JPS6251024A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To simultaneously realize the decrease of noise and the improvement in the adhesive powder between layer constitutions by forming a metallic medium into the constitution in which an Ni-P alloy plating layer, surface-oxidized nonmagnetic metallic film and thin magnetic oxide film are successively coated thereon. CONSTITUTION:An aluminum alloy disk (substrate) 1 is subjected to a cleaning and zincate treatment and thereafter the Ni-P alloy film 2 is formed by using electroless Ni-P plating liquid. The film 2 is further subjected to lapping and polishing and after the oxide film on the Ni-P surface is removed by a reverse sputtering method in a vacuum vessel, a Cu film 3 which is a nonmagnetic metal is formed thereon with oxygen-free copper as a target in a gaseous Ar atmosphere and in succession, the disk is heated in a gaseous Ar atmosphere under 8% partial pressure of oxygen to form a film 4 of the dense copper oxide. An Fe3O4 film is further formed thereon by sputtering in using a target essentially consisting of Fe and thereafter a gamma-Fe2O3 film (magnetic film) 5 is formed by a heat treatment in the atm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium suitable for high-density recording in a thin film magnetic disk.

[Background of the invention]

Conventionally, magnetic disks have tended to have higher densities and thinner films, and as high-performance magnetic recording media, there are continuous thin film media that can easily be made into a 1 gram film. However, in recent years, oxide magnetic thin films mainly composed of γ-Fe2O3 have attracted attention, and like metal plating films, these can be made thin and have excellent magnetic properties, mechanical strength, and corrosion resistance. . The production of magnetic recording bodies using such oxide magnetic thin film media is as follows:
The process is roughly divided into a substrate forming process and a medium forming process.

In addition, the substrate used for forming the continuous thin film medium containing γ-Fe2O3 as a main component has (1) few defects, (ii)
) Do not interfere with the formation of the magnetic layer formed on the top; (iii
) No deterioration of characteristics due to heating process, (iv)5
It is desirable that the adhesion between the two be strong. Taking these points into consideration, conventional substrates include Ni-P, which reduces defects on disk substrates and obtains magnetic properties suitable for high-density recording.
A device in which a nonmagnetic nonmetallic film is provided on an alloy film is known (Japanese Unexamined Patent Publication No. 142735/1983).

However, in such conventional magnetic recording media, consideration has not been given to the reduction of noise due to the magnetization of Ni--P due to heating of the disk substrate, the adhesion between the metal film and the non-metal film, and the like.

[Purpose of the invention]

The purpose of the present invention is to improve such points that have not been taken into consideration in the past, to reduce defects in the disk substrate, and to reduce noise and improve the layer structure without hindering the growth of the magnetic layer formed on the disk substrate. An object of the present invention is to provide a magnetic recording medium having a structure that can simultaneously improve the adhesion between the two.

[Summary of the invention]

In order to achieve the above object, the magnetic recording medium of the present invention includes:
It is characterized by having a structure in which a metal medium is coated with a Ni--P alloy plating layer, a surface-oxidized nonmagnetic metal film, and an oxide magnetic thin film in this order.

[Embodiments of the invention]

An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of a magnetic recording medium showing one embodiment of the present invention.

In Fig. 1, 1 is an aluminum alloy disk, 2 is a Ni-P alloy film, 3 is a Cu film, 4 is an oxide layer on the surface of the intermediate film, and 5 is a γ-
It is a Fe2O3 film. The manufacturing process of this magnetic recording medium will be described below with reference to FIG.

First, a machined aluminum alloy disk (substrate) 1 is cleaned and treated with zincate, and then a Ni--P alloy film 2 with a thickness of about 20 μm is formed using an electroless Ni--P plating solution. This Ni-P alloy film 2 is further processed by lapping and polishing to make it flat and smooth and to have a film thickness of about 15 mm.
It was set as μm. The aluminum alloy substrate 1 on which the Ni-P alloy film 2 has been formed in this way is placed in a vacuum chamber, and after removing the oxide film on the Ni-P surface by reverse sputtering, oxygen-free copper is targeted. in an Ar gas atmosphere.

The Cu film 3, which is a non-magnetic metal, was deposited under the conditions of a sputtering pressure of 5 x 10-' Torr and an input power density of 6 W/cj.
The thicknesses were 0OA, 100OA, and 3000A. Subsequently, these substrates were heated at 200°C in an Ar gas atmosphere (7X 10'' Torr) with an oxygen partial pressure of 8%.
As a result of heating for a few minutes, a dense copper oxide film 4 of less than 100 octane was formed on the surface in each case. Furthermore, continue to
This substrate was placed in an Ar gas atmosphere with an oxygen partial pressure of 8% (7X 10
A Fe3O4 film with a thickness of approximately 0.15 μm was formed by reactive sputtering at an input power of 6 W/cII using a target containing Fe as the main component in an atmosphere of -3 Torr), followed by heat treatment in the air (290 ℃, 3Hr), γ
It was confirmed that the Fe2O3 film (magnetic film) 5 was formed normally.

As a result of examining the thin film magnetic recording medium thus formed, there were no defects with a diameter of 1 μm or more, and the growth of the magnetic layer was found to be normal. Also, when evaluating the magnetic properties, the saturation magnetic flux density Bs is 3000G (Gauss), and the coercive force He is 60
A result of 00e (Oersted) and S of 0.78 or more was obtained. As described above, the magnetic recording medium formed according to this example is excellent, and even in the beer test, no peeling occurred between the base film and the magnetic film.

Due to heat treatment, the underlying Ni-P film becomes magnetized to a maximum of about 100 Gauss, but it has been confirmed that a Cu film (intermediate film) 3 with a thickness of 100 OA or more can secure an S/N ratio of 36 dB or more. It was done.

As described above, in this embodiment, the defects in the base material can be compensated for by using the Ni--P plating film to reduce defects, which is necessary for a substrate suitable for high-density recording. Furthermore, a dense oxide film can be provided in the intermediate layer so as not to hinder the growth of the upper oxide magnetic layer. Furthermore, the base film (Ni-P alloy film) 2 and the magnetic film (r
It also helps improve the adhesion of the Fe2O3 film)5. Further, noise can be reduced by making the thickness of the intermediate layer 100 OA or more.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reduce defects in the disk substrate, and at the same time reduce noise and improve adhesion between layers without hindering the growth of the magnetic layer formed on the disk substrate. It is possible to realize a magnetic recording medium having a configuration that allows

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magnetic recording medium showing an embodiment of the present invention. 1 Ni-aluminum alloy disk, 2: Ni-P alloy film (base film),
3: Cu film (intermediate film), 4: oxide layer on the surface of the intermediate film,
5: y-Fe2O3 film (magnetic film). ,′, ,＼
4(...

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a metal substrate is coated with a Ni-P alloy plating layer, a surface-oxidized nonmagnetic metal film, and an oxide magnetic thin film in this order.