JP2527616B2 - Metal thin film magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium for metal thin film type in-plane recording excellent in noise characteristics.

[Conventional technology]

Recently, as a magnetic recording medium, a metal thin film type magnetic recording medium in which a thin film (magnetic layer) of a ferromagnetic metal such as CoNi, CoCr, and CoCrNi is formed on a non-magnetic substrate has become Coating type magnetic recording media are being replaced. The magnetic film as the recording layer is formed by various physical vapor deposition methods such as sputtering, ion plating and vacuum vapor deposition. In a recording medium in which the magnetic recording method is the in-plane magnetization method, an underlayer for introducing in-plane anisotropy in the magnetic film, typically a chromium film, is formed on the substrate, and the Cr film is formed. A stacked film of the magnetic film is formed on the surface.

[Problems to be Solved by the Invention]

The metal thin film type magnetic recording medium is capable of higher density recording than the conventional coating type magnetic recording medium, but further improvement in recording density is required for the next generation magnetic recording medium.

An object of the present invention is to provide a magnetic recording medium having improved noise characteristics for the above-mentioned metal thin film type magnetic recording medium, which enables high density recording.

[Means and Actions for Solving the Problems]

The present invention relates to a magnetic recording medium for in-plane recording, wherein a thin film made of a ferromagnetic metal is laminated as a recording layer on a non-magnetic substrate via an underlayer film, wherein the underlayer film has the following formula: Cr _100- xAgx ... [I] [where x is 0.1 to 3.0], and is characterized by being composed of an alloy having a composition.

As described above, in the magnetic recording medium of the present invention, the underlayer film that imparts in-plane anisotropy to the ferromagnetic metal thin film (magnetic film) that is the recording layer is formed of the CrAg alloy represented by the formula [I]. There is. Ag in the CrAg alloy that forms this underlayer does not form a solid solution with Cr and precipitates at the grain boundaries of Cr to clarify the grain boundaries of the underlayer. With the clarification of the grain boundaries of the underlayer, the clarification of grain boundaries and the isolation of magnetic domains of the magnetic film laminated on the underlayer surface are promoted, resulting in an increase in the coercive force of the magnetic film. The effect of reducing the recording / reproducing noise characteristic due to the reduction of the magnetization transition width and the like can be obtained.

The lower limit of the Ag amount (x) in the CrAg alloy of the underlayer is set to 0.1 in order to make the above effect sufficiently. However, when the amount is too large, the coercive force (Hc) of the magnetic film tends to decrease. It is considered that this is because the crystal of Cr of the base film is disturbed as the amount of Ag is increased. Therefore, the upper limit of Ag amount is set to 3.0.

The magnetic film laminated on the film surface of the underlayer is made of Co, C
oNi, CoCr, CoCrNi, etc., or various ferromagnetic alloys containing Ta, Nb, V, P, and other elements added for the purpose of improving their magnetic and electrical properties, and their alloy composition. Is free to choose.

The metal thin film type magnetic recording medium of the present invention includes a magnetic disk, a magnetic drum, a magnetic tape, a magnetic sheet and the like. Each of these is manufactured according to known steps and conditions except that the underlayer for introducing in-plane anisotropy into the magnetic film is made of a CrAg alloy having the composition represented by the above formula [I]. be able to. For example, regarding a magnetic disk, an aluminum alloy plate or the like is used as a substrate, and a hard Ni-P plating film (film thickness: for example, 15 to 25 μm) is provided on the surface by electroless plating, and the plating film surface is textured. After that, a CrAg alloy film, which is an underlayer for giving in-plane anisotropy to the magnetic film, is appropriately thickened (for example, 50
0 to 3000Å). A magnetic film (having a film thickness of, for example, 500 to 2000Å) as a recording layer is formed on the film surface. Then, as a protective film to prevent wear and damage of the magnetic film,
By forming a coating having lubricity and wear resistance, for example, a carbonaceous film (film thickness: for example, 150 to 600Å), an in-plane recording magnetic disk having a multilayer laminated structure is obtained. The laminated structure is not limited to the above example, and for example, a Cr film (film thickness of about 100 is formed on the magnetic film before forming the carbonaceous film.
~ 500Å), the weather resistance of the magnetic disk can be further enhanced. Also, after forming the carbonaceous film on the magnetic film surface, a lubricant (film thickness: 10
~ 100 Å) can be provided to improve the protective lubrication function for the magnetic head. The film formation of each layer can be performed by a sputtering method, an ion plating method, a vacuum vapor deposition method, or the like.

〔Example〕

[I] Manufacture of test magnetic disk Aluminum alloy substrate (outer diameter 130 mm, inner diameter 40 mm, thickness
1.9 mm) surface with Ni-P electroless plating film (film thickness 20 μm)
After forming and polishing and texturing the surface, the magnetron sputtering method (Argon atmosphere pressure: 1 × 10 ^-2 torr) was used to form a base film made of a CrAg alloy, a magnetic film made of a ferromagnetic alloy, and lubrication. A carbonaceous film (thickness 300 Å) as a film was laminated in this order to obtain a test magnetic disk. In order to make a proper comparison of the recording / reproducing characteristics between the test magnetic disks, the coercive force (Hc) of each test magnetic disk and the product of residual magnetic flux density (Br) and film thickness (δ) (Br The underlayer film and the magnetic film were formed such that δ) became equal to each other. Its Hc is 1050 Oe and Br
・ Δ was set to 450G ・ μ.

[II] Recording / reproducing characteristic test For each magnetic disk under test, a recording / reproducing test of a signal was conducted at a recording linear density of 28 KFCI using a ferrite head. Head specifications are: gap width: 13.5μ, gap length:
0.79μ, inductance: 8μH, flying height: 0.2
0μ, loading force: 9.5gf, coil turns: 26
And the rotation speed was 3600 rpm.

The test results of each magnetic disk under test are shown in Table 1 together with the alloy composition of the magnetic film. In the table, No. 1 to 6 are base films
Inventive examples formed of CrAg alloy, Nos. 11 to 13 are comparative examples in which the base film is a Cr single-phase metal. Note that "S / N" means the ratio of the reproduction signal output and the media noise strength.

Further, FIG. 1 is a graph showing the coercive force (Hc) of the magnetic film in relation to the film thickness (δ) of the underlying film.
(A) is the underlayer film (Cr ₉₉ Ag ₁ ) and magnetic film (Co ₈₄ Cr ₁₂ Ta ₄ ) of the same alloy composition as the above-mentioned magnetic disk No. 1, and (b) is the same as the magnetic disk No. 11 under test. Underlayer film of alloy composition (Cr ₁₀₀ )
The measurement results are shown for a magnetic disk having a magnetic film and a magnetic film (Co ₈₄ Cr ₁₂ Ta ₄ ).

From the above test results, it is understood that the magnetic disk of the invention example having the CrAg alloy underlayer has improved noise characteristics such as modulation noise and S / N ratio.

[Advantages of the Invention] The metal thin film magnetic recording medium of the present invention has excellent noise characteristics and low recording / reproducing noise, which enables high-density recording superior to that of conventional products. It is possible to obtain effects such as quality and high performance.

[Brief description of drawings]

FIG. 1 is a graph showing the coercive force (Hc) of a magnetic film in relation to the film thickness of its underlayer.

Claims (1)

(57) [Claims] 1. A magnetic recording medium for longitudinal recording in which a thin film made of a ferromagnetic metal is laminated as a recording layer on a non-magnetic substrate via an underlayer film, wherein the underlayer film has the following formula: Cr _100- A metal thin film magnetic recording medium excellent in noise characteristics, characterized by comprising an alloy having a composition represented by xAgx (where x is 0.1 to 3.0).