JPH0612713A - Magnetic recording film, magnetic recording medium and magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide a high perpendicular holding power and high perpendicular anisotropy sufficient for practicable use by forming the above recording film of a ternary alloy consisting of Co, Pt and Ru having specific compsn. ratios and providing the film plane with an axis of easy magnetization in the direction perpendicular to the film plane. CONSTITUTION:The above-mentioned film consists of the ternary alloy consisting of the Co, Pt and Ru and the compsn. thereof is CoaPtbRuc, 20<=a<=70, 10<=b<=70, 10<=c<=60, a+b+c (where, a, b, c are compsn. ratios in atomic %). This magnetic recording film has the axis of easy magnetization in the direction perpendicular to the film plane. The magnetic recording film is preferably small in the external magnetic field at which magnetization is satd. so that the smaller external magnetic field required at the time of information writing is necessitated. The magnetization of the magnetic recording film is satd. at <=60kOe external magnetic field when the external magnetic field is impressed in the direction perpendicular to the film plane and, therefore, the compsn. thereof is required to be specified to the above-mentioned ratios.

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 easy axis of magnetization in a direction perpendicular to the film surface, which is useful as a magneto-optical recording medium or a recording layer of a magnetic recording medium.

[0002]

2. Description of the Related Art Magnetic recording films have been widely used as a leader in recording information. Information is recorded on magnetic tapes such as video tapes, floppy disks and hard disks for computers, credit cards and cash cards using magnetic recording films. In such a conventional magnetic recording film, an in-plane magnetic recording system has been widely used, which has an easy axis of magnetization in the in-plane direction of the film and magnetizes in the in-plane direction to record information.

However, in the field of magnetic recording, higher density recording is required. Therefore, what is being developed is a magnetic recording film of a perpendicular magnetic recording system, which is 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.

In the magnetic recording medium using such a perpendicularly magnetized film as a recording layer, the recording frequency can be increased and the track can be narrowed, and the recording density can be improved. Also in a magneto-optical recording medium, by using a perpendicular magnetization film having effective magneto-optical characteristics as a recording layer, high density, large capacity, and repetitive erasing of information are possible.

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

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

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

However, the conventional magnetic recording film such as the TbFeCo film could not 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
Co with a structure in which t) layers and cobalt (Co) layers are alternately laminated
The / Pt multilayer film has been actively researched for practical use.

[0009]

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

As the magneto-optical recording characteristic, it is desired that the coercive force is large at room temperature in order to stably maintain recorded information. However, this Co / Pt multilayer film has a drawback that it is small. Therefore, several attempts are currently being 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 normally used Ar, which is also inconvenient when considering practicality.

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

[0012]

The magnetic recording film in the present invention is made of cobalt (Co), platinum (Pt), ruthenium (Ru).
Is _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 by atomic%) and that the easy axis of magnetization is in the direction perpendicular to the film surface.

In the present invention, it is preferable that the magnetic recording film 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. Therefore, 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 writing information in magneto-optical recording, the smaller the Curie temperature, the higher the recording sensitivity. However, the Curie temperature is preferably high to some extent from the viewpoint of the environmental resistance of the recording medium. Therefore, in order to keep the Curie temperature above room temperature, the composition of the magnetic recording film is Co _a
Pt _b Ru _c , 20 ≦ a, b ≦ 70, c ≦ 60, a + b + c = 100
And need to.

Further, it is more preferable that the effective perpendicular magnetic anisotropy energy tends to be positive (the positive 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 perpendicular magnetization film in the above CoPtRu alloy composition, sputtering, vacuum deposition, molecular beam epitaxy (MBE) method 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 an alloy thin film is formed by sputtering, a CoPtRu alloy target may be used, or a so-called composite target in which Pt and Ru chips are placed 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 taking advantage of the above characteristics.

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

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 or dielectric thin film and the CoPtRu alloy thin film.

[0020]

EXAMPLES AND COMPARATIVE EXAMPLES FIG. 1 shows the composition 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 atomic%, the right end is 0 atomic%), and the left hypotenuse is the Co composition ratio (atomic%,
The upper end is 100 at%, the lower end is 0 at%), and the right hypotenuse is the Ru composition ratio (at%, the upper end is 100 at%, and the lower end is 0 at%). Furthermore, the ⊚ mark in the figure indicates Examples 1 to 3,
The ◯ marks show the compositions of Examples 4 to 15 and the X marks show the compositions of Comparative Examples 1 to 12.

Examples 1 to 15 and Comparative Examples 1 to 12 were manufactured as follows. First, a Co target (diameter 100 mm) as a composite target and Pt and Ru chips thereon were appropriately placed in the chamber of a DC sputtering apparatus according to the film composition to be produced. 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 CoPtRu alloy thin film having a film thickness of 100 nm on the glass substrate.

The composition of the obtained CoPtRu alloy thin film was measured by Auger electron spectroscopy and ICP (Inductively Coupled Plasma Analyses).
ysis) Confirmed by the combined use of luminescence analysis. Various magnetic properties were measured and evaluated by a circular polarization modulation Kerr spectrum measuring device, a vibrating sample magnetometer (VSM) and a magnetic torque meter.

The composition ratios and measurement results of each sample are shown in Tables 1 and 2.
Shown in. However, in Table 1 and Table 2, the composition ratio is atomic%
Is. Also, in the table, Keff (10 ⁶ erg / cc) is the effective magnetic anisotropy energy (the positive sign represents the direction perpendicular to the film surface of the magnetic thin film. The value is divided by the volume of the magnetic recording film, and the demagnetizing energy is not corrected.), Hs (kOe) is saturated when the 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.

For the magnetic recording film, it is desirable that the magnetization be saturated with a small external magnetic field. Comparative Examples 1 to 1 shown in Table 2
At 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 is 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 set to 6 kOe or less.

Further, when used as a perpendicular magnetization film, it is more preferable that the effective magnetic anisotropy energy is positive. Therefore, as shown in Examples 1 to 3 in Table 1, the composition is Co _a Pt _b Ru _c , 20 ≦ a ≦ 40, 10 ≦ b ≦ 30, 40 ≦ c ≦ 6.
It is preferable that 0 and 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 practically sufficient perpendicular magnetization characteristic in the formed film. 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 having such characteristics of the magnetic recording film forming the recording layer.

[Brief description of drawings]

FIG. 1 Composition of Examples and Comparative Examples

Claims (4)

[Claims] 1. A ternary alloy of 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 (however, a, b, and c are the composition ratio by 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 .ltoreq.30, 40.ltoreq.c.ltoreq.60 and a + b + c = 100. 3. A magnetic recording medium comprising the magnetic recording film according to claim 1 as a recording layer. 4. A magneto-optical recording medium comprising the magnetic recording film according to claim 1 as a recording layer.