JPS6199924A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the noise in the stage of high density recording and to obtain a vertical magnetic recording having excellent S/N by forming a vertically magnetizable film consisting of Co-O or Co-Ni-O as a magnetic recording layer and specifying the CoO content of the surface layer part. CONSTITUTION:The vertically magnetizable film consisting of Co-O or Co-Ni-O is formed as the magnetic recording layer 6 and the CoO content of the surface layer part is specified at <=10%. The S/N can be improved in the stage of high density recording and reproducing by using the vertically magnetizable film consisting of Co-O or Co-Ni-O as the magnetic recording layer. The component generated by the magnetic unevenness arising from the varying degree of the interaction of the ferromagnetism and antiferromagnetism of Co and CoO among the sources for generating noise is substantially of no problem in practicable use when the ratio of CoO decreases to <=10% but the noise increases by 2-3dB at <=0.4mum recording wavelength if the ratio exceeds 10% and therefore the ratio of the CoO is preferably decreased to <=10%.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium suitable for high-density magnetic recording.

Conventional configurations and their problems In recent years, with the increasing demand for higher density magnetic recording, perpendicular recording systems have been proposed that have features not found in conventional longitudinal recording.
It is being considered.

Perpendicular recording uses a magnetic recording medium that has an axis of easy magnetization perpendicular to the running direction of the magnetic recording medium such as a tape or disk, that is, in the thickness direction of the magnetic recording layer, and magnetizes the magnetic recording medium in the thickness direction. Moreover, it is constructed so that the magnetization remains in this direction, and by doing so, the self-demagnetizing field can be made smaller as the wavelength becomes shorter, and as a result, it is attracting attention as it makes it possible to increase the density. be.

As an example of the configuration is shown in FIG. 1, a magnetic disk or magnetic tape 1 is made by laminating a soft magnetic layer 3 and a perpendicularly magnetized film 4 such as Go-Or on a non-magnetic substrate 2 such as a polymer film. used.

Looking at this media configuration from the perspective of mass production, Co-Or
From a performance standpoint, perpendicular magnetization films are best obtained by sputtering, which has an extremely low film formation rate.Those that can be obtained by electron beam evaporation, which has excellent mass productivity, have a high vapor pressure of Co and Cr. Because of the difference, the deposition control becomes complicated, and the performance is also not satisfactory, and in particular, the need to raise the substrate temperature to a high temperature to obtain a high coercive force number is an obstacle to practical application. .

Recently, GO-O,G, which has been used in longitudinal recording
o - Go - which can obtain high coercive force without raising the substrate temperature that much using a manufacturing method similar to that of the obliquely deposited Ni-0 film.
'O, Co-Ni-0 perpendicular magnetization films are attracting attention instead of Co-Cr.

However, it is relatively easy to obtain a perpendicularly magnetizable film using a Go-0, Co-N knee film because of the production technology for magnetic tape for longitudinal recording, as mentioned above. In terms of performance, it is insufficient compared to the Go-Or sputtered film.

In other words, the signal-to-noise (S/N) ratio is far from the value required for practical use, and in particular, noise during high-density recording requires improvement.

Purpose of the Invention The present invention was made in view of the above circumstances.
□ The aim is to improve the noise during high-density recording of a magnetic recording medium using a -Ni -0 perpendicular magnetization film as a magnetic recording layer, and to realize perpendicular magnetic recording with an excellent S/N ratio.

The target is

Structure of the Invention The magnetic recording medium of the present invention is Go-0 or Go-Ni-
The magnetic recording layer is a 0-based perpendicular magnetization film, the CoO content in the surface layer is 10% or less, and the S/N is good during high-density recording.

Description of examples The present invention will be described below with reference to the drawings.

FIG. 2 is an enlarged sectional view of a main part of the magnetic recording medium of the present invention.

In FIG. 2, numeral 5 indicates microcrystalline particles constituting the perpendicularly magnetized film, and the thickness of the thin film is t. Then, the surface layer here is 0.2
It refers to the part 6 on the front side up to . 7 is a substrate or a soft magnetic layer.

The critical significance of the volume ratio of CoO contained in the surface layer being 10% or less comes from the regulation of the noise level, as will be described later.
This is confirmed in a range of 1 μm.

In order to keep the volume ratio of CoO in this range, (lio(
OH)2. The surface protective layer may be mainly composed of Ga2O3.

In particular, a medium composed of Ga5O4 has the advantage of improved corrosion resistance.

Among the sources of noise, the component that occurs due to magnetic unevenness due to the magnitude of the ferromagnetic 9 antiferromagnetic interaction between co and Go O is practically acceptable when CoO is less than 10%. However, if it becomes 10% or more, the recording wavelength increases by 2 to 3 dB at 0.4 μm or less, so 10%
It is preferable to suppress CoO as follows.

To manufacture the magnetic recording medium of the present invention, for example, while winding a polymer substrate along a cylindrical can, the incident angle component C is set such that the incident angle is approximately perpendicular.

or Go-0 obtained by directing Co-Ni vapor and introducing oxygen or ozone into the vacuum system, or Go-
A Ni -0 perpendicular magnetization film was heated at 40°C to 80°C in an oxygen atmosphere.
An example is a method of aging at C for a long time, for example, 64 to 120 hours.

An example will be described in more detail below.

(Example) 60"/Cd 11μm thick polyamide substrate.

Oxygen glow discharge treatment was performed at 0.3 Torr, and a permalloy thin film (magnetic permeability 760) with a thickness of 0.39 μm was formed by high-frequency sputtering, and on top of that, CoO perpendicular magnetization of 0 and 15 μm with various CoO contents was formed. form a film, S
/N were compared relative to each other with a vertical head arranged on one side.

The conditions for forming the perpendicularly magnetized film are: substrate temperature: O'C to 34°C;
Oxygen partial pressure: I Xl 0”Torr~4×10-’T
orr, Go deposition rate: 14o/sea ~1
900 people/sea, the incident angle was selected within 6 degrees, and the post-processing to change the CoO content was performed at 35°C and 88% RH.
aging treatment for 40 to 120 hours; 13.
156M) lz e W/cd ~44 W/c4,
Either of two types of high frequency glow discharge treatments were used: o2o, oe~o, and 4 Torr. The COO content was determined by X-ray electron spectroscopy.

The recording bit size is 0.2 μm×12 μm.

For comparison, a perpendicularly magnetized film was made of 0.15 μm Co Cr [perpendicular coercive force goo (Oe), saturation magnetic flux density 40
00(G):] The S/N of the tape obtained by configuring is -o,
It was 4 (dB).

From this data and the results in the table above, the magnetic recording medium of the present invention has an extremely good S/N ratio in high-density recording and reproduction.

In addition, even if a medium whose surface protective layer is formed mainly of CO3O4 is stored in an environment of 40°C, 90% RH, 60'CB, 5% RH for two months, there is almost no change in the total magnetic flux before and after. points are also advantageous.

It goes without saying that the present invention exhibits exactly the same effect not only on magnetic tapes but also on magnetic disks.
It has been confirmed that other materials have similar effects.

Effects of the Invention As described above, the magnetic recording medium of the present invention has a Co
Go-0 or Co-N with an O content of 10% or less
By using i-0 system perpendicular magnetization film as the magnetic recording layer, S/N can be improved.
can be improved during high-density recording and reproduction, and its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a magnetic recording medium for perpendicular recording, and FIG. 2 is a partially enlarged sectional view of the magnetic recording medium of the present invention. 5... Microcrystal constituting the perpendicular magnetization film, 6...
...surface part. Agent's name: Attorney Toshi Nakao Haga 1 person 1st
Figure θ,? t.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a Co-O or Co-Ni-O based perpendicularly magnetized film as a magnetic recording layer, the CoO content of the surface layer being 10% or less.