JP2000207725A - MAGNETIC RECORDING MEDIUM AND CoTa ALLOY TARGET - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium and a target suitable for high density recording by improving the magnetic characteristics of a Co based magnetic layer. SOLUTION: Base layers in at least one or more layers are adhered between a non-magnetic substrate and a Co based magnetic layer in this magnetic recording medium, and at least one layer of the base layers is formed of CoTa based alloy in which Ta content is 30-65 at.% and the remainder has Co as the main component. It is preferable that the Ta amount is 45-55 at.%. The target is formed as a CoTa based alloy target being a powder sintered body in which Ta amount is 30-65 at.% and the remainder has Co as the main component, and it is preferable that no metallic Co phase exists substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic recording medium for a magnetic disk drive or the like and a CoTa-based target used for the same.

[0002]

2. Description of the Related Art Conventionally, Co-based magnetic layers have been developed so as to enable high-density magnetic recording. As one of the means, epitaxial growth is used for forming a magnetic layer. In order to epitaxially grow a magnetic layer, the lattice constant, crystal orientation, and film uniformity of an underlayer have been improved. For example, the Co-based magnetic layer has a hexagonal close-packed structure, and is well-matched to the C-axis lattice constant of the Co-based magnetic layer in order to epitaxially grow so that the easy magnetization direction, that is, the C-axis direction is in-plane. Pure Cr and Cr alloys are the mainstream.

Recently, European Patent Publication EP07 / 07
04839A reports that a magnetic recording medium with high coercive force and low noise can be obtained by employing a structure using an intermetallic compound having a B2 structure as an underlayer. Especially Co
If a fine B2 structure intermetallic compound layer is formed as a further lower layer of the Cr-based underlayer having good compatibility with the system-based magnetic layer, the Cr-based layer serving as the underlayer can be epitaxially grown. A fine Cr-based underlayer can be formed. As a result, the overlying magnetic layer can also undergo epitaxial growth reflecting the fine state of the underlying layer, resulting in high coercive force and low noise.

[0004]

The present inventor has studied an underlayer of an intermetallic compound having a B2 structure typified by NiAl, and found that the layer of the intermetallic compound having a B2 structure is pure Cr used as an underlayer. It was confirmed that the compatibility with the layer, the Cr alloy layer and the Co-based magnetic layer was good. But,
With the recent increase in the recording density of magnetic disks, means for achieving a higher recording density have been demanded.

[0005] Further, the film forming apparatus for magnetic disks has shifted from the conventional in-line type to the single-wafer type. In a single-wafer apparatus, a simple clip method is adopted instead of the conventional bonding method because the frequency of target replacement increases. Further, the film forming speed has been increased to improve productivity, and the power input to the target has been increased. Since a large thermal stress is generated in a target during film formation due to a decrease in cooling capacity and an increase in input power due to the clipping method, a high-strength target capable of withstanding the thermal stress is required. The purpose of the present invention is
An object of the present invention is to provide a magnetic recording medium and a CoTa-based alloy target suitable for high-density recording by improving the magnetic characteristics of a Co-based magnetic layer.

[0006]

The present inventors have studied the underlayer and the seed layer in order to increase the recording density of the magnetic layer.
It has been found that a magnetic recording medium having excellent magnetic properties can be obtained by using a CoTa-based alloy having a Ta content of 30 to 65 at% and a balance of Co as a main component as an underlayer.

That is, according to the present invention, in a magnetic recording medium having at least one underlayer adhered between a nonmagnetic substrate and a Co-based magnetic layer, at least one of the underlayers has a Ta content. Is a CoTa-based alloy whose main component is 30 to 65 at%, with the balance being Co. Preferably, the amount of Ta is 45 to 55 at%.
It is.

Further, the present inventor has found that the Ta amount is 30-65a.
Investigate a target with high bending strength suitable for forming a CoTa-based alloy underlayer mainly composed of t% and the balance Co, and obtain a target with high bending strength by using the powder sintering method. Was found. That is, the target of the present invention is a CoTa-based alloy target characterized in that it is a powder sintered body mainly composed of a powder having a Ta content of 30 to 65 at% and the balance Co.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, an important feature of the present invention is that the underlayer is made of a CoTa-based alloy film having a Ta content of 30 to 65 at% and the balance being Co. Has been improved.

FIG. 1 reports Barabash et al.
M. Barabash, et al. : Crystal
structure of Metals and A
lloys, 1986, p247) Co-Ta
Figure 2 shows a binary phase diagram. Co-Ta binary system is made of various metals
Intermediate compounds are formed. Of these intermetallic compounds,
D8₅Co with structure₆Ta₇(Μ) phase and C15 structure
Co with structure₂Ta (λ ₂) When the phase is formed on the substrate
A fine film can be obtained.
Be improved. In particular, D8₅Co with structure₆Ta₇(Μ)
When the phase is used as the underlayer, the magnetic properties are significantly improved. T
a is D8₅Co with structure₆Ta₇(Μ) phase and C
Co with 15 structure ₂Ta (λ₂30) Phase stable
5 at% is preferable, and D8₅Co with structure ₆Ta
₇45 to 55 at%, in which the solid solution of the (μ) phase is stable,
preferable.

Further, by adding an additional element, it becomes possible to further reduce the crystal grain size of the film and to give lattice distortion. However, _Co 6 with a D8 ₅ structure Ta
Co ₂ Ta (λ ₂ ) having ₇ (μ) phase and C15 structure
It can be added within a range where the phase is stable, and the total amount of added elements is preferably 10 at% or less. Elements that promote miniaturization include B, C, N, O, Al, Si, Ti, Zr, and Hf.
And V, N
b, Cr, Mo, W, Mn, Fe, Ni and the like.

In the case of a CoTa-based alloy target having a Ta content of 30 to 65 at% and a balance of Co as a main component, a powder sintering method is preferable to a powder sintering method in consideration of the target strength. Furthermore, if Co is present as a metal phase in the target, the target has magnetism and the use efficiency is deteriorated. Therefore, it is preferable that the metal Co phase does not remain in the target. Using the raw material powder in which the metal Co remains,
Co and T by diffusion during sintering or diffusion by heat treatment after sintering
Although a can be an intermetallic compound, it is preferable that an alloy powder composed of an intermetallic compound of Co and Ta be used as a raw material powder as a Co supply source. Examples of a method for producing an alloy powder composed of an intermetallic compound include a method of pulverizing a molten / cast ingot, an atomizing method, and a reaction synthesis method.

When adding an additive element, it is possible to add a pure metal powder and an alloy powder, but when adding a ferromagnetic element such as Fe or Ni, a single powder is added. However, it is preferable to add it to the alloy powder because the magnetism as a target is reduced.

[0014]

(Example 1) Co-, Ta-, Ti-, Zr-, Cr-, Mo-, W-, Nb-, B-, Al-, Ni- and Fe-powder 30at% Ta, Co-40at% Ta, C
o-50at% Ta, Co-60at% Ta, Co-4
9at% Ta-2at% Ti, Co-49at% Ta-
2 at% Zr, Co-49 at% Ta-2 at% Cr,
Co-49at% Ta-2at% Mo, Co-49at
% Ta-2at% W, Co-49at% Ta-2at%
Nb, Co-49at% Ta-2at% B, Co-49
at% Ta-2at% Al, Co-49at% Ta-2
at% Ni and Co-49at% Ta-2at% Fe
The powder was mixed at 1200 ° C. for 3 hours for 10 hours.
The target was produced by sintering under the condition of 0 MPa.

[0015] A substrate temperature of 150 ° C, an Ar pressure of 0.66 Pa,
Film formation was performed under the conditions of DC power of 500 W with the layer configuration shown in Table 1. Table 2 shows the measurement results of the coercive force squareness ratio S ^* (= Hc '/ Hc) for evaluating the coercive force Hc and noise of each substrate measured by a VSM (vibrating sample magnetometer). Here, Hc ′ is H at the intersection of the tangent at the point Hc and the perpendicular at the point of the residual magnetization Mr in the magnetic hysteresis curve. As described above, it can be seen that the characteristics of the magnetic recording medium are improved by using the CoTa alloy for the underlayer.

[0016]

[Table 1]

[0017]

[Table 2]

Example 2 A target prepared by sintering Co-50 at% Ta atomized powder at 1200 ° C. for 3 hours under the conditions of 100 MPa so that the Co powder and the Ta powder become Co-50 at% Ta. Mix powder 12
Target manufactured by sintering at 100 ° C. for 3 hours at 00 ° C., Co-5 manufactured by melting and casting method
Table 3 shows the bending strength of the 0 at% Ta target. However, the transverse rupture strength was measured using a 70 × 5 × 5 (mm) test piece.
This was performed by a three-point bending test with a span distance of 50 (mm). In addition, when each of the targets of φ101 × 4t (mm) was formed under the conditions of an Ar pressure of 0.66 Pa and a DC power of 500 W, the time until the target life was Co-50.
Atomized powder of at% Ta was prepared at 1200 ° C. for 3 hours.
Table 3 shows a target prepared by sintering under the condition of 100 MPa.

Further, a substrate temperature of 150 ° C. and an Ar pressure of 0.6 were placed on the Ni—P plated Al and glass substrates.
Film formation was performed under the conditions of 6 Pa and a DC power of 500 W with the layer configuration shown in Table 4. Table 5 shows the measurement results of the coercive force squareness ratio S ^* (= Hc '/ Hc) for evaluating the coercive force Hc and noise of each substrate measured by a VSM (vibrating sample magnetometer). Here, Hc ′ is H at the intersection of the tangent at the point Hc and the perpendicular at the point of the residual magnetization Mr in the magnetic hysteresis curve. It can be seen that the target produced by the powder sintering method has high bending strength, and the life of the alloy target using the atomized powder that has been alloyed in advance is long.

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

According to the present invention, in a magnetic recording medium in which at least one or more underlayers are adhered between a nonmagnetic substrate and a Co-based magnetic layer, the amount of Ta as an underlayer is from 30 to 30.
By using a CoTa-based alloy mainly composed of 65 at% and the balance Co, the magnetic properties can be improved.
aT is 30 to 65 at%, CoT mainly composed of the balance Co
The powder sintering target of the high bending strength of the a-based alloy has become an indispensable technology for magnetic recording media.

[Brief description of the drawings]

FIG. 1 is a Co-Ta binary phase diagram.

Claims (2)

[Claims] In a magnetic recording medium having at least one underlayer adhered between a nonmagnetic substrate and a Co-based magnetic layer, at least one of the underlayers has a Ta amount of 30 to 65 at. %, The balance being a CoTa-based alloy mainly composed of Co. 2. A CoTa powder characterized in that it is a powder sintered body having a Ta amount of 30 to 65 at% and a balance of Co as a main component.
Series alloy target.