JP2816151B2 - Method for manufacturing perpendicular magnetic recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a perpendicular magnetic recording medium comprising a partial oxide of a metal containing Co as a main component, and particularly to the perpendicular magnetic recording medium having excellent magnetic properties. Is what you do.

[Conventional technology]

There is a remarkable improvement in recording density in the field of magnetic recording. In particular, the perpendicular magnetic recording method has the characteristic that the self-demagnetization effect decreases as the recording density increases, unlike the in-plane recording method currently in practical use. Research is being done.

As a perpendicular magnetic recording medium, a Co-Cr alloy has been announced by Iwasaki et al. [Iwasaki, Ouchi; .Ouchi: IEEE
Trans. Magn., MAG-14, 849 (1987)). The CoCr alloy has large magnetic anisotropy and saturation magnetization, and has excellent characteristics as a perpendicular magnetic recording medium. However, it is a metal and is vulnerable to wear. From such a viewpoint, for example, a partial oxide film of Co has been studied, and a perpendicular magnetization film having a large magnetic anisotropy has been obtained. [Yoshida et al .: JP-A-59-140629, and Nakamura et al .: Japanese Journal of Applied Physics, Vol. 23, No. 6, L397 (1984) (K. Nakamura e
t.al.:Jpn.J.Appl.Phys.Vol.23,No.6,L397(198
Four))〕.

[Problems to be solved by the invention]

However, in the Co-based partial oxide film magnetic thin film, although a perpendicular magnetization film is realized with a saturation magnetization (hereinafter abbreviated as Ms) in a range of 10 × 10 ⁵ A / m or less, when the recording and reproduction are actually performed, the reproduction output is reduced. , And only insufficient characteristics for a magnetic recording medium can be obtained.

An object of the present invention is to improve the magnetic properties of a Co-based partial oxide film,
An object of the present invention is to provide a perpendicular magnetic recording medium which has a high recording / reproducing output and is practically used.

Here, the Co-based partial oxide film is a Co-based partial oxide film shown in the literature and the like described in the section of the prior art, and CoCx (0 <
It has a non-stoichiometric composition represented by X <1). Microscopically, it is inferred that metal Co and cobalt monoxide (CoO are mixed).

[Means for solving the problem]

The above object can be achieved by subjecting a Co-based partial oxide film formed by a conventional technique to a heat treatment at a temperature of preferably 100 ° C. or more and 300 ° C. or less. The atmosphere during the heat treatment may be in the air or in a vacuum, and the treatment time may be 30 minutes or more at a predetermined temperature.

[Action]

The clear reason why the recording / reproducing characteristics are improved by the heat treatment is not clear, but is considered as follows.

FIG. 2 shows the change of the magnetization curve before and after the heat treatment in the air of the Co partial oxide film. Compared with the magnetization curve 6 before the heat treatment, it can be seen that the heat treatment significantly improves the squareness of the shoulder portion of the magnetization hysteresis curve 7. This indicates that the magnetization reversal occurs sharply by performing the heat treatment. It is considered that such an improvement in the magnetic characteristics resulted in an improvement in the recording resolution and the reproduction output when the recording and reproduction were actually performed.

The change in the shape of the magnetization hysteresis curve is considered as follows. The Co partial oxide film produced by the conventional technology has a structure in which microcrystals of metal Co are covered with CoO oxide oxide, but supersaturated oxygen exists in the microcrystals of metal Co, causing a large strain on the microcrystals. It seems that the uniformity is bad. Therefore, it is considered that the magnetization reversal of the metal Co in the film cannot be performed uniformly. On the other hand, such a film should
It is considered that when the following heat treatment is performed, supersaturated oxygen in the metal Co diffuses to form a stable CoO oxide on the surface of the metal Co microcrystal. As a result, the oxygen concentration in the metal Co decreases, the crystallinity of the Co microcrystals is improved, and the Co
It is considered that the magnetization reversal of the microcrystal is performed uniformly.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Using a vacuum deposition apparatus shown in FIG. 1, a Co partial oxide film was formed on the polyimide substrate 1 using a known technique.
Co was melted by an electron beam heating method (using an electron beam heating source 2), and vapor deposition was performed. The amount of oxygen introduced for performing partial oxidation was adjusted by the needle valve 5.

The deposition conditions were a substrate temperature of 30 ° C and a Co deposition rate of 0.3 nm /
s and the oxygen partial pressure were 9 × 10 ⁻³ Pa. Under these conditions, a Co partial oxide film with a thickness of 240 nm was formed and
The magnetic properties before and after the heat treatment at a temperature of 1 hour were compared.

FIG. 2 shows the first quadrant of the magnetization hysteresis curve before and after the heat treatment, in which a magnetic field was applied in a direction perpendicular to the film surface.

The Ms of the Co partial oxide film before the heat treatment is 5.16 × 10 ⁵ A / m,
Coercive force (hereinafter referred to as Hc _⊥) is 9.71 × 10 ⁴ A / m. Ms of the Co partial oxide film after the heat treatment is 4.92 × 10 ⁵ A / m, _Hc⊥ is 9.51 ×
10 ⁴ A / m. The decrease in Ms of about 0.2% observed after heat treatment is due to the supersaturated oxygen in the partial oxide film reacting with metal Co,
This is probably because a CoO oxide was formed and the density of metal Co in the partial oxide film was substantially reduced. Note that such a decrease in Ms was also observed in the heat treatment in a vacuum at a pressure of 1.3 × 10 ⁻⁴ Pa.

The major difference between the magnetization hysteresis curve in FIG. 2 before and after the heat treatment is the shoulder portion of the hysteresis curve indicated by the arrow in the figure. Before the heat treatment, the shoulder portion is gentle, indicating that the magnetization reversal to the magnetic field change in this region is not uniform. On the other hand, the shoulder portion is sharp after the heat treatment, which indicates that the magnetization reversal is uniform and steep with respect to the change in the magnetic field in this region.

The recording / reproducing characteristics of the Co partial oxide film before and after the heat treatment thus manufactured were measured at a linear recording density of 80 kFCI using a magnetic head having a gap length of 0.3 μm. Output before heat treatment is 1.5μV _pp (winding 1 turn, relative speed 1m / s
Was 3) in the sample after the heat treatment.
μV _pp , and the reproduction output was doubled.

In the case of the Co partial oxide film used in this example, the change in the magnetization hysteresis curve shown in FIG. 2 was observed at a heat treatment temperature of 150 ° C. or higher. It was also confirmed that the recording / reproducing characteristics were improved. In the present embodiment, the Co partial oxide film is taken up, but one or two of the elements of Ti, Mn, Zr, Cr, Al, Pt, Nb, Ru, Re, and Fe are used in total. , 0.1 atomic% to 15
A change similar to the magnetization hysteresis curve shown in FIG. 2 was also observed in the Co partial oxide film containing atomic%.

〔The invention's effect〕

The perpendicular magnetization film according to the present invention is simple in manufacturing method, requires only metal Co and oxygen gas as raw materials, and can obtain a perpendicular magnetic recording medium having good characteristics by a simple heat treatment, and thus has a practical advantage. Is big.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an electron beam heating evaporation apparatus used for producing a Co partial oxide film of the present invention, and FIG. 2 is a first quadrant of a magnetization hysteresis curve before and after heat treatment of a Co partial oxide film produced by the present invention. Where the solid line is before heat treatment and the dashed line is after heat treatment. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Electron beam heating evaporation source, 3... Co vapor flow, 4... O ₂ gas flow, 5... Needle valve, 6. Magnetization hysteresis curve, 7: Magnetization hysteresis curve of Co partial oxide film after heat treatment.

Continuation of the front page (72) Inventor Kazuyoshi Yoshida 1-280 Higashi Koikebo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-62-214522 (JP, A) JP-A-62-103851 ( JP, A)

Claims (2)

(57) [Claims] In a method for manufacturing a perpendicular magnetic recording medium in which a magnetic layer composed of a partial oxide containing metal Co as a main component is formed on a non-magnetic substrate, a heat treatment is performed after forming the magnetic layer. A method for manufacturing a perpendicular magnetic recording medium. 2. A method for manufacturing a perpendicular magnetic recording medium according to claim 1, wherein the temperature of said heat treatment is 100 ° C.
A method for producing a perpendicular magnetic recording medium at a temperature of not less than 300 ° C.