JPH03228220A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain stable reproduction output by specifying the apparent anisotropic magnetic field in the film plane to a specified value or lower. CONSTITUTION:The magnetic recording medium consists of a substrate and an intrasurface magnetic anisotropy film comprising porous alumite. The apparent anisotropic magnetic field in the film plane is specified to <=100 Oe. The porous alumite has fine pores in the perpendicular direction to the film plane and each pore is completely separated from other pores by amorphous Al2P3. Thereby, the material having intrasurface magnetic anisotropy which fills these fine pores is completely magnetically separated in these pores and show complete isotropic magnetic characteristics in the film plane direction regardless to the conditions of filling or production device. Thereby, the reproduction output is stable and constant regardless of circumferential direction and radial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media. More specifically, the present invention relates to a magnetic recording medium with improved R/W characteristics.

[Prior Art] In order to improve the recording density of in-plane magnetic recording, the thickness of the in-plane magnetic anisotropic film provided on the substrate t has recently become thinner and thinner. Furthermore, in order to increase the amount of magnetization per unit volume, we gradually transitioned from a method in which acicular magnetic material such as iron oxide was coated on a substrate to a method in which a thin film of ferromagnetic material was physically deposited directly on the substrate. There is.

Currently, CoNi alloy in-plane magnetic anisotropic films formed by sputtering are being commercialized as thin film media instead of coating media. This CoNi alloy thin film medium is mainly targeted at rigid disks, and therefore requires constant R/W characteristics along the circumference of the circular disk.

In the current method, concentric scratches (texture) are formed on the disk substrate, and Cr is further provided as an underlying layer of the CoNi layer, thereby maintaining constant magnetic properties along the circumference.
In other words, stable R/W characteristics are obtained.

[Problem to be solved by the invention] However, due to equipment problems in the spatter process, completely constant magnetic properties cannot be obtained in the circumferential direction, and large anisotropy occurs in the circumferential and radial directions. It has become. Differences in magnetic characteristics in the circumferential direction result in fluctuations (modulation) in the reproduction output, which poses a problem in obtaining stable R/W characteristics.

Therefore, an object of the present invention is to provide a magnetic recording medium having an in-plane magnetic anisotropic film exhibiting stable R/W characteristics.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a magnetic recording medium having an in-plane magnetic anisotropic film made of porous alumite on a base, wherein Provided is a magnetic recording medium characterized in that an apparent anisotropic magnetic field is 1000e or less.

Preferably, this magnetic recording medium is a rigid disk.

[Function] As described above, the magnetic recording medium of the present invention has an in-plane magnetic anisotropy film using porous alumite.

Porous alumite has many fine pores in the direction perpendicular to the film surface.
(pore density: ~5×1010 pores/c12), and each micropore is completely separated by amorphous AJ203. Therefore, the materials exhibiting in-plane magnetic anisotropy filled in the micropores have a structure that is completely magnetically separated from each other in each micropore.

Therefore, it exhibits completely isotropic magnetic properties in the in-plane direction of the film, regardless of the filling condition 9 manufacturing apparatus.

Therefore, a constant and stable reproduction output can be obtained regardless of whether the reproduction output is in the circumferential direction or the radial direction.

The apparent −L in the film plane of the magnetic recording medium of the present invention
The anisotropic magnetic field of must be less than 1000e. In this specification, the term "apparent" refers to the anisotropy in the film plane obtained by rotating the sample within the magnetic field while applying a -like magnetic field (~15 kOe) in the in-plane direction of the film. From the magnetic energy (Ku), the following formula: Apparent anisotropic magnetic field in the film plane = 2 Ku / M
s (where MS is the saturation magnetization of the sample). When the apparent 1- anisotropic magnetic field (Hk) in the film plane exceeds 1000e, significant differences in magnetic properties occur depending on the direction and position of the medium, and as a result, stable reproduction output cannot be obtained. What is the lower limit of Hk (zero is the most ideal value)? In a state where Hk = 0, the film has completely isotropic magnetic properties within the film plane.

In order to control the apparent anisotropic magnetic field within the film plane to 1000e or less, each magnetic particle is completely separated with a non-magnetic material to prevent magnetic coupling (for example, an alumite fine This is done by replacing the magnetic particles or alumite in the pores with other non-magnetic material (eg, organic resin, CulAg, etc.).

The alumite layer can be formed directly on the substrate by anodizing the aluminum substrate, but it can also be formed by depositing aluminum or an aluminum alloy on a non-magnetic substrate by physical vapor deposition and then anodizing the deposited layer. I can do it. Examples of the physical vapor deposition method include a vacuum vapor deposition method, an ion blating method, a deposition method, a taring method, an ion beam deposition method, and a chemical vapor deposition method (CVD method).

Aluminum anodic oxidation methods are known. -For boat fishing, aluminum is anodized using direct current (DC). D
In C, increasing the current density increases the electric field strength and becomes more corrosive, resulting in more initiation points (pits). The pits generated at the initial stage of electrolysis are subsequently etched to form fine holes, resulting in porous alumite.

Examples of non-magnetic substrates used in the magnetic recording medium of the present invention include glass in addition to aluminum substrates.

Metal plates such as ceramic, anodized aluminum, and brass.

There is a Si single crystal plate whose surface is thermally oxidized.

[Example] Hereinafter, the present invention will be explained in detail with reference to examples.

Real IJ1 [A 3.5-inch size AJ1 substrate with a purity of 99.97% was cleaned and degreased in trichloroethane, and anodized at 18°C.
1 mol/J! of H2SO4 and 5g/λ of Aλ2 (S
The alumite layer was formed to a thickness of 0.45 μm by using a constant voltage of 17.5 V in an atmosphere containing O4)3. Next, the alumite was transferred to 1 wt% H3PO4 at 30°C, and 40 mA/d
The voltage between the electrodes (counter electrode: carbon) is 8V at a current density of m2.
It was re-formed.

Thereafter, the sample was immersed in the same bath to enlarge the micropore diameter of the alumite. After this treatment, chemical conversion was carried out in the same bath at a constant voltage of 8 µm to adjust and make the barrier layer uniform. At this time, the cell diameter of the alumite.

The bore diameters were 450 and 380, respectively.

Next, alumite was added, Co'': 0.2 mol/λ.

H3BO3: 0.2 mol/λ, glycerin = 2 mjl
/J2. Transferred to a plating bath containing NaPHz 02: 0.02 mol/λ, pH 4.0, AC3 at 20°C.
Using a power supply of 00Hz and 16Vpp, Co
P particles were filled to a thickness of 0.15 μm.

This sample was cut into 1 cm square pieces, an external magnetic field of 16 kOe was applied in the in-plane direction, and the anisotropy in the film plane was determined from the torque curve. The magnetic field Hk was 150e.

AJ with N1-P plating treatment with a thickness of 1.28-* as a non-magnetic substrate on the L cable! Using a substrate, 50% CoB□N12o
A film was formed by sputtering on a Cr base (5000 mm thick) with a thickness of 0 mm, and the in-plane anisotropy of the film was similarly determined.
The Hk was 8300e.

C of the sample obtained in Example 1 and Comparative Example 1.

In-plane magnetic properties (coercive force and squareness ratio) of Ni sputtered film
However, the first question is how the sample changes when the external magnetic field is always parallel to the film surface and the sample is rotated in that magnetic field.
As shown in the figure. In FIG. 1, the in-plane coercive force and the in-plane squareness ratio are normalized by the maximum value of each sample. For CO-P films (Aluminum), a constant in-plane coercive force and in-plane squareness ratio can be obtained even in the directions, whereas for a CoNi sputtered film, the in-plane coercive force varies from the maximum value to 19 depending on the angle. .7%, and the in-plane direction squareness ratio decreased by 9.8%.

From this fact, an in-plane magnetized film using alumite (in-plane direction coercive crab 7000e; in-plane direction squareness ratio: 0.84)
exhibits stable and constant characteristics within all samples, regardless of the location and direction of the sample, and is therefore considered to provide stable reproduction output.

[Effects of the invention] As explained above, by using an in-plane magnetic anisotropic film using alumite, certain stable magnetic properties and a low anisotropic magnetic field can be obtained in the plane of the medium. You can get playback output.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the orientation dependence of the in-plane magnetic properties of the Co--P metal alumite film in this example and the CoNi sputtered film in the comparative example.

Claims (3)

[Claims] (1) In a magnetic recording medium having an in-plane magnetic anisotropy film on a substrate, the apparent anisotropy magnetic field in the film plane is 100
A magnetic recording medium characterized in that the magnetic recording medium has a magnetic flux of 0e or less. (2) The magnetic recording medium according to claim 1, wherein the in-plane magnetic anisotropic film is an in-plane magnetic anisotropic film using porous alumite. (3) The magnetic recording medium according to claim 1 or 2, which is a rigid disk.