JPS6249968B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording materials, and more particularly to cobalt chromium perpendicular magnetic recording media.

A magnetic recording medium forms a magnetic film such as a magnetic disk or magnetic tape used in a storage device of a computer, and is generally magnetized in the longitudinal (in-plane) direction of the recording medium. However, with this magnetization method, there is a limit to increasing the recording density, and a method of magnetizing in the direction perpendicular to the surface of the recording medium has been proposed, which makes it possible to achieve a much higher density (for example, Shunichi Iwasaki, "High-density magnetic recording using perpendicular magnetization", "Nikkei Electronics" No.
192, August 7, 1978, pp. 100-111). Cobalt chromium is used for perpendicular magnetic recording media that can be magnetized in the direction perpendicular to the magnetic film surface, and cobalt is deposited on the substrate by sputtering.
A chromium (Co-Cr) film is formed. Cobalt has large crystal anisotropy energy, and its hexagonal crystal structure has the potential to form a perpendicularly magnetized film. In order to realize this in a thin film, the following conditions are required.

Ku>2πMs ² In the formula, Ku is the crystal anisotropy constant of the magnetized film, and Ms is the saturation magnetization of the magnetized film. In order to satisfy this condition, non-magnetic chromium is added with the C axis (axis of easy magnetization) of the crystal aligned perpendicular to the film surface to lower the saturation magnetization Ms. Generally, the amount of chromium added is 30wt% or less, and 15~
25wt% is preferred.

Figure 1 shows the relationship between the saturation magnetization Ms of a conventional cobalt-chromium film and the amount of added chromium (wt%).
Further, FIG. 2 shows the relationship between the dispersion angle Δθ ₅₀ of the locking curve by X-rays representing the alignment of the C-axis of this cobalt-chromium film and the amount of added chromium (wt%). The sputtering conditions for forming the cobalt-chromium film were the same as in the examples described later, but the amount of Cr pellets on the Co target was changed.

As can be seen from Figures 1 and 2, by adding chromium, the saturation magnetization Ms can be lowered and C
The dispersion angle Δθ ₅₀ of the axis can be made smaller (the C axis can be further aligned perpendicular to the film surface).

The present invention further increases the dispersion angle Δθ ₅₀ of the C-axis of the crystal by adding 30 wt% or less of rhodium (Rh) as a third element to the above-mentioned cobalt-chromium perpendicular magnetic recording medium of the cobalt-chromium magnetized film. The objective is to reduce the size so that a magnetic film having an axis of easy magnetization perpendicular to the film surface can be produced.

The amount of rhodium, the third element, is 30wt%
Must be below. When rhodium is added to cobalt alone, as shown in Figure 3,
Up to 30wt%, the dispersion angle Δθ ₅₀ becomes small and the orientation of the C-axis improves, but when more than 30wt% is added, the orientation of the C-axis becomes bidirectional, resulting in a decrease in the dispersion angle Δ
θ ₅₀ becomes large, which is not preferable as a perpendicular magnetization medium. Therefore, the amount of rhodium as the third element needs to be 30 wt% or less.

The present invention will be explained below with reference to Examples.

A 6-in.
Cr pellet on Co target (7x7x0.5mm)
was placed in an area ratio of 18%, and Rh pellets (7×
7 x 0.5 mm) were placed at an area ratio of 2.5% and 5%. Note that these pellets were placed evenly on the Co target so as not to shift. Then, the above target was sputtered under the following conditions to form a 1 μm thick Co _80-x Cr ₂₀ Rhx film on the polyimide film substrate. The composition of the resulting film was measured using an X-ray microanalyzer.

Substrate temperature (at the start of sputtering) 25°C Sputterpower 200W Argon gas pressure 2×10 ^-2 torr Note that this substrate was heated in vacuum (250°C) to release the gas in the substrate before sputtering.

Dispersion angle Δθ of the C axis of the obtained Co _80-x Cr ₂₀ Rhx film
The relationship between ₅₀ and Rh content (xwt%) is shown in Figure 4. It can be seen from FIG. 4 that as the amount of rhodium increases, the dispersion angle Δθ ₅₀ becomes smaller, and the C-axis becomes more perpendicular to the film surface than in the magnetic film with only chromium added. That is, the addition of rhodium facilitates the creation of a perpendicularly magnetized film.

In addition, the saturation magnetization Ms of the obtained Co _80-x Cr ₂₀ Rhx film
The relationship between the amount of Rh and the amount of Rh (xwt%) is shown in Figure 5. Rhodium is also non-magnetic, and as the amount of rhodium increases, the saturation magnetization Ms decreases as shown in FIG.

The coercive force Hc (Oe) and Rh content (wt
%) is shown in Figure 6. Note that line A in Figure 6 represents the coercive force Hc (⊥) in the direction perpendicular to the film surface, and line B represents the coercive force Hc in the longitudinal (parallel) direction.
Represents (). As can be seen from FIG. 6, the perpendicular coercive force is 500e or more, and the rhodium-doped magnetic recording medium of the present invention is suitable as a perpendicular magnetic recording medium for high-density recording.

Furthermore, FIG. 7 shows the MH curve (hysteresis curve) of the obtained CoCrRh film, Co ₇₀ Cr ₂₀ Rh ₁₀ film. Line C in Figure 7 is the result of measurement perpendicular to the film surface, and line D is longitudinal (parallel) to the film surface.
These are the results measured in the direction.

From these results, CoCrRh film is superior to conventional CoCr.
It can be seen that the C axis, which is an axis of easier magnetization than the film, is more likely to be perpendicular to the film surface, and that the saturation magnetization Ms and coercive force Hc can be controlled by changing the amount of rhodium added. Therefore, the rhodium-added cobalt-chromium magnetic recording medium according to the present invention is preferable as a perpendicular magnetic recording medium for high-density recording.

[Brief explanation of the drawing]

FIG. 1 is a chart showing the relationship between the saturation magnetization and the amount of chromium in a cobalt-chromium perpendicular magnetic recording film.
Figure 2 is a chart showing the relationship between the dispersion angle and the amount of chromium in a cobalt-chromium perpendicular magnetic recording film.
The figure shows the dispersion angle of a film made by adding rhodium to cobalt.
FIG. 4 is a chart showing the relationship between the rhodium content and the dispersion angle of the rhodium-doped cobalt-chromium perpendicular magnetic recording film according to the present invention; FIG. 6 is a chart showing the relationship between the saturation magnetization and the amount of rhodium in the rhodium-doped cobalt-chromium perpendicular magnetic recording film according to the invention; FIG. FIG. 7 is a chart showing the relationship between the amount of rhodium and the amount of rhodium, and FIG. 7 is a chart showing the MH curve (hysteresis curve) of the Co ₇₀ Cr ₂₀ Rh ₁₀ film according to the present invention. A, C...for the direction perpendicular to the film surface; B, D...for the longitudinal (parallel) direction to the film surface.

Claims (1)

[Claims] 1. A cobalt-chromium perpendicular magnetic recording medium containing 30 wt% or less of rhodium.