JPS61142524A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having Hc of suitable magnitude in the magnetic recording medium provided with a thin magnetic film of a cobalt alloy contg. 2-12atom% platinum by interposing a chromium layer between the substrate and the thin magnetic alloy film. CONSTITUTION:The thin magnetic film consisting of the cobalt alloy contg. 2-12atom% platinum is formed on the substrate and the chromium layer is interposed between the substrate and the thin magnetic alloy film. Hc is remarkably increased in the 0-12atom% range of the content of Pt by providing the chromium layer as compared to the case in which the chromium layer is not provided. The gradient of the Hc curve with respect to the content of Pt decreases and the change of Hc with the fluctuation in the content of Pt in the thin magnetic Co-Pt alloy film decreases. The magnetic characteristics of the thin magnetic film themselves do not change so much in spite of the minor fluctuation in the content of Pt of the thin magnetic Co-Pt alloy film on account of a fluctuation of various conditions in the process for production and the product having less variance in quality is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium having a magnetic alloy thin film, and particularly to a magnetic recording medium in which the alloy magnetic thin film contains platinum.

[Prior Art] Research and development of magnetic recording media having alloy magnetic thin films with high recording density has been greatly promoted in recent years.

One of these uses a magnetic thin film of cobalt (Go)-platinum (Pt) alloy. Co--Pt alloys have long been known to have high corrosion resistance, and magnetic thin films using this alloy are also known to have high corrosion resistance.

By the way, as shown in FIG. 1, this Co--Pt alloy magnetic thin film has the characteristic that its coercive force He is maximized when the pt content is 20 atomic %.
For example, Journal of the Japan Society of Applied Magnetics vo 117, No. 2.
In the case where about 20 atom % of Pt is contained, which is well known as described in 1983, etc.

If Hc is too high, the override characteristics will deteriorate.

That is, the Hc range required for a magnetic thin film is 1, usually 50
0 to 1000 [Oe], therefore, in conventional magnetic recording media having Co-Pt alloy magnetic thin films, the Pt content is usually around 10 atomic %, and the region where Hc is lower than the maximum value. It is used in

[Problems to be Solved by the Invention] As shown in Figure 1, in the area where the PT content is around 10 JI%, the change in He with respect to the change in the PT content is large, and therefore the amount of PT blended in the manufacturing process is There was a problem in that even a minute change in the amount of water caused a considerable change in product characteristics, resulting in a decrease in product yield.

[Means for Solving the Problems] As a result of intensive research into magnetic recording media having a Co-Pt based magnetic alloy thin film, the present inventors found that a chromium layer is formed as an underlayer of the magnetic alloy thin film. , excellent H
It has been found that a magnetic recording medium having an alloy magnetic thin film with c characteristics can be obtained.

The present invention has been made based on the above knowledge, and a magnetic thin film of a cobalt-based alloy containing 2 to 12 at% of platinum is formed on a substrate, and a chromium layer is formed between the substrate of the bracket and the alloy magnetic thin film. A magnetic recording medium characterized in that a magnetic recording medium is interposed therein.

The present invention will be explained in more detail below.

In the present invention, a chromium layer is formed between the Co--Pt alloy magnetic thin film and the substrate.

Figure 2 shows the measurement results showing the relationship between X and Hc when an alloy magnetic thin film with the composition Co I-x P t x is formed on an aluminum alloy substrate. As a result, it is recognized that when X is in the range of 0 to 0.12, that is, the Pt content is in the range of 0 to 12 atomic %, Hc increases significantly compared to that without a chromium layer.

Furthermore, from FIG. 2, it can be seen that due to the formation of the chromium layer, the gradient of the He curve with respect to the pt content becomes smaller, and the change in Hc with respect to the change in the pt content in the Co--Pt magnetic alloy thin film becomes smaller. Therefore, in the present invention, even if the Pt content of the Co-pt magnetic thin film changes slightly due to variations in various conditions during the manufacturing process, the magnetic properties of the magnetic thin film itself do not change significantly. Therefore, it is possible to obtain products with less variation in quality.

The reason why the provision of the chromium layer provides the excellent effects described above is because of the Co formed on the chromium layer.
This is presumably because the axis of easy magnetization in the -Pt magnetic thin film is strongly oriented in the in-plane direction of the film. The thickness of the chromium layer is 5
00 to 3000A is preferable; if it is thinner than 500A, the above-mentioned He increasing effect will be reduced; conversely, if it is thinner than 500A,
This is because if the thickness is thicker than this, the formation time by sputtering becomes excessively long, leading to an increase in cost.

Note that it has been conventional practice to provide an underlayer or intermediate layer made of various materials between a magnetic thin film and a substrate, and it is also possible to use an N1-P layer in a magnetic recording medium using a Co-PL thin film. It is publicly known (for example, Japanese Patent Application Laid-Open No. 59-61106)
, L However, according to the research of the present inventors, N1-P
It was found that the effects of the present invention as described above were not achieved at all in the base layer.

Furthermore, it is known that chromium is formed on a substrate in a magnetic recording medium using a Co-N1-P magnetic alloy thin film (Japanese Unexamined Patent Publication No. 58-41524). These documents do not mention at all that a chromium layer is provided between the magnetic alloy layer and the substrate in the medium, and that the formed chromium layer can significantly improve the Hc characteristics.

The magnetic thin film used in the present invention contains platinum from 2 to 2.
It is a cobalt-based alloy containing 12 atomic percent.

The reason why the content of platinum is 2 to 12 atom % is that if it is less than 2 atom %, the corrosion resistance will be poor, whereas if it is more than 12 atom %, Hc will become too high. A particularly preferred platinum content is between 3 and 11, especially between 4 and 10 atom %.

In addition, in the present invention, in the cobalt-based alloy containing platinum, a part of cobalt may be replaced with nickel and/or iron. In this case, when nickel and iron are added, HC
This has the effect of making it possible to easily adjust Hc according to the required characteristics of the medium. When a part of cobalt is replaced with nickel and/or iron, it is preferable that the upper limit of the substitution ratio is 25 atomic % of CO. The reason for this is as follows. That is, if the substitution ratio by nickel exceeds 25 atomic %, the saturation magnetic flux density Bs decreases, and the crystal system changes from hap to fcc, resulting in a decrease in the in-plane squareness ratio S. Further, in the case of iron, if the substitution ratio exceeds 25 atomic %, the corrosion resistance of the alloy magnetic thin film will be reduced.

The substrate used in the present invention is a non-magnetic material conventionally used in magnetic recording media, such as metal or alloy substrates such as aluminum, aluminum alloys containing several percent or less of magnesium, and titanium alloys. In addition, various ceramic substrates can also be used.

Furthermore, in the present invention, N1 is used between the substrate and the chromium layer.
- A hard non-magnetic intermediate layer made of P, other nickel-based alloys, aluminum oxide, etc. may be interposed. By interposing such a hard intermediate layer, the magnetic layer is formed by contact between the magnetic head and the magnetic recording medium. This makes it possible to prevent deformation of the magnetic recording medium and increase the durability of the magnetic recording medium.

Furthermore, in the present invention, various types of protective films may be formed on the alloy magnetic thin film.
In addition to metals, oxides, nitrides, carbides, etc., various materials conventionally used as protective films, such as boron, carbon, boron-containing alloys, carbon-containing alloys, and polysilicate, can be used. Furthermore, a lubricant made of various organic substances can also be applied onto this protective film.

The magnetic recording medium of the present invention can be manufactured by various conventional methods for manufacturing magnetic recording media having magnetic alloy thin films.

For example, it can be manufactured by a vapor deposition process such as sputtering, but the manufacturing method is not particularly limited.

[Function] In a magnetic recording device equipped with a magnetic thin film of a cobalt-based alloy containing 2 to 12 at. A magnetic recording medium is obtained. Further, in the magnetic recording medium of the present invention, Hc with respect to change in platinum content
fluctuation is small.

[Example] Hereinafter, the present invention will be explained in detail using specific examples.

Although the embodiment described below uses a magnetron r, f, and sputtering device, it is of course possible to obtain the effects of the present invention by ion beam sputtering, etc., which can be said to be similar in terms of ion technology.

Example 1 Aluminum alloy substrate containing 4% magnesium (size: diameter 130 mm, inner diameter 40 mm, thickness 1.9 mm)
) was formed with an aluminum oxide base layer having a thickness of lOILm, and the surface was polished to make it flat.

Next, using a flat plate magnetron r, f, sputtering device,
500-3000Ac7)Cr on the base layer under the following conditions
layer and then a ff1co-Pt thin film.

Initial exhaust 1~2X10-''Torr
Atmosphere during sputtering Ar Atmospheric pressure during sputtering 10-30 Tarr Input power 1kw Target composition (when forming a Cr layer) Cr target composition (when forming a magnetic thin film) Co-Pt (0% to match the composition of the target thin film) ) Pole spacing: 108 mm Thickness of magnetic thin film: 500 A Thin film formation rate: 100 to 300 A/min Substrate temperature: 200° C. After that, a carbon protective film is sputtered to a thickness of 50 OA, and is combined with the magnetic recording medium. did.

FIG. 2 shows the Hc characteristics of this magnetic recording medium.

Comparative Example 1 Magnetic recording media having magnetic alloy thin films with different platinum contents were produced in the same manner as in Example 1 except that no chromium layer was provided, and the Hc thereof was measured. The results are shown in Figure 2.

Comparative Example 2 A magnetic recording medium was prepared in the same manner as in Example 1 and Comparative Example 1, except that the magnetic alloy thin film did not contain platinum using K, and the target material was made of only cobalt, and its He was measured. . The results are shown in Figure 2.

Example 2, Comparative Example 3. Comparative Example 4 Using nickel as a target material containing lO atoms, OO, 9-x x O, IPt Ni
Magnetic recording media were produced in the same manner as in Example 1, Comparative Example 1, and Comparative Example 2, respectively, except that a magnetic alloy thin film having the composition was formed. FIG. 3 shows the measurement results of Hc of these magnetic recording media.

From FIGS. 2 and 3, in a magnetic recording medium having a Co-Pt magnetic alloy thin film, by forming a chromium layer as an underlayer, Hc increases when the platinum content is in the range of 12% or less, and It is observed that the slope of the Hc curve becomes progressively smaller with increasing thickness of the chromium layer. In addition, in the platinum content range of 2 to 12%, Hc of the magnetic recording medium according to the example is 500 to too.

(Oe), and is recognized to have excellent practical properties.

Example 3 A disk-shaped magnetic recording medium with a diameter of 130 mm was manufactured according to the procedure of Example 1 under the following conditions.

Target: Co-Pt (Pt 5 atomic%) Cr layer thickness: 800A (conditions other than the above are the same as in Example 1) The magnetic thin film of the magnetic recording medium thus obtained
It was found that it contained 5 at% of t and had the following magnetic properties.

Bs: ll'KG Gauss Hc: 700 (Oe) s: 0.8 Furthermore, the electromagnetic conversion characteristics of this magnetic recording medium were measured as follows.

Head used: Manganese ferrite mini Winchester (
Track width 16pm, gap length 1, 14m, gear
- / depth 204m, number of turns 14TX2) Flying height: 0.34μm 1F: 1.25MHz 2F: 2.5MHz Disk rotation speed: 3600rpm Measurement location: Measured at R = 30mm from the center of the disk This playback output characteristic was as follows.

Reproducing output E2F=2.5 MHz: 0.42 mV Resolution (R=30 mm): 8 B% Override knee 32 dB From the above, it was found that this magnetic recording medium had characteristics as a high-density recording medium.

[Effect] As detailed above, according to the present invention, 500 to 1000 (
Practical as it has a moderate Hc of about Oe), has small variations in characteristics even if there is a change in Pt content, and has characteristics as a high-density recording medium with a high squareness ratio S. A recording medium with high performance is provided.

[Brief explanation of drawings]

FIG. 1 is a schematic graph showing the relationship between pt content and He, and FIGS. 2 and 3 are graphs showing measurement results in Examples. Agent: Patent attorney Tsuyoshi Shigeno P
t (at'/,) COl-x Ptx+: wholesale X -, Heemichiro COo, 9-X Ptx N1o1+: 1+jruX
Procedural amendment April 2, 1985 Patent Application No. 263623 of 1988 2 Title of invention Magnetic recording medium 3 Relationship to the case of the person making the amendment Name of patent applicant Name Hitachi Metals, Ltd. 4 Address of agent Tokyo Port 4-8-19-6 Akasaka-ku Detailed description of the invention and drawings in the specification to be amended. 7. Contents of the amendment: The statement in the "Detailed Description of the Invention" in the description is corrected as follows. (1) Correct "coercive force" on page 2, line $16 of jf'I to r coercive force j. (2) Page 4, line 12 (7) rcO+-XPtXJ
Correct it to rc ot-xPtxJ. (3) “2 atomic % or less” on page 6, lines 17-18 is 12
1X child% - Correct to less than 1.
C(4) In line 19 of the same page, ``When it becomes more than r'' is revised to ``When it exceeds.'' (6) Correct "to medium" in line 12 of the same page to "1 of medium." (7) Correct "rllKG Gauss" in line 5 of page 13 to rl
Corrected to lKGJ. ■ Change Figures 2 and 3 of the drawings to separate sheets. Figure 2 above;

Claims (4)

[Claims] (1) Magnetic recording characterized in that a magnetic thin film of a cobalt-based alloy containing 2 to 12 atomic percent of platinum is formed on a substrate, and a chromium layer is interposed between the substrate and the alloy magnetic thin film. Medium. (2) The magnetic recording medium according to claim 1, wherein the chromium layer has a thickness of 500 to 3000 Å. (3) The magnetic recording medium according to claim 1 or 2, wherein the alloy magnetic thin film contains 2 to 12 atomic percent of platinum, with the balance being cobalt. (4) The alloy magnetic thin film contains 2 to 12 atomic percent of platinum, with the remainder consisting of cobalt and iron and/or nickel,
3. The magnetic recording medium according to claim 1, wherein the content of iron and/or nickel is an amount that replaces 25 atomic % or less of cobalt.