JPH0339329B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an improvement in a method for manufacturing a magnetic recording medium film using a Co--Ni thin film. (Prior art) It is possible to form a magnetic thin film medium on a substrate by sputtering a Co-Ni alloy in a mixed atmosphere of Ar and nitrogen, and then obtain a thin film magnetic recording medium by heat-treating this in vacuum. , JP-A-57-72307 and Journal of Applied Physics Vol. 53, No. 5, May 1982, Journal Applied Physics No.
Volume 53, Issue 10, October 1982, Japanese Journal of
It is known from a document published in Applied Physics, Vol. 21, No. 11, 1982. In the invention described in JP-A-57-72307,
In particular, it is characterized in that a thin film containing 3 to 40 atomic percent of nitrogen is formed on a substrate and then heat treated to precipitate cobalt and nickel nitrides. In addition, in other known documents mentioned above, nitrogen (N) is also included in the Co-Ni thin film after heat treatment, and the residual magnetic flux density Br=
It is disclosed that a magnetic recording medium of 7000G and a squareness ratio Br/B _3K (magnetic flux density to residual magnetic flux density in a magnetic field of 3 KOe) of about 0.75 can be obtained. With the increasing density of magnetic recording, in addition to thinner media, higher residual magnetic flux density, and higher coercive force, there is a need for improved squareness ratio in order to improve the S/N ratio. Br proposed by
= 7000G and the squareness ratio Br/Br _3K = about 0.75, which are insufficient in terms of thin film properties, and there is a strong demand for a magnetic recording medium using a thin film with even higher properties. (Problems to be Solved by the Invention) In the invention described in the above-mentioned patent publications and papers, the nitrogen content in the film during sputtering is suppressed to 40 atomic % or less, and the nitrogen content after heat treatment is suppressed to 3 atomic %.
By doing the above, magnetic properties are obtained by forming nitrides such as cobalt nitride or nickel nitride, and when the nitrogen content is less than 3 at%, the amount of precipitated nitrides decreases. Hc, squareness ratio S (ratio of Hr to coercive force Hc, that is, Hr/
Hc. Here, it is clearly disclosed that Hr (magnetizing force) at the point where the tangent at point Hc in the magnetization curve of the medium intersects a straight line drawn parallel to the horizontal axis (magnetizing force axis) through point Br. ing. The present invention is based on the Co-Ni film proposed in the above-mentioned prior art.
The object of the present invention is to improve the magnetic properties of a magnetic recording medium having a thin alloy film and to provide a method for manufacturing an even more excellent magnetic recording medium. (Means for Solving the Problems) In the present invention, the composition of the magnetic recording medium film that is the final product is such that it contains 10 to 30 at% of Ni, more than 1 but less than 3 at% of N, and the remainder is substantially In order to make the Co-Ni film essentially Co, an ultrafine crystalline or almost amorphous Co-Ni-N thin film containing an appropriate amount of nitrogen (30 to 50 at%N) is formed by sputtering, and this is then coated with an appropriate amount of Co. It is characterized by heat treatment at high temperatures. Since the amount of nitrogen in the magnetic medium film influences the characteristics of the film, it should be more than 1 at% and less than 3 at%. In order to achieve this amount of nitrogen, the atmosphere when sputtering onto the substrate with the Co-Ni target was a mixed gas of nitrogen and argon at a volume ratio of 1/1 to 3/1, and the substrate temperature was kept in the range from room temperature to 300°C. shall be. The composition of the thin film obtained by sputtering is determined by changing the amount of N to 30 to 50 at%.
so that the remainder is substantially Co-Ni. This thin film is heat-treated in a non-oxidizing atmosphere at a temperature of 300 to 450°C to release part of the nitrogen gas from the thin film. The magnetic recording medium film contains Ni at 10 at% or more and less than 30 at%, N at more than 1 at% but less than 3 at%, and the remainder substantially consists of Co. Ni amount
When the concentration exceeds 30 at%, the Co--Ni thin film tends to take an fcc structure rather than an hcp structure, making it impossible to obtain strong orientation within the film plane and reducing the squareness ratio.
When the amount of Ni is less than 10 at%, the properties become close to that of metal Co, and the coercive force required for a magnetic recording medium cannot be obtained. As the nitrogen content increases, the residual magnetic flux density Br and squareness ratio S of the magnetic properties of the film decrease,
At 3at%, Br is 9000 Gauss and S is 0.8. On the other hand, the coercive force Hc of the film increases with the nitrogen content. However, when it becomes less than 1at%, Hc becomes 550
Becomes less than Ersted. In this way, the amount of nitrogen is
If more than 3 at% remains, the characteristics of the magnetic medium film will deteriorate, so the amount must be less than this. In addition, in order to reduce the nitrogen content to 1at% or less, it is necessary to increase the heat treatment temperature of the sputtered film to 450℃ or higher.
This heating may cause deformation of the aluminum plate used as the substrate and deterioration or cracking of the alumite layer or Ni--P layer used as the underlayer of the magnetic film. For the above reasons,
The amount of nitrogen in the magnetic recording medium is preferably more than 1 at% and less than 3 at%. Next, FIG. 1 shows a graph showing the amount of nitrogen in the Co--Ni--N sputtered film containing approximately 40 at% nitrogen after heat treatment at various temperatures for 1 hour.
As is clear from this figure, the amount of nitrogen in the film becomes less than 3 at% when the film is heat-treated at 320° C. or higher for 1 hour. When heat treatment is performed at a temperature below 300°C, it takes more than 20 hours to reduce the N content to 3 at% or less, which is not industrially practical. If the temperature exceeds 450°C, the N content can be reduced to 3 at% or less in less than one hour, but if Al is used as the disk substrate, deformation of the Al occurs, making it impractical. Furthermore, even when glass or ceramics is used for the substrate, the film may peel off due to the difference in thermal expansion coefficient with the Co--Ni medium film, making it impractical. Therefore, a suitable heat treatment temperature range is 300-450°C. The composition of this magnetic recording medium film is Cr, Pt,
Elements that improve corrosion resistance, such as Ru and Pd, may be added singly or in combination in a total amount of 2 to 25 at%. (Example) In carrying out the present invention, an aluminum plate, a glass plate, a ceramic (for example, Al ₂ O ₃ type) plate, etc. can be used as a substrate. Among these, aluminum plates are suitable because they are inexpensive. However, even with an Al-Mg alloy containing 3 to 4 wt% Mg, when a magnetic recording medium film is attached and used as a magnetic disk, CSS between the magnetic head and the
(contact-start-stop) cycles may occur and deformation due to the magnetic head may occur. Therefore,
After thoroughly polishing an aluminum plate, an alumite layer or a Ni--P layer is used as a base layer, and a magnetic film is formed on the base layer. The alumite layer and the Ni-P layer can be formed by a known method. A magnetic film is formed according to the method of the present invention. Sputtering may be performed using any method such as normal RF sputtering, magnetron DC, or RF sputtering, but magnetron DC,
Alternatively, RF sputtering has a high film formation rate and is efficient. The target material is Co-, which is made by melting metal cobalt and metal nickel to create an appropriate composition.
Use Ni alloy. This composition is the Co and Ni of the Co-10 to 30 at% Ni-N film, which is the desired final product.
It can be determined according to the ratio of Sputtering is performed using this target in a mixed gas atmosphere of nitrogen and argon. The ratio of nitrogen and argon in this gas mixture is 1/1 to 3/
By setting the ratio to 1, the generated sputtered film will contain 30 to 50 at% nitrogen. Further, the temperature of the substrate during this sputtering may be room temperature.
However, although heat may be absorbed during sputtering and the substrate temperature may rise to over 100°C, at temperatures up to 300°C, which is lower than the subsequent heat treatment temperature, Co
-Ni-N film is produced. After 30 to 50 at % of nitrogen is contained in the Co--Ni film, a thermal treatment is performed to release and reduce the nitrogen, thereby making it possible to obtain a magnetic medium film with in-plane anisotropy. Example 1 A thin film was sputtered onto an anodic aluminum oxide plate using a flat magnetron sputter in a mixed gas atmosphere of N ₂ and Ar under the following conditions. Initial exhaust 1~2×10 ^-6 Torr Total atmospheric pressure 16m Torr Volume ratio of _N2 and Ar 1:1 Input power 1KW Target composition Co-30at%Ni Target diameter 120mm Pole spacing 120mm Film thickness 1000〓 Substrate dimensions 7mm×8mm ×2 mm thick substrate temperature room temperature The sputtered film prepared under the above conditions contained 39 at% nitrogen, and the ratio of Co and Ni was almost the same as the composition of the target. When this film was subjected to X-ray diffraction or electron diffraction, it was found that it was microcrystalline or hardly crystallized. This sample was heat treated in vacuum for about 1 hour, and the relationship between heat treatment temperature and nitrogen content when the heat treatment temperature was varied is shown in FIG. As is clear from this figure, a temperature of 320° C. or higher was required to reduce the amount of nitrogen in the media film to less than 3 at%. Next, regarding the samples with various nitrogen contents obtained in this way, its residual magnetic flux density Br, coercive force Hc, and squareness ratio S (ratio of Hr to coercive force Hc, that is, Hr/Hc. Here, Hr is the magnetizing force at the point where the tangent at point Hc in the magnetization curve of the medium intersects with a straight line drawn parallel to the horizontal axis (magnetizing force axis) passing through point Br. Nitrogen content and Br,
The relationship between Hc and S is shown in Figure 2. From this figure,
A magnetic film containing more than 1 at% and less than 3 at% nitrogen is
Br over 9000 Gauss, S over 0.8 and 550~1000
It is clear that it shows the Hc of Ersted. Example 2 Among the conditions shown in Example 1, the total atmospheric pressure and nitrogen gas partial pressure were changed as shown in Table 1, and
Heat treatment was performed at 400° C. for 1 hour to create a magnetic medium film. Table 1 also shows the nitrogen content of the films thus produced before and after heat treatment.

【table】

[Table] As is clear from this table, the amount of nitrogen gas during sputtering is 50 to 75 vol.%, that is, the amount of _N2 and Ar
When the ratio of amounts was set to 1/1 to 3/1, the nitrogen content in the sputtered film was 30 to 50 at%. (Effects of the Invention) According to the method of the present invention, as shown in the example described above, it has a high residual magnetic flux density of 9000 Gauss or more, a squareness ratio of 0.8 or more, and a coercive force of 550 to 1000 Oersteds. When a magnetic recording medium film is obtained and used as a high recording density medium in a magnetic disk or the like, the performance effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the heat treatment temperature and the nitrogen content in the film after heat treatment, and FIG. 2 is a graph showing the relationship between the nitrogen content in the film and the magnetic properties of the film.

Claims (1)

[Claims] 1 In a mixed gas of nitrogen and argon (volume ratio of nitrogen and argon: 1/1 to 3/1), from room temperature to 300
Sputtering is performed with a Co-Ni target on a substrate at a temperature in the range of °C, containing 30 to 50 at% of N.
After forming a Co-Ni thin film, it is heat-treated at a temperature of 300°C to 450°C in a non-oxidizing atmosphere.
1. A method for producing a magnetic recording medium film, which comprises obtaining a magnetic film containing 10 to 30 at% Ni, more than 1 but less than 3 at% N, and the balance being substantially Co.