JP2515756B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

The present invention relates to a method for manufacturing a recording medium used for magnetic recording, particularly a recording medium suitable for high density recording.

[Conventional technology]

As a recording medium used for magnetic recording, a magnetic powder coated on a substrate has been conventionally used, but recently, as a recording medium capable of high density recording, a Co-Ni sputtering film or a Co-P film is used.
A medium using a so-called continuous film such as a plated film is being put to practical use.

These continuous film media are described, for example, in I.E.E.Transaction on Magnetics, M.A. 18 (1982), pages 1215 to 1220 (IEEE, Trans, Mag.
netics MAG18 (1982) pp1215-1220) and 1985 IEICE General Conference Conference Proceedings 1-227.

[Problems to be solved by the invention]

However, the recording medium using the continuous magnetic film has a drawback that noise is large when high density recording is performed.

The present invention provides a method of manufacturing a magnetic recording medium that can achieve high-density recording with less noise by using a continuous magnetic film.

[Means for solving problems]

The present inventors have proposed, as a recording medium with less noise and capable of achieving a high recording density, a magnetic film in which the easy axis of magnetization is oriented in the film plane perpendicular to the film plane. It has been found that those provided with are suitable.

As a method for producing a magnetic film having a different easy axis of magnetization, a method using two kinds of magnetic films made of different materials, or a DC film when a magnetic film of the same quality is used by the sputtering method is used.
There is a method of changing the bias voltage.

When a magnetic film in which the easy axis of magnetization is oriented in the direction perpendicular to the film surface is used, C, Ge, S
It is desirable to provide a thin film made of a material containing at least one element of i.

[Action]

It is considered that the noise when the continuous magnetic film is used is caused by the sawtooth magnetic domains as shown in FIG. This saw-tooth magnetic domain is, for example, the I-E-E-Transaction of Magnetics MG (IEEE).
Trans.Magnetics MAG) 10 (1974) Page 674 to 677
Page. The double-headed arrow in FIG. 2 indicates the direction of magnetization. It is considered that the sawtooth magnetic domains are generated to reduce the generation of magnetic poles at the boundaries between the magnetic domains facing each other.

On the other hand, the magnetic domain structure according to the present invention is as shown in FIG. 1, but since the generation of magnetic poles is reduced by the perpendicular magnetic layer provided in the lower layer, the sawtooth magnetic domain hardly appears.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 On an Al disc having an outer diameter of 130 mmφ, an inner diameter of 40 mmφ and a thickness of 1.9 mm,
A substrate with a NiP film with a thickness of 15 μm was used as a substrate, a C (carbon) film with a thickness of 0.005 μm (50 Å) was provided on this substrate, and a Co ₈₀ Cr ₂₀ film with a thickness of 0.03 μm was subsequently provided. .
Next, after a Co ₇₀ Ni ₃₀ film having a film thickness of 0.03 μm was provided, a C film having a film thickness of 0.02 μm was provided thereon. Each thin film was prepared by a magnetron sputtering method with a DC bias voltage of zero.

All target diameters for making each thin film are 200mm
φ, the Ar pressure at the time of sputtering was 5 mmTorr, and the sputtering power was 1 kW.

The recording medium manufactured as described above and the gap length of 0.2
Using a MnZn ferrite head having a track width of 100 μm, a track width of 100 μm, and a winding number of 12 turns, a recording / reproducing experiment was performed at a head flying height of 0.20 μm and a relative speed between head media of 20 m / sec.

As a result, the playback output at a recording frequency of 0.1 MHz is 2.25.
The recording density D _{50, which} is mVpp and gives a reproduction output that is 1/2 of the reproduction output at 0.1 MHz, was 28 kfci. The noise level at a recording frequency of 10 MHz was 3.6 μVrms.

A C film having a thickness of 0.005 μm was provided on the same substrate as that used in this example, and a C film having a film thickness of 0.03 μm was continuously formed.
o From the magnetic torque curve of the sample with the ₈₀ Cr ₂₀ film, this Co
It was found that the easy axis of the ₈₀ Cr ₂₀ film was oriented in the direction perpendicular to the film surface. Further, by using the magnetization curve of this Co ₈₀ Cr ₂₀ film, from the magnetization curve of the Co ₇₀ Ni ₃₀ / Co ₈₀ Cr ₂₀ film of this example, Co ₇₀ Ni ₃₀
When the magnetization curve of the film was obtained, the squareness ratio in the film plane was 0.90,
Coercive force 750 Oe, squareness ratio perpendicular to film surface is 0.10, coercive force is 1
It was 10 Oe, and it was found that the easy axis of magnetization was in the film plane.

Example 2 An Al disk having the same shape as that of Example 1 provided with a NiP film having a thickness of 15 μm was used as a substrate, and a thickness of 0.00
A 5 μm C film was provided. Next, Co ₈₀ Cr with a film thickness of 0.03 μm
₂₀ films were prepared by the magnetron sputtering method while continuously changing the DC bias voltage from 0 to -200V.
With the bias voltage fixed at -200 V, the film thickness of 0.03 μm
A Co ₈₀ Cr ₂₀ film was prepared.

The recording / reproducing characteristics of the recording medium thus manufactured are
Using the same magnetic head as in Example 1, the measurement was performed under the same conditions as in Example 1. As a result, the reproduction output at a recording frequency of 0.1 MHz was 2.20 mVpp and D ₅₀ was 29 kfci. The noise level at a recording frequency of 10 MHz is 3.2 μVrms.
It was.

In addition, in the above process, the DC bias voltage was continuously changed from 0 to −100 V, and the Co film with a thickness of 0.015 μm was manufactured.
_The axis of easy magnetization of the ₈₀ Cr ₂₀ film is oriented in the direction perpendicular to the film surface, and DC
Co ₈₀ with a film thickness of 0.03μm manufactured with a fixed bias voltage of -200V
The easy axis of magnetization of the Cr ₂₀ film lies in the film plane.

Comparative Example A 15 μm thick NiP film provided on an Al disk having the same shape as that of the example was used as a substrate.
After providing the Cr film of μm, a Co ₇₀ Ni ₃₀ film of 0.06 μm was provided, and further a C film of 0.02 μm was provided thereon. Each thin film was prepared by the magnetron sputtering method under the condition that no DC bias voltage was applied. The target diameter and the sputtering conditions are the same as in the first embodiment.

When a recording / reproducing experiment was conducted under the same head and the same measurement conditions as in Example 1, the reproducing output at a recording frequency of 0.1 MHz was 2.24 mVpp, D ₅₀ was 22 kfci, and noise was 17.8 μVrm.
s

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain a recording medium having excellent recording density characteristics and less noise than conventional recording media.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a recording state in a magnetic film according to the present invention, and FIG. 2 is a schematic diagram of magnetization in a recording state in a conventional continuous magnetic film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Sadao Hishiyama, 1-280 Higashi Koigakubo, Kokubunji City, Central Research Laboratory, Hitachi, Ltd. (72) Kenji Furusawa, 292 Yoshida-cho, Totsuka-ku, Yokohama City Hitachi, Ltd. In-house (72) Inventor Katsuo Abe 292 Yoshida-cho, Totsuka-ku, Yokohama Inside Hitachi Institute of Industrial Science (72) Inventor Makoto Sano 2880 Kozu, Odawara-shi Hitachi Ltd. Odawara Factory (72) Inventor Yo Kitazaki Shishi Odawara City, Kozu 2880 In Hitachi Co., Ltd.Odawara Plant (72) Inventor Takaaki Shirakura 2880 Kunizu, Odawara City Hitachi Co., Ltd.Odawara Plant (72) Inventor Sakae Ota 2880, Kozu, Hitachi Odawara Plant (56) References JP 60- 261026 (JP, A) JP-A-60-25027 (JP, A)

Claims (1)

(57) [Claims] 1. A method of manufacturing a magnetic recording medium, comprising: providing a magnetic film having an easy axis of magnetization oriented in a direction perpendicular to a film surface on a substrate, and then providing a magnetic film having an easy axis of magnetization oriented in the film surface. 2 made of the same material but with different easy magnetization axis directions
When providing different types of magnetic films, the sputter method is used together,
A method of manufacturing a magnetic recording medium, characterized in that a direction of an easy axis of magnetization is changed by changing a DC bias voltage.