JPS5832403A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase film-forming speed and make an easy magnetizing axis perpendicular to a film surface, by a method wherein a magnetic recording medium is formed on a substrate by employing a vacuum-deposited film having Co and Cr as its principal components, and the composition of the Cr in the vacuum-deposited film is specified to be 26-17wt%. CONSTITUTION:A vacuum-deposited film having Co and Cr as its principal components is formed on a substrate and employed as a magnetic recording medium. The composition of Cr in the film in forming the vacuum-deposited film is specified to be not less than 16wt% thereby to permit a vertically magnetized film to be obtained when the substrate temperature is 100-400 deg.C. Moreover, the composition of the Cr in the film is specified to be not more than 27wt% thereby to make the retentiveness larger than a predetermined value when the substrate temperature is 100-400 deg.C. Then, the composition of the Cr in the vacuum- deposited film is specified to range from 16-27wt% thereby to increase the film- forming speed as well as make the magnetic characteristics excellent and the easy magnetizing axis perpendicular to the film surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium suitable for perpendicular recording.

There is a perpendicular recording method as a magnetic recording method with excellent short wavelength recording characteristics. This method requires a perpendicular recording medium whose axis of easy magnetization is perpendicular to the film surface of the medium. When a signal is recorded on such a magnetic recording medium, the residual magnetization is oriented perpendicularly to the film surface of the magnetic recording medium. Therefore, the shorter the wavelength of the signal, the smaller the reversal magnetic field, and the better the reproduced output.

Currently used perpendicular recording media are made by using a magnetic layer (hereinafter referred to as "magnetic layer") which is mainly composed of CO and Cri and has an axis of easy magnetization in the perpendicular direction, either directly on a non-magnetic substrate or through a soft magnetic thin film such as permalloy. (referred to as a Co--Cr perpendicular magnetization film) is formed by a sputtering method.

A film mainly composed of CO and Cr formed by a sputtering method has a close-packed hexagonal crystal structure when the Cr composition is less than about 30M, and its C axis is oriented perpendicular to the film surface. It can be a perpendicularly magnetized film because it is possible to reduce the saturation magnetization at 1, where the anisotropic magnetic field in the perpendicular direction is larger than the demagnetizing field.

Since the formation speed of a magnetic thin film is slow in the method using sputtering, it is difficult to produce a perpendicularly magnetized film in a short time and at low cost. In contrast to the sputtering method, the vacuum evaporation method (including methods that ionize some of the evaporated atoms, such as the ion blating method) requires several thousand people/
The present inventors have discovered that a Co--Cr mailed film can be obtained at a formation rate as fast as seconds.

In order for the Co--Cr deposited film to become a perpendicularly magnetized film, it is necessary that the anisotropic magnetic field in the direction perpendicular to the film surface be larger than the demagnetizing field. That is, it is necessary that the perpendicular anisotropy constant Kn of the film be positive.

Furthermore, when a signal is recorded on a Co-Cr perpendicular magnetization film and reproduced, the reproduction output is approximately proportional to the coercive force HcJ- in the direction perpendicular to the film surface, and the larger the coercive force H6, the better the reproduction output. It will be done. In order to put a perpendicularly magnetized film into practical use, a coercive force in the direction perpendicular to the film surface of at least 3000 e is required.

The present invention has been made in consideration of the various matters mentioned above, and is a magnetic recording medium in which a vacuum-deposited film containing CO and Cri as main components is formed on a substrate, in which Cr in the vacuum-deposited film is The present invention provides a magnetic recording medium whose composition is 16% by weight or more and 27% by weight or less, and whose axis of easy magnetization is perpendicular to the film surface.

The magnetic recording medium of the ± invention will be explained using FIGS. 1 to 4.

1 shows the relationship between the perpendicular anisotropy constant Kn (vertical axis) of a Co--Cr film obtained by vacuum deposition and the amount of Cr contained in the film (horizontal axis). In the same figure, curve 1~
4, the substrate temperature Tsub during vapor deposition is 100°C,
Characteristics at 200°C, 350'C and 400°C are shown. As can be seen from looking at each characteristic curve, the perpendicular anisotropy constant Kn will not become positive unless the Cr composition in each substrate (Q Figure 2 shows the relationship between the substrate temperature and the amount of Cr that gives Kn-〇, which shows that it is not possible.From this figure, the minimum amount of Cr required to obtain a perpendicular magnetization film when the substrate temperature Tsub is around 330°C is shown. The amount of indicates the minimum value,
Its value is approximately 16 weight factors.

From Figures 1 and 2, Co -
It can be seen that in order to obtain a Cr perpendicularly magnetized film, it is necessary to increase the amount of Cr to 16% by weight or more.

Although experiments were conducted using a polyimide film, a Ti thin film, and a glass plate as substrates on which the deposited film was formed, no dependence of the above characteristics on the substrate was found. Experiments were conducted by varying the time within a range of seconds, but no dependence of the above characteristics on the deposition rate was observed.

FIG. 3 shows the relationship between the coercive force Hc (vertical axis) in the direction perpendicular to the film surface of a Co--Cr film obtained by vacuum evaporation and the amount of Cr (horizontal axis). In the figure, curves 6 to 8 have substrate temperatures Tsub of 100'C and 200'C, respectively.

The characteristics at 350°C and 400°C are shown. As can be seen from each characteristic curve, the amount of Cr on the 16-weight plate was determined from FIGS. 1 and 2.

- In a Cr film, unless the amount of Cr is below a certain amount, C
It can be seen that the holding force of the o-Cr film does not exceed 3000e on Hc. Holding force Hc above becomes 3000eC
FIG. 4 shows the relationship between the amount of r and the substrate temperature Tsub.

From Figures 3 and 4, in order to obtain a Co-Cr perpendicular magnetization film with a total coercive force of 3000e or more obtained by vacuum evaporation, it is necessary to reduce the amount of Cr to 27% by weight or less. I understand.

In addition, Fig. 1 in the experiments shown in Figs. 3 and 4.

As in the case of FIG. 2, substrate dependence and deposition rate dependence were not guaranteed.

As mentioned above, CO and C for practical use can be produced by vacuum evaporation.
It can be seen that in order to obtain a magnetic recording medium made of r, the amount of Cr should be set to 16% by weight or more and 27% by weight or less.

As explained above, the magnetic recording medium of the present invention has a vapor deposited film made of Co and Cr whose easy axis of magnetization is perpendicular to the film surface, and in which the Cr(4) content is 16% by weight or more and 27% by weight or less. , has a high film formation rate and excellent magnetic properties, and is of great utility to industrial professionals.

[Brief explanation of the drawing]

Figure 1 shows Cr in a magnetic recording medium obtained by vacuum deposition.
Figure 2 shows the relationship between the perpendicular anisotropy constant Kn and the perpendicular anisotropy constant Kn.
Figure 3 shows the relationship between ``sub'' and the amount of Cr at which the perpendicular anisotropy constant Kn becomes zero. A diagram showing the relationship between Hc and 41 yen shows the relationship between substrate temperature, coercive force Hci, and A'thK'l C in a magnetic recording medium obtained by vacuum evaporation.
rf4:(!: - is a diagram showing the relationship between 'I2@314...Curves showing the relationship between the amount of Cr and the perpendicular anisotropy constant Kn at each substrate temperature, 5 and 6 , 7.8...Curve showing the relationship between Cr content and coercive force HcJ at each substrate temperature. Name of agent Patent attorney Toshio Nakao and 1 other person 1st
Figure 2

Claims (1)

[Claims] A magnetic recording medium in which a vacuum deposited film containing CO and Cr as main components is formed on a substrate, wherein the composition of Cr in the vacuum deposited film is 16% by weight or more and 27% by weight or less, and the magnetization A magnetic recording medium characterized in that the easy axis is perpendicular to the film surface.