JP3183965B2 - Magnetic recording film, magnetic recording medium, and magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording film having an axis of easy magnetization in a direction perpendicular to the film surface, useful for a magneto-optical recording medium or a recording layer of a magnetic recording medium.

[0002]

2. Description of the Related Art Magnetic recording films are widely used as information recording players. Magnetic tapes such as video tapes, floppy disks and hard disks for computers, and credit cards and cash cards also record information using magnetic recording films. In such a conventional magnetic recording film, an in-plane magnetic recording method which has an easy axis of magnetization in the in-plane direction of the film and records information by magnetizing in the in-plane direction has been widely used.

[0003] However, in the field of magnetic recording, there is a demand for higher recording density. What is being developed for this purpose is a perpendicular magnetic recording type magnetic recording film, also called a perpendicular magnetization film. This is a magnetic recording film having an easy axis of magnetization in a direction perpendicular to the film surface and magnetizing in that direction to record information.

[0004] In a magnetic recording medium using such a perpendicular magnetization film as a recording layer, it is possible to increase the recording frequency and narrow the track, and to improve the recording density. Also in a magneto-optical recording medium, by using a perpendicular magnetization film having effective magneto-optical characteristics for the recording layer, high-density, large-capacity, and repeated erasure of information can be performed.

As such a magnetic recording film having an easy axis of magnetization in a direction perpendicular to the film surface, a CoCr film formed by vapor deposition or sputtering is known. But CoCr
Since the film does not have effective magneto-optical properties, it can be used for a mere magnetic recording medium but cannot be used for a magneto-optical recording medium. In other words, the CoCr film is not a practical magnetic recording film that can be applied in a wide range because the field of application is limited even if a technique such as film formation can be established.

Therefore, a TbFeCo film has been widely used as a magnetic recording film having excellent perpendicular magnetization characteristics and magneto-optical characteristics. This TbFeCo film not only has excellent perpendicular magnetization characteristics as a magnetic recording film, but also has the saturation magnetization, Curie point temperature,
It is a magnetic recording film having well-balanced properties such as coercive force and Kerr rotation angle.

Under these circumstances, in the conventional magneto-optical recording system, a laser beam having a wavelength of 830 nm has been usually used. However, in systems that achieve higher density recording, the wavelength is even shorter than the currently used laser light wavelength.
The use of short wavelength laser light of 400 to 550 nm has been considered. For this purpose, a magnetic recording film having effective magneto-optical characteristics in a shorter wavelength region than now is required.

However, a conventional magnetic recording film such as a TbFeCo film cannot obtain effective magneto-optical characteristics in such a short wavelength region. Therefore, as a magnetic recording film having perpendicular magnetization characteristics and magneto-optical characteristics in a short wavelength region, platinum (P
t) layer and cobalt (Co) layer alternately stacked
/ Pt multilayer films have been actively studied for practical use.

[0009]

The Co / Pt multilayer film has a disadvantage that it requires a complicated film formation because of having a multilayer structure. This is inconvenient when considering productivity and the like.

An object of the present invention is to provide a high perpendicular anisotropy as a practically sufficient perpendicular magnetization property in a film-formed state without requiring a complicated film forming method such as an artificial lattice structure. It is an object of the present invention to obtain a magnetic recording film having magneto-optical characteristics suitable for use in a shorter wavelength region. Another object of the present invention is to provide a magnetic recording medium and a magneto-optical recording medium in which the magnetic recording film constituting the recording layer has such characteristics.

[0011]

Magnetic recording film in the present invention SUMMARY OF THE INVENTION may, cobalt (Co), platinum (Pt), a ternary alloy consisting of rhenium (Re), its composition Co _a Pt _b Re _c ,
a ≦ 75, 5 ≦ b ≦ 45, 5 ≦ c, 40 ≦ 4a-5c, a + b
+ C = 100 (where a, b and c are atomic percentages) and have an easy axis of magnetization in a direction perpendicular to the film surface.

In the present invention, as a recording film for high-density recording, a perpendicular magnetization film whose easy axis is perpendicular to the recording layer forming surface, that is, the effective perpendicular magnetic anisotropy energy becomes positive (the perpendicular direction is It is preferable to use a positive sign). Therefore,
Composition _{Co a Pt b Re c, a} ≦ 75,5 ≦ b ≦ 45,5 ≦ c, a
It is necessary to set + b + c = 100.

When writing information in magneto-optical recording, the lower the Curie temperature, the higher the recording sensitivity. However, the Curie temperature is preferably somewhat high from the viewpoint of environmental resistance as a recording medium. Therefore, in order to increase the Curie temperature to room temperature or higher, the composition of the magnetic recording film should be Co _{a
Pt b Re c, 40 ≦ 4a-} 5c, there needs to be a + b + c = 100.

It is more preferable that the recording film has a large Kerr rotation angle θk from the viewpoint of magneto-optical characteristics. Therefore, the composition _{Co a Pt b Re c, a} ≦ 70,10 ≦ b ≦ 45,5 ≦
It is more preferable that c, a ≧ 3c, and a + b + c = 100.

Here, in order to obtain a perpendicular magnetization film in the above-described CoPtRe alloy composition, sputtering, vacuum evaporation, molecular beam epitaxy (MBE), or the like can be used. The evaporation source used at this time may be a CoPtRe alloy evaporation source or an independent evaporation source for each element.
For example, when forming an alloy thin film by sputtering, a CoPtRe alloy target may be used, or a so-called composite target in which a Pt and Re chip is mounted on a Co target may be used.

The magnetic recording film according to the present invention can be used as a recording layer of a magnetic recording medium or a magneto-optical recording medium by utilizing the above-mentioned features.

The characteristics of the magnetic recording film according to the present invention may be further improved by an additive element effect, an underlayer effect, a substrate heating effect (annealing effect) and the like. At this time, the added elements include Al, Si, Ti, V, Cr, Mn, Fe, Ni,
Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ru, Rh, Ag, In, Sn, S
b, Hf, Ta, W, Os, Ir, Au, Pb, Pd, Bi and the like are exemplified.

Alternatively, it is possible to improve the efficiency as a so-called artificial lattice structure magneto-optical recording medium by alternately laminating another metal thin film, a dielectric thin film and the CoPtRe alloy thin film.

[0019]

EXAMPLES and COMPARATIVE EXAMPLES FIG. 1 shows the compositions of CoPtRe alloy thin film samples prepared as examples and comparative examples of the present invention. In the figure, the bottom is the Pt composition ratio (atomic%, the left end is 100 at%, the right end is 0 at%), and the left hypotenuse is the Co composition ratio (at%,
The upper right is 100 atomic%, the lower is 0 atomic%, and the right hypotenuse is the scale axis of the composition ratio of Re (atomic%, upper is 100 atomic%, lower is 0 atomic%). Further, in the figures, ◎ indicates the working examples 1 and 3 to 8, and ８ indicates the working examples 2 and 9 to 13,
The crosses indicate the compositions of Comparative Examples 1 to 13.

Examples 1 to 13 and Comparative Examples 1 to 13 were produced as follows. First, in a chamber of a DC sputtering apparatus, a Co target (diameter: 100 mm) as a composite target, and Pt and Re chips thereon were appropriately mounted according to the film composition to be formed. Further, a glass substrate was placed on a base with a water cooling device facing the composite target. Then, in an Ar gas atmosphere with a gas pressure of 5 mTorr,
DC sputtering with an input power of 100 W was performed to form a 100 nm-thick CoPtRe alloy thin film on a glass substrate.

The composition of the obtained CoPtRe alloy thin film is a fluorescent X
X-ray analysis and ICP (Inductively Coupled Plasma Analysi
s) Determined by the combined use of luminescence analysis. Various magnetic properties were measured and evaluated using a circular polarization modulation Kerr spectrum measuring device, a vibrating sample magnetometer (VSM) and a magnetic torque meter.

Tables 1 and 2 show the composition ratio of each sample and the measurement results.
Shown in However, in Tables 1 and 2, the composition ratio is atomic%.
It is. In the table, Keff (10 ⁶ erg / cc) is the effective magnetic anisotropy energy (positive sign indicates the direction perpendicular to the film surface of the magnetic thin film. However, here, the value measured by the magnetic torque meter is used in the sample. Ms (emu / cc) is the saturation magnetization of the magnetic thin film and the measured value of the vibrating sample magnetometer (VSM) is the value obtained by dividing the magnetic film by the volume of the magnetic film. Hc (kOe) is the perpendicular coercive force and θk (deg)
Indicates the absolute value of the saturation Kerr rotation angle at a measurement wavelength of 400 nm.

As a magnetic recording film for high-density recording, a perpendicular magnetization film having an easy axis of magnetization perpendicular to the recording layer forming surface is desirable. In Comparative Examples 1 to 13 shown in Table 2, the effective magnetic anisotropy energy is negative, but in Examples 1 to 13 shown in Table 1, the effective magnetic anisotropy energy is practically preferable. It has become. That is, the composition is Co _a Pt
_{b Re c, a ≦ 75,5 ≦} b ≦ 45,5 ≦ c, 40 ≦ 4a- 5
By setting c, a + b + c = 100, the effective magnetic anisotropic energy can be made positive.

It is more preferable that the recording film has a large Kerr rotation angle θk from the viewpoint of magneto-optical characteristics. Therefore, as shown in Example 1 and Examples 2 to 8 in Table 1,
Composition _{Co a Pt b Re c, a} ≦ 70,10 ≦ b ≦ 45,5 ≦ c, a
It is more preferable that ≧ 3c and a + b + c = 100.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

As described above, the present invention does not require a complicated film-forming method such as an artificial lattice structure, and has a high perpendicular anisotropy as a practically sufficient perpendicular magnetization characteristic in a film-formed state. And a magnetic recording film having magneto-optical characteristics suitable for use in a shorter wavelength region than at present. Further, it is possible to obtain a magnetic recording medium and a magneto-optical recording medium in which the magnetic recording film constituting the recording layer has such characteristics.

[Brief description of the drawings]

FIG. 1 Compositions of Examples and Comparative Examples

(56) References JP-A-63-262446 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 10/16 G11B 5/66 G11B 5/852 G11B 11 / 105 H01F 41/18

Claims (4)

(57) [Claims] 1. A ternary alloy comprising cobalt (Co), platinum (Pt) and rhenium (Re), the composition of which is Co _a Pt
_{b Re c, a ≦ 75,5 ≦} b ≦ 45,5 ≦ c, 40 ≦ 4a- 5
c, a + b + c = 100 (where a, b, and c are composition ratios in atomic percent), and a magnetic recording film having an easy axis of magnetization in a direction perpendicular to the film surface. 2. A composition _{Co a Pt b Re c, a} ≦ 70,10 ≦ b ≦ 4
2. The magnetic recording film according to claim 1, wherein 5,5.ltoreq.c, a.gtoreq.3c, and a + b + c = 100. 3. A magnetic recording medium using the magnetic recording film according to claim 1 as a recording layer. 4. A magneto-optical recording medium using the magnetic recording film according to claim 1 as a recording layer.