective in improving electromagnetic conversion characteristics and durability.

Conventional technology In recent years, magnetic disk devices have become capable of higher recording densities.

There is an increasing demand for shorter access times and faster transfer rates. Along with this, magnetic recording media are changing from oxide coated media to metal thin film media with high coercive force and high residual magnetic flux density produced by sputtering or plating methods.

In order to achieve high-density recording, it is important to increase signal output and reduce media modulation noise associated with bit shifts and the like.

In general, the modulation noise of a medium depends on the squareness ratio of the magnetization-magnetic field (B-H) curve due to the relationship of demagnetization, and as the squareness ratio increases, the modulation noise increases, and as the squareness ratio decreases, the modulation noise increases. is also trending lower.

A magnetic recording medium with a small squareness ratio and low modulation noise is manufactured using a sputtering method using high gas pressure during film formation, and a magnetic recording medium with a radially textured disk substrate plated with NiP alloy. There is a medium.

Problems to be Solved by the Invention However, in the former magnetic recording medium, since the gas pressure must be increased during film formation, the gaps between particles in the film are large and the corrosion resistance is poor in a high temperature and high humidity environment.

Furthermore, in the latter magnetic recording medium, contact start/stop characteristics (hereinafter abbreviated as C3S characteristics) and head flying characteristics are inferior due to unevenness in the lateral direction of the magnetic head. Furthermore, it is difficult to provide a radially uniform texture.

Therefore, even if the above-mentioned magnetic recording media have a small squareness ratio and low modulation noise of the medium, there are problems with environmental resistance, C8S characteristics, head flying characteristics, etc. Records cannot be achieved.

An object of the present invention is to solve the above problems and provide a magnetic recording medium with good noise characteristics and durability.

Means for Solving the Problems In order to achieve the above object, the present invention removes the surface oxidation layer of a disk substrate formed by adding a concentric texture to the surface of an N i P alloy film formed on a non-magnetic substrate, A magnetic layer is formed through a nonmagnetic underlayer without oxidizing the substrate surface.

Although the magnetic recording medium of the present invention has a concentric texture, by removing the surface oxidation layer on the disk substrate, the magnetic anisotropy in which the difficult axis is parallel to the texture can be improved. As a result, the squareness ratio becomes smaller.

Embodiment FIG. 1 is a sectional view showing a magnetic recording medium according to an embodiment of the present invention. In order to maintain the mechanical strength of the magnetic disk on the surface of the lightweight, non-magnetic AIMq alloy substrate 1, a NiP alloy film (P concentration: 11 wt%) 2 is formed to a thickness of 15 μm by electroless plating. Since the surface of the N i P alloy film 2 is uneven, it is polished to a mirror surface using Ae203 abrasive grains.

Furthermore, using 42o3 wrapping tape, a texture concentric with the Deinuk substrate was applied to the surface with an average surface roughness of R.
A disk substrate is manufactured by attaching the number of people so that a=60 people. After cleaning and drying, this disk substrate is set in a sputtering device. At this point, the surface of the Dainuk substrate, that is, the surface of the textured N t P alloy film, is
Covered with a surface oxide layer. Start vacuuming the sputtering equipment, and when the vacuum level reaches 10' and Torr level, increase the vacuum to 200
W, reverse sputtering of type 30 is performed to remove N i P on the substrate surface.
Remove the surface oxide layer of the alloy film. Thereafter, by continuous DC magnetron sputtering method, Ar gas pressure was 1 mTo.
3000 people successively formed the Cr base film 3 to improve the magnetic properties of the magnetic film using r r, 600 people formed the CoNiCr magnetic film 4, and 200 people successively formed the carbon C surface protective film 5. An example magnetic recording medium is manufactured.

FIG. 2 shows a cross-sectional view of the magnetic recording medium of Comparative Example A. On the surface of the same disk substrate as in the example, without removing the surface oxide layer 6 of the NLP alloy film, the magnetic properties of the magnetic film were improved using Ar gas pressure as high as 30 mTorr by DC magnetron sputtering. 3,000 people successively formed the Cr base film 3, 600 people formed the CoNiCr magnetic film 4, and 200 people formed the carbon C surface protection film 6.
A magnetic recording medium of Comparative Example A was produced.

In addition, with the structure shown in FIG. 2, the same disk substrate as in the example was coated with a 5.
At an Ar gas pressure of 1 mTozr, 3,000 CoNiCr and CoNiCr underlayers were formed to improve the magnetic properties of the magnetic film.
600 people for magnetic film 4, 20 people for carbon C surface protection film 5
A magnetic recording medium of Comparative Example B was produced by continuously forming 0 persons.

The measurement results of the magnetostatic properties of the magnetic recording media of Examples, Comparative Examples A and B are shown in Table 1 below, and the dependence of the media modulation noise on the recording density is shown in FIG.

The squareness ratio of the example button and comparative example A is much smaller than that of comparative example B. The medium modulation noise in Examples and Comparative Example A is also much lower than in Comparative Example B.

In particular, the medium modulation noise in Example and Comparative Example A is low in areas with high recording density, but in Comparative Example B, the medium modulation noise increases rapidly in areas with high recording density9. The difference becomes noticeable.

In Comparative Example B, the squareness ratio shows a large value of 0.90, but this is because the texture induces magnetic anisotropy such that the easy axis is the parallel direction. The difference between the example and comparative example B is that the N on the surface of the disk substrate
This is due only to the presence or absence of the surface oxidation layer of the iP alloy film. In other words, even though the texture is concentric in Example B, the squareness ratio is very small compared to Comparative Example B because the surface oxide layer of the NLP alloy film on the surface of the Dainuk substrate was removed. Magnetic anisotropy with the easy axis parallel to the texture direction is not induced, but magnetic anisotropy with the easy axis perpendicular to the texture direction is induced, resulting in a smaller squareness ratio and smaller media modulation noise. It has become.

Finally, we investigated corrosion resistance, which is an important issue when incorporating magnetic recording media into actual drives.

The magnetic recording media of Example A and Comparative Example A were prepared at a concentration of 1 mol.
Saturation magnetic flux density B after being immersed in /1 saline solution for 6 hours and saturation magnetic flux density B before being immersed in saline solution. The ratio B/Bo is shown in Table 2 below.

Table 2 B02 Saturation magnetic flux density B before immersion in salt water: Saturation magnetic flux density after immersion in salt water In the example, the ratio of saturation magnetic flux density B/B0 is 0.98 and hardly changes before and after immersion in salt water. do not. On the other hand, in Comparative Example A, the saturation magnetic flux density ratio B/Bo decreases to 0.86 by immersing it in the saline solution, but this is because the magnetic film is corroded by the saline solution and becomes non-magnetic. That is, although Comparative Example A has poor corrosion resistance, Examples have excellent corrosion resistance.

In this example, the non-magnetic underlayer is made of Or and the magnetic layer is made of Co.
Although NiCr was used, the nonmagnetic underlayer may be made of a metal other than Cr such as Mo or W, and the magnetic layer may be made of CoNiCr.
In addition, Co Ni, CoP t, CoCr
Metals such as

Effects of the Invention As is clear from the above examples, the present invention provides a concentric texture on the surface of the NLP alloy film formed on a nonmagnetic substrate, and removes the surface oxide layer of the NLP alloy film. A magnetic layer is formed on a Deinuk substrate via a non-magnetic underlayer without oxidizing the surface, and even though the texture is circular, the direction of the texture is a difficult axis. Since such magnetic anisotropy is induced, the squareness ratio in the texture direction is small, and therefore, medium modulation noise is also small, allowing high-density magnetic recording. Dimension A
Since the film can be formed at a low r gas pressure, the formed film is a dense film and is a magnetic recording medium with excellent corrosion resistance. Furthermore, since the texture is concentric, there is no problem with C3S characteristics or head flying characteristics. Therefore, high-density magnetic recording can be achieved by incorporating the magnetic recording medium of the present invention into an actual drive.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a magnetic recording medium according to an embodiment of the present invention, and FIG.
The figure is a cross-sectional view of the magnetic recording media of Comparative Example AI- and Comparative Example B, and FIG. 3 is a recording density dependence characteristic diagram of medium modulation noise. 1...Nonmagnetic substrate, 2...NiP
Alloy film, 3...Cr base film (non-magnetic base layer),
4...CoNiCr magnetic film (magnetic layer).

Claims (1)

[Claims] A magnetic recording medium in which the surface of a NiP alloy film formed on a non-magnetic substrate is provided with a concentric texture, and a magnetic layer is formed on a disk substrate with a surface oxidation layer of the alloy film removed via a non-magnetic underlayer.