JPH01263921A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an overwrite characteristic and the packing density of iron to the upper part of fine pores by packing nickel or nickel alloy to the branch part on the bottom side of the fine pores of the anodized film formed on the surface of aluminum or aluminum alloy and iron into the upper part on the front layer side. CONSTITUTION:The anodized film 2 is formed on the surface of the aluminum layer 1 and the part of the film 2 in contact with the aluminum layer 1 is a semiconductive barrier layer 3 of a thin layer. The many fine pores 4... are above the barrier layer 3. Each of the pores 4 consists of the upper part 4a on the medium surface layer side, the branch part 4b on the bottom layer side and the intermediate part 4c connecting the upper part 4a and the branch part 4b. The nickel or nickel alloy 5 having low coercive force is packed in the branch part 4b and the intermediate part 4c and the iron 6 having a high saturation magnetic density is packed in the upper part 4a. The coercive force over the entire part of the magnetic material packed in the fine pores is thereby maintained at about >=1,000oersted being desirable, by which the good overwrite characteristic is obtd. and the packing density of the iron is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a magnetic recording medium (particularly suitable for perpendicular magnetic recording).
Hereafter, we will simply refer to the medium. ), by filling the bottom branch of the anodic oxide film of aluminum or aluminum alloy with nickel or nickel alloy with low coercive force, and filling the upper part of the surface layer with iron with high saturation magnetic density. This is designed to improve the override characteristics of the medium.

[Conventional technology]

Conventionally, aluminum or aluminum alloys are anodized and iron (F) is added into the micropores of the anodized film.
Media filled with a magnetic material such as e) are known to be particularly suitable for perpendicular magnetic recording (for example,
(See Japanese Patent Publication No. 51-21562).

In addition, copper (Cu) is added to the bottom of the micropores of the anodic oxide film.
), tin (Sn), or other non-magnetic material, and the upper part thereof is filled with a magnetic material such as iron.

[Problem to be solved by the invention]

However, a medium filled with iron has a problem in that the coercive force (HC) of the medium becomes too large and the override characteristic deteriorates to -30 to -35 dB.

On the other hand, a medium in which a non-magnetic material such as copper or tin is filled at the bottom and a magnetic material such as iron is filled on top has good override characteristics, but a magnetic material such as iron is filled on top of the non-magnetic material. When doing so, there is a drawback that the filling rate of the magnetic material is low due to spalling < r, and there is also a drawback that the readout current f[ is low.

[Means to solve the problem]

In this invention, the solution is to fill the bottom branch of the micropores in the anodic oxide film with nickel or nickel alloy, which has a low coercive force, and fill the upper part of the surface layer with iron, which has a high saturation magnetic density. did.

[For production]

By adopting the above configuration, the coercive force as a result of the magnetic material filled in the RAM hole is desirably about 1000 oersted, and good override characteristics are achieved, and the filling rate is improved compared to that of iron.

〔Example〕

FIG. 1 schematically shows the medium of the present invention, and reference numeral 1 in the figure is an aluminum or aluminum alloy layer forming a substrate (long substrate). A positive i4iM chemical film 2 is formed on the surface of this aluminum layer 1. This anodic oxide film 2 is integrally formed on the underlying aluminum layer 1 by anodizing treatment using a 11ffi bath such as a sulfuric acid electrolytic bath or an oxalic acid electrolytic bath. In addition, the part of the anodic oxide film 2 in contact with the aluminum layer 1 is a thin semi-conductive barrier layer 3.
A large number of fine holes 4 are formed above this barrier layer 3. The micropores 4 are columnar cavities and are arranged so that their longitudinal direction is perpendicular to the surface of the medium film. Further, the micropore 4 has an upper part 4a on the medium surface side, a branch part 4b on the bottom layer side, and an intermediate part 4c connecting the first part 4a and the branch part 4b. Part 1 4
a has a straight tube shape with an inner diameter of about 30 to 5 Qnm, a depth of about 1 to 2 μm in the final finished state (after grinding), and a center-to-center distance of 90 to 120 nm.
It is of m culm degree. In addition, the branch portion 4b has one part 4a.
It branches into 3 to 5 branches from the bottom toward the bottom layer, with an inner diameter of about 10 to 30 nllll and a depth of about 0.
．． 5~1μm1 The hole spacing of each branch is 5O-1 in center-to-center distance.
It is approximately 0Or+m.

The micropores 4 having such a shape can be formed by lowering the electrolytic voltage during the anodizing process during the process. The distance between the micropores formed by anodizing is generally proportional to the electrolytic voltage, am W? '
When the pressure increases to +i'X, the spacing becomes wider, and conversely, the number of micropores per unit area decreases.

It is also known that the depth of micropores is proportional to the electrolysis time.

Therefore, for example, by first proceeding with electrolysis at an electrolytic voltage of 40 to 60 V and then lowering the electrolytic voltage to 10 to 30 V, micropores 4 having branched portions 4b as shown in FIG. 1 are formed. can be written.

Therefore, nickel or nickel alloy 5 with low coercive force is applied to the branch portion 4b and intermediate portion 4C of such micropores 4.
is filled. The nickel alloy used here has a nickel value of 60% or more. Further, the upper portion 4a is filled with iron 6 having a high saturation magnetic density. To fill nickel or nickel alloy 5 and iron 6, after anodizing treatment, nickel or nickel alloy is first electrolyzed using a nickel salt single electrolytic bath or a mixed salt electrolytic bath consisting of nickel salt and other metal salts. Electrodeposition is performed on the branch portion 4b and intermediate portion 4c, and then electrolysis is performed using an iron salt-only electrolytic bath to deposit iron on the upper portion 4a, and by adjusting the electrolysis time of each The filling thickness (filling edge) can be controlled. In addition, since these electrodepositions start from the deepest part of the micropores 4, that is, from the part close to the Paris X7 layer 3, the nickel or nickel alloy 5 is reliably filled into the bottom of the branched part 4b.

In addition, in FIG. 1, Ll+12+13 indicates the initial thickness of the anodic oxide film 2, which is usually about 3 to 6 μm thick,
L 2 +13 indicates the thickness of the anodic oxide film 2 after filling with nickel or nickel alloy 5 and iron 6 and surface grinding, which is usually about 2 to 3 μm;
Indicates the thickness of

In a medium with such a structure, the branch portion 4 with a small inner diameter
nickel or nickel alloy 5 with low coercive force is filled in b, and iron 6 with high saturation magnetic density is filled in the upper part 4a with a thick inner diameter.
, the coercive force of the entire magnetic material filled in the micropores 4 is approximately 10,000 e or less, exhibiting good override characteristics. In addition, the upper part 4a of the micropore 4
The iron 6 is reliably filled, and the occurrence of voids that are not filled with the iron 6 is almost eliminated.

(Experiment example 1) Below, we will show experimental examples to clarify the effects.

A 4MO-96Aj alloy substrate was subjected to the following treatments to produce a medium of the present invention.

■Pretreatment: Degreasing, alkaline etching, smut removal ■Anodizing: 3% oxalic acid bath, 20℃, DC 48V constant voltage'
J Hyde, anodic oxide film thickness 3μm ■ Micropore expansion: 1% phosphoric acid bath, 30℃, constant current 60m1
/ After stepping down the voltage from DC 48V to 20V in 6 m2, constant voltage electrolysis in 3 portions at DC 20V ■First electrolysis; Bath composition Nickel sulfamate 0.2 sil/J Boric acid 30 g/j 1) H4, 0, 30℃ , modified AC electrolysis for 2 minutes ■Second electrolysis; Bath composition 5A ferrous ammonium acid 0.2
Mol/J Boric acid 30y/,, f pl+ 4.0.30℃, modified AC electrolysis, precipitation until exposed on the surface of micropores ■Grinding; 2 μTrL grinding of the anodic oxide film from the surface ■Keep a II! J formation: 5iQ2 with a thickness of 50n by sputtering
v4) Formation of It IIQ: Applying a fluorocarbon lubricant using a spin cord The override characteristic (0/W) of the medium obtained in the above manner was measured.

For comparison, a medium was prepared in which the first electrolysis was omitted and iron was electrodeposited and filled in the branched portions of the micropores, and the A-pearlite characteristics were measured.

The results are shown in Figure 2. FIG. 2 is a graph showing the relationship between the write head current and the override characteristic. As the write head current increases, the override characteristic of the medium of the present invention improves and takes a value of about -40 dB. On the other hand, in the case of a medium filled with only iron, the decrease was only down to about -35 dB, indicating that the A-pearlite characteristics were not good.

(Experiment Example 2) In the first electrolysis, the electrolytic bath composition was changed to create a medium filled with iron, copper, tin, and nickel in the branch and intermediate parts of the micropores, and The filling rate of the deposited iron was measured. The iron filling rate was measured by observing the medium after grinding with a microscope, and was expressed as the percentage of the number of empty micropores not filled with iron to the total number of micropores per medium area.

The results are shown in Table 1. Table 1 shows that when the branch parts and intermediate parts are filled with non-magnetic material such as copper, the filling rate of iron in the upper part decreases due to spalling, etc., but when filled with nickel, this problem does not occur. It turns out that this does not occur.

Table 1 [Effects of the Invention] As explained above, the magnetic recording medium of the present invention has nickel or a nickel alloy applied to the bottom branch of the micropores of the anodic oxide film formed on the surface of aluminum or aluminum alloy. Since the upper part of the surface layer side is filled with iron, the override characteristic is good and the upper part of the micropores is also filled with iron.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing an example of the magnetic recording medium of the present invention, and FIG. 2 is a graph showing the override characteristics of the magnetic recording medium in an actual example. DESCRIPTION OF SYMBOLS 1... Aluminum layer, 2... Anodic oxide film, 4... Fine pores, 4a... Upper part, 4b... Branch part , 5...nickel or nickel alloy, 6...
···iron.

Claims (1)

[Claims] A magnetic recording medium in which nickel or a nickel alloy is filled in the bottom branch of micropores in an anodic oxide film formed on the surface of aluminum or an aluminum alloy, and iron is filled in the upper part of the surface layer.