JP3113069B2 - 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. Which is developed for its being recommended is a magnetic recording film of the vertical magnetic recording method. 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 magnetic recording type magnetic recording 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, the magnetic field is perpendicular to the film surface having effective magneto-optical characteristics.
By using a magnetic recording film having an easy axis for the recording layer,
High-density, large-capacity information can be repeatedly erased.

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.

As for the magneto-optical recording characteristics, it is desired that the coercive force be large at room temperature level in order to maintain the stability of recorded information. However, this Co / Pt multilayer film has a disadvantage that it is small. Therefore, several attempts have been made to improve the coercive force of the Co / Pt multilayer film. For example, sputtering with Xe gas is one of them. However, Xe is more expensive than Ar which is usually used, and this is also inconvenient when practicality is considered.

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

[0012]

According to the present invention, the magnetic recording film is made of cobalt (Co), platinum (Pt), ruthenium (Ru).
A ternary alloy consisting of Co _a Pt _b R
u _c , 20 ≦ a ≦ 70, 10 ≦ b ≦ 70, 10 ≦ c ≦ 60, a + b +
It is characterized in that c = 100 (where a, b, and c are composition ratios in atomic%) and that the film has an easy axis of magnetization in a direction perpendicular to the film surface.

In the present invention, the magnetic recording film preferably has a small external magnetic field at which the magnetization is saturated so that the external magnetic field required for writing information can be small. Therefore, when an external magnetic field is applied in a direction perpendicular to the film surface, the magnetization of the magnetic recording film is saturated at an external magnetic field of 6 kOe or less, so that the composition is Co _a Pt _b Ru _c , a ≦ 70, 10 ≦ b, 10 ≤ c, a +
It is necessary to set b + c = 100.

When information is written 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 Ru _c , 20 ≦ a, b ≦ 70, c ≦ 60, a + b + c = 100
It is necessary to

Further, it is more preferable that the effective perpendicular magnetic anisotropy energy is likely to be positive (perpendicular direction is a positive sign). Therefore, the composition is Co _a Pt _b Ru _c , 20 ≦ a ≦ 40,
More preferably, 10 ≦ b ≦ 30, 40 ≦ c ≦ 60, and a + b + c = 100.

Here, in order to obtain a film having an easy axis of magnetization in a direction perpendicular to the film surface in the above-described CoPtRu alloy composition, sputtering, vacuum deposition, molecular beam epitaxy (MBE), or the like can be used. The evaporation source used at this time may be a CoPtRu alloy evaporation source or an independent evaporation source for each element. For example,
When forming an alloy thin film by sputtering, Co
A PtRu alloy target may be used, or a so-called composite target in which a Pt and Ru 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, Re, Rh, Ag, In, Sn, S
b, Hf, Ta, W, Os, Ir, Au, Pb, Pd, Bi and the like are exemplified.

Alternatively, the efficiency can be improved as a so-called artificial lattice structure magneto-optical recording medium by alternately laminating another metal thin film, a dielectric thin film and the CoPtRu alloy thin film.

[0020]

EXAMPLES and COMPARATIVE EXAMPLES FIG. 1 shows the compositions of CoPtRu 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 Ru (atomic%, upper is 100 atomic%, lower is 0 atomic%). Further, ◎ marks in the figures represent Examples 1 to 3,
○ indicates the compositions of Examples 4 to 15 and X indicates the compositions of Comparative Examples 1 to 12.

Examples 1 to 15 and Comparative Examples 1 to 12 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 Ru chips were appropriately mounted thereon 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, DC sputtering was performed at an input power of 100 W in an Ar gas atmosphere at a gas pressure of 5 mTorr to form a 100 nm-thick CoPtRu alloy thin film on a glass substrate.

The composition of the obtained CoPtRu alloy thin film was determined by Auger electron spectroscopy and ICP (Inductively Coupled Plasma Analytical).
ysis) was 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 Hs (kOe) saturates when an external magnetic field is applied in the direction perpendicular to the film surface of the magnetic thin film. The magnitude of the external magnetic field (vertical saturation magnetic field), Hc (kOe) is the vertical coercive force, and θk (deg) is the saturation Kerr rotation angle at the measurement wavelength of 400 nm.

It is desirable that the magnetization of the magnetic recording film be saturated by a small external magnetic field. Comparative Examples 1 to 1 shown in Table 2
In 2, the vertical saturation magnetic field is as large as 6 kOe or more,
In Examples 1 to 15 shown in Table 1, the vertical saturation magnetic field is 6 kOe or less, which is practically preferable. That is, the composition was changed to Co _a Pt _b Ru _c , 20 ≦ a ≦ 70, 10 ≦ b ≦ 70, 10
By setting ≦ c ≦ 60 and a + b + c = 100, the vertical saturation magnetic field can be reduced to 6 kOe or less.

When used as a perpendicular magnetization film, the effective magnetic anisotropic energy is more preferably positive. Therefore, as shown in Examples 1 to 3 in Table 1, the composition was Co _a Pt _b Ru _c , 20 ≦ a ≦ 40, 10 ≦ b ≦ 30, 40 ≦ c ≦ 6.
Preferably, 0, a + b + c = 100.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

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 coercive force as a perpendicular magnetization characteristic sufficient for practical use in a film formed state. It is possible to obtain a magnetic recording film having high perpendicular anisotropy and also 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

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 11/105 G11B 5/64 H01F 10/16

Claims (4)

(57) [Claims] 1. A ternary alloy comprising cobalt (Co), platinum (Pt) and ruthenium (Ru), the composition of which is Co _a Pt.
_b Ru _c , 20 ≦ a ≦ 70, 10 ≦ b ≦ 70, 10 ≦ c ≦ 60, a + b
+ C = 100 (where a, b, and c are composition ratios in atomic%)
And a magnetic recording film having an easy axis of magnetization in a direction perpendicular to the film surface. 2. The composition is Co _a Pt _b Ru _c , 20 ≦ a ≦ 40, 10 ≦ b
2. The magnetic recording film according to claim 1, wherein ≤30, 40≤c≤60, 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.