JPS6339128A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the productivity of a magnetic disk by forming a thin chromium alloy film contg. iron at a specific ratio as an underlying layer for a thin magnetic film. CONSTITUTION:This recording medium is formed by forming the thin chromium alloy film contg. 3.0-30.0wt% iron as the underlying layer for the thin magnetic film. The toughness of a target material can be increased by using a Cr-Fe alloy target material formed by adding the iron to the chromium. The target is not cracked even if the sputtering speed is increased; therefore, the productivity of the magnetic disk is considerably improved. The iron has the same body- centered cubic lattice as the body-centered cubic lattice of the chromium at an ordinary temp. and the lattice constant thereof is approximately the same. The epitaxy to parallel to the C-axis of cobalt with the substrate plane is no longer hindered at the time of sputtering a cobalt material on the subsurface consisting of a chromium-iron alloy. The magnetic characteristics approximately equal to the magnetic characteristics obtainable when the cobalt material is sputtered on pure chromium are thus obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium, and in particular, by using a chromium-iron alloy thin film as the underlayer of a cobalt or cobalt alloy magnetic thin film, the underlayer thin film can be formed by sputtering. This improves productivity when applying on aluminum substrates.

[Conventional technology]

2. Description of the Related Art Magnetic recording media used in recording devices for electronic computers generally include a substrate made of an aluminum alloy whose surface is coated with a magnetic material. Such magnetic recording media are manufactured by processing a substrate to a predetermined thickness, mirror-polishing the surface, and then polishing the surface with γ-FhOs.

It is manufactured by applying a mixture of cobalt-doped magnetic powder such as γ-Fe, O, etc. and resin powder, and then heat-treating it to form a magnetic film.

In recent years, magnetic recording media have been required to have larger capacities and higher densities, and as a result, the magnetized area per bit has become smaller and smaller, and magnetic films are also desired to be thinner. .

For this reason, after processing the substrate to a predetermined thickness, the surface is cleaned and then a hard non-magnetic metal such as a Ni-P alloy is coated as a base treatment (primary base layer) for coating with magnetic material. Magnetic recording media have been proposed that are electrolytically peeled or anodized, and then coated with a magnetic thin film by chemical plating or physical plating such as vapor deposition or sputtering. A method of directly coating a substrate with a magnetic thin film has also been proposed.

The internal sputtering method for coating the magnetic thin film has been attracting attention recently because it has advantages such as high reliability and the ability to produce alloy thin films.

Cobalt and cobalt alloys are excellent materials for magnetic films, but in order to improve the magnetic properties in the horizontal direction, that is, in the magnetic plane, oblique evaporation is performed, and the underlayer (secondary layer) of the cobalt-based magnetic film is used. A pure chromium thin film is applied as an underlayer (base layer). However, in the production of magnetic recording media such as hard disks, the oblique deposition method requires too complicated equipment and is difficult to operate, so the latter method is exclusively used. This method improves magnetic properties because the (110) plane of a chromium crystal (body-centered cubic lattice) deposited or sputtered on the substrate grows parallel to the substrate, and on this plane cobalt or cobalt as a magnetic material is grown. (By evaporating or sputtering a metal alloy, it is possible to grow epitaxially so that the C axis, which is the axis of easy magnetization of cobalt (close-packed hexagonal lattice), is parallel to the substrate surface. J, DAVAL
,D,RANDET(IEEEETRANSACTIO
NS ON MACNET C3, VOL, MAG
-6,,No,lt.

1970) and others. They form Co-Ni-Cr thin films by vapor deposition, but recently they have used sputtering equipment to form Co-Ni-Cr alloy films on magnetic films, improving magnetic properties and corrosion resistance. By reducing the thickness of pure chromium as the secondary underlayer,
Attempts have been made to reduce the amount of chromium target used (Yamada, Tani, Ishikawa, Ota, Nakamura, Ito, 1985 IEICE General National Conference 1-199). In forming such a magnetic alloy thin film, it is difficult to apply a vapor deposition method because of the difference in vapor pressure of the added elements, and a sputtering method is generally used.

[Problem that the invention seeks to solve]

In the magnetic recording medium in which pure chromium is sputtered as the secondary underlayer described above, there has conventionally been a problem in terms of productivity when forming a pure chromium thin film on an aluminum substrate. In other words, if the power is increased too much during sputtering, the temperature of the target surface will rise, causing thermal stress due to the difference in thermal expansion from the water-cooled back surface of the target, but since pure chromium is brittle, this thermal stress can cause the target to crack. It was not possible to increase the sputtering speed. As a result, productivity has not increased and it has been difficult to reduce the price of magnetic recording media.

Furthermore, since pure chromium has a high melting point and is brittle, it is difficult to form a target by melting, casting, or rolling, and since it is produced by a powder sintering method, the target itself is expensive.

[Means for Solving Problem C] The present invention was obtained as a result of intensive research to solve these problems, and is a magnetic recording medium having a cobalt or cobalt alloy magnetic thin film on an aluminum substrate. 3.0 to 30.0 w of iron as the underlayer of the magnetic thin film
This magnetic recording medium is characterized by being coated with a chromium alloy thin film containing t%.

[For production]

The present inventor searched for various additive elements that could increase the toughness of the chromium target material without significantly changing the crystal structure of chromium, and found that iron was the best. In other words, by using a Cr-Fe alloy target material in which iron is added to chromium, the toughness of the target material can be increased, and even if the sputtering speed is increased, the target will not crack, thus greatly increasing the productivity of magnetic disks. can be improved. In addition, iron has the same body-centered cubic lattice as chromium at room temperature and has almost the same lattice constant, so when sputtering a cobalt-based material onto a chromium-iron alloy substrate, the C axis of cobalt is parallel to the substrate surface. Thus, epitaxial growth is not inhibited, and magnetic properties almost equivalent to those obtained by sputtering a cobalt-based material on pure chromium can be obtained. Furthermore, 0r- which added iron to chromium
By using Fe alloy, the toughness of the target material increases and the melting point decreases, so the target material can be easily manufactured by melting and casting, and the price of the target itself can be reduced.

In the present invention, the amount of iron added to the Orr-Fe alloy target material is 0 to 30. The reason why it was limited to 0wt% was 3. If it is less than 0 wt%, the increase in toughness is insufficient and the sputtering rate cannot be increased, and if it is less than 30 wt%
This is because if it exceeds 100%, the chromium alloy of the underlayer becomes magnetic, causing noise and the like.

The magnetic recording medium of the present invention is produced by processing an aluminum substrate to a predetermined thickness, mirror-finishing the surface, and then electrolessly plating a hard non-magnetic metal, such as a Ni-P alloy, as a primary underlayer. Alternatively, anodization treatment may be applied, followed by 0.05-0.4 pm of chromium as a secondary underlayer.
It can be obtained by sputtering an iron ('3.0 to 30.0 wt%) alloy thin film and then applying a cobalt or cobalt alloy magnetic thin film of about 0.05 to 0.2 μm by sputtering, plating, etc. It is also possible to sputter a chromium-iron alloy as a second underlayer directly onto a mirror-finished aluminum substrate without applying a first underlayer.

〔Example〕

Examples of the present invention will be described below.

As shown in Table 1, iron is added to chromium in an amount of 0 to 35 wt%, and after high-frequency melting in Ar gas at 0.5 atmospheres, it is cast into an iron mold with a thickness of 15+ nm, a width of 220 mm, and a length of 220 m+.
An ingot was obtained. This ingot was machined into a disk with a thickness of 6 fins and a diameter of 200 mm, which was set in a magnetron sputtering apparatus shown in FIG. 1 and used as a target. In FIG. 1, 1 is a target, 2 is an aluminum substrate, 2 is a copper plate, and Ia and IIb are magnets. After mirror-polishing an aluminum substrate 2 with a diameter of 525'', Ni-P electroless plating was applied as a second base layer, and sputtering was performed to a thickness of 01 μm using the chromium-iron alloy target 1 as a second base layer. .

Table 1 shows the results of measuring the highest sputtering speed at which sputtering could be performed without cracking the target 1. Then, a CO-30 at% Ni-7,5 at% Cr alloy was deposited on the chromium alloy base layer.
1 μm sputtering, and additionally 0.0 µm of C as a protective film.
A magnetic recording medium of the present invention was obtained by sputtering to a thickness of 3 μm. 2.5 K of the outermost track of the magnetic recording medium
The results of measuring the reproduction output at Hz are also listed in Table 1.

Table 1 1 Composition (wt%) Maximum sputtering Reproduction output 1” Fe cr Speed (μmV/min) (mV) 1 3#
0 remaining 0.21 2.70 pieces
2 3. Or O, 252, 71□ 1 shot/310. Oz O,292,69 Ming 1
+ 13.0' p O, 312,
68 cases 5 20. Oz O, 332
,66625,0z O,372,61
7 U0.0 1 0.4
U 2. U6 ratio s
ol remaining 0.082.71 comparison 9
2. Oz O, 092, 70 cases 10
33.0 1 0.145 1.
90 minor - 110 remaining 0.08 2°
As is clear from Table 1, 3.0 to 50.0 wt of iron was used.
Example N of the present invention using a chromium-iron alloy containing % as a target (L 1 to 7, Comparative Example N118 using a cast product of pure chromium, ditarget manufactured by powder sintering method from pure chromium) Compared to N[Lll (conventional example), the sputtering speed on the aluminum substrate is significantly faster.The above N(L1 to 7 show almost the same reproduction output as N[Lll) sputtered with pure chromium. The magnetic properties are also almost the same as those of the conventional example.

On the other hand, comparative height measurement 9, in which the amount of iron added is less than the claimed range of the present invention, does not have a faster sputtering speed than conventional example NcL11, and comparative height measurement 10, in which the amount of iron added is higher than the range of the present invention, is , Nα11, the sputtering speed is faster, but the reproduction output is lower.

〔Effect of the invention〕

As described above, according to the present invention, in a magnetic recording medium having a cobalt or cobalt alloy magnetic thin film on an aluminum substrate, it is possible to significantly increase the sputtering speed when sputtering a chromium-based thin film as an underlayer of the magnetic thin film. This greatly improves the productivity of magnetic disks.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magnetron sputtering apparatus used in the present invention. 1...Target, 2...Aluminum substrate, U...Copper plate, 4a...
Magnet, 4b... Magnet patent applicant Furukawa Electric Co., Ltd. Figure 1

Claims (3)

[Claims] (1) A magnetic recording medium having a cobalt or cobalt alloy magnetic thin film on an aluminum substrate, characterized in that a chromium alloy thin film containing 3.0 to 30.0 wt% iron is applied as an underlayer of the magnetic thin film. recoding media. (2) After plating the aluminum substrate as a primary base layer, 3.0 to 30.0wt of iron is applied as a secondary base layer.
2. The magnetic recording medium according to claim 1, further comprising a chromium alloy thin film containing % of chromium alloy. (3) After performing anodic oxidation treatment on the aluminum substrate as a primary base layer, iron is applied as a secondary base layer of 3.0 to 30%.
2. The magnetic recording medium according to claim 1, further comprising a chromium alloy thin film containing 0 wt%.