JP2001026860A - Co-Pt-B BASE TARGET AND ITS PRODUCTION - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a target for forming a Co-Pt-B magnetic film formed of the stock having fine crystal grain size and to provide a method for producing it. SOLUTION: This target is composed of 10>=B>=1 at% and 30>=Pt>=5 at%, and the balance substantial Co, in which the average crystal grain size of the matrix is <=50 μm, and borides present in the structure are dispersed in layers in the case of being viewed in the cross-section of the target. Preferably, it is incorporated with 30>=Cr>=10 at%, 7>=Ta>0 at%, 30>=Ni>=5 at% and 5>=(Ti+ Zr+Hf+V+Nb+Mo+W+Cu+Ag+Au)>0 at%. Moreover, as to the target having the above compsn., by subjecting the stock composed of 10>=B>=1 at% and 30>=Pt>=5 at%, and the balance Co to hot rolling, the average crystal grain size of the matrix can be controlled to <=50 μm, and borides present in the structure can be dispersed in layers in the case of being viewed in the cross-section of the target.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a Co-Pt-B-based target used for forming a magnetic film of a magnetic recording medium for a magnetic disk drive and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, Co-based magnetic films have been developed to enable high-density magnetic recording.
And Pt additions have been made. Recently, it has been reported that the addition of B to a Co-based magnetic film significantly improves the magnetic properties. Appl. Phys. 84, 6202 (199
8). And so on.

[0003]

The present inventors have studied the Co-based magnetic film to which the above-described B is added, and have confirmed that the Co-based magnetic film to which Pt is added significantly improves the magnetic characteristics. . As a method for producing the Co—Pt—B-based magnetic film, a sputtering method or the like can be used as described in the above-mentioned literature. In the sputtering method, a target serving as a supply source of a film composition is required.

[0004] The present inventors have studied the production of a target for forming a Co-Pt-B-based magnetic film. When a Co-Pt-B-based melting / casting target is used, there is a problem that the characteristics of the manufactured magnetic film vary. The melting / casting target was formed as a somewhat fine chill crystal, a coarse and columnar crystal depending on the cooling direction, and a somewhat fine equiaxed crystal, and confirmed that the crystal grain size was large and non-uniform. Further, it was confirmed that the large and non-uniform crystal grain size was the cause of the variation in the characteristics of the magnetic film. Therefore, an object of the present invention is to provide a target material for forming a Co—Pt—B-based magnetic film, which has a fine crystal grain size and a method of manufacturing the same.

[0005]

As a result of the study, the present inventors have found that the problem that the characteristics of the magnetic film vary when a Co-Pt-B-based melting / casting target is used is due to the existence of coarse crystals. I found that I depended. Then, a means for preventing the generation of coarse crystals confirmed in the casting target was examined, and even when a Co-Pt-B material having a large amount of boride including B at 1 at% or more was found to be hot during casting. It has been found that cold rolling can be applied. The structure obtained by hot rolling enables the crystal grain size to be reduced and the boride to be dispersed, and a thin film having less variation in film characteristics such as coercive force can be obtained. Reached.

That is, the present invention relates to 10 ≧ B ≧ 1 at%,
A target mainly composed of 30 ≧ Pt ≧ 5 at%, with the balance being Co, wherein the average crystal grain size of the matrix is 50 μm or less, and the boride present in the structure is dispersed in a layered form when viewed in the cross section of the target. Co
-Pt-B type target. The present invention preferably provides 30 ≧ Cr ≧ 10 at%, 7 ≧ Ta> 0 at%, 30 ≧
Ni ≧ 5 at% and 5 ≧ (Ti + Zr + Hf + V + N
b + Mo + W + Cu + Ag + Au)> 0 at%, individually or in combination.

The manufacturing method of the present invention is a method for manufacturing a target having the above-described composition, wherein 10 ≧ B ≧ 1 at%;
30 ≥ Pt ≥ 5 at%, with the balance being mainly Co
Hot rolling, average matrix grain size of 50μ
m or less, wherein the boride existing in the structure is dispersed in a layered form when viewed from the cross section of the target. In the production method of the present invention, preferably, 30 ≧ Cr ≧
10 at%, 7 ≧ Ta> 0 at%, 30 ≧ Ni ≧ 5 at
% And 5 ≧ (Ti + Zr + Hf + V + Nb + Mo + W
+ Cu + Ag + Au)> 0 at% can be contained individually or in combination. In the production method of the present invention, particularly preferably, the temperature at the time of hot rolling is 1100 ° C or more.
Control at 800 ° C. Further, depending on the case, it is also effective to perform a heat treatment at 1100 ° C. to 800 ° C. for 1 hour or more before hot rolling.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The most important feature of the present invention is that the variation of the melting / casting target of the Co-Pt-B system containing a large amount of boride can be applied to hot rolling which has not been considered conventionally. Another object of the present invention is to make it possible to reduce the crystal grain size and disperse the boride.

According to the study by the present inventors, the structure of the molten / casting target has a structure at the time of solidification remaining on the target as it is, and has a structure in which crystal orientations are aligned in a large area such as a columnar crystal. At the time of sputtering, the manner in which the sputtered particles fly also depends on the crystal orientation.In the melting / casting target, the crystal grain size is coarse and non-uniform.
An attempt was made to reduce variations in the characteristics of the magnetic film by reducing the crystal grain size of the matrix.

The present inventor has proposed Co-Pt having poor hot workability.
By conducting hot rolling on a -B type alloy, the crystal grain size was refined, and further, boride was dispersed, and it was studied to produce a uniform material. As a result, B hardly forms a solid solution in Co, and added B almost forms a boride,
Since the formed boride is extremely fragile and extremely deteriorates hot workability, hot rolling cannot be performed at a very low temperature. Further, when B is added to the Co-based alloy, a eutectic develops around 1150 ° C., so that the temperature during hot rolling cannot be increased to a temperature higher than the eutectic temperature. For these reasons, it has been found that the hot working conditions of a Co-based alloy to which B is added, particularly a Co-based alloy to which 1 at% or more of B is added, must be strictly controlled.

The present inventor controls the working temperature during hot rolling from 1100 ° C. at which no eutectic occurs to 800 ° C., which is the minimum temperature at which hot working is possible, thereby improving hot workability. Rolling of a bad Co-Pt-B alloy was enabled. Further, by performing hot rolling under such hot rolling conditions, the average crystal grain size of the matrix described above is reduced to 50%.
It was confirmed that the microstructure could be reduced to μm or less, and that the boride existing in the structure became a new structure defined by the present invention, which was dispersed in a layered form when viewed in the cross section of the target. It has been found that such a structure almost eliminates variations in the characteristics of the magnetic film.

Further, in the present invention, the hot workability is further reduced by adding a high B content or adding Ta or the like. In such a case, 1100 before hot rolling.
By adding a heat treatment of 1 hour or more at a temperature of from 800C to 800C, the boride is divided and hot workability is improved.
It is effective for improving hot workability. The heat treatment time is long,
Higher heat treatment temperature is more effective, but 1100 ° C ~
By performing the treatment at 800 ° C. for 1 hour or more, a remarkable improvement in hot workability can be seen as cast. In the present invention,
Changing the hot rolling direction at the time of hot rolling is more preferable because the target has less anisotropy. The composition range of the target is 10 ≧ B ≧ 1 at%, 30 ≧ Pt ≧ 5 at%, the balance Co and 30 ≧ Cr ≧ 10 at%, 7 ≧ Ta> 0 at.
%, 30 ≧ Ni ≧ 5 at% and 5 ≧ (Ti + Zr + H
f + V + Nb + Mo + W + Cu + Ag + Au)> 0 at
% May be included because the respective effects do not appear unless the respective lower limit amounts are added, and the addition effect becomes larger than the addition effect when the upper limit or more is added. This will be described in detail below.

The addition of B has the effect of segregating at the grain boundaries in the film and of segregating the Pt element into the grains, and also has the effect of segregating non-magnetic elements such as Cr at the grain boundaries.
It becomes remarkable when added at at% or more. B is an element that promotes amorphization, and if added in excess of 10 at%, the crystallinity of the film is impaired and the magnetic properties of the film are deteriorated, so that 10 ≧ B ≧ 1 at%. The addition of Pt has the effect of increasing the magnetic anisotropy by forming a solid solution in Co and increasing the coercive force of the film. The addition of 5 at% or more has a remarkable effect on the increase in coercive force, and the addition of more than 30 at% significantly lowers the original properties of Co, so that 30 ≧ Pt ≧ 5 at%. .

The addition of Cr has the effect of segregating to the grain boundaries in the film and rendering the grain boundaries non-magnetic, thereby magnetically separating the ferromagnetic Co grains. The division is not sufficient, and the addition exceeding 30 at% lowers the magnetization of the film itself, so that 30 ≧ Cr ≧
It was set to 10 at%. The addition of Ta has the effect of reducing the crystal grain size of the film and the effect of segregating nonmagnetic elements such as Cr at the grain boundaries.
Since addition of more than t% is not preferable because it lowers the magnetization of the film, 7 ≧ Ta> 0 at% was set.

The addition of Ni has the effect of increasing the magnetic anisotropy by dissolving in Co and increasing the coercive force of the film. To increase the coercive force, a remarkable effect can be seen by adding 5 at% or more.
30 ≧ Ni to significantly lower the original properties of
≧ 5 at%. Ti, Zr, Hf, V, Nb, M
The addition of o, W, Cu, Ag and Au can be added as an additive element for improving the magnetic properties. These elements are effective when added in small amounts. However, if the total amount exceeds 5 at%, the magnetic properties and crystallinity of the film are significantly impaired.
(Ti + Zr + Hf + V + Nb + Mo + W + Cu + Ag
+ Au)> 0 at%.

[0016]

(Example 1) Co-10Pt-5B (at
%), Co-20Cr-10Pt-5B (at%), C
o-20Cr-10Pt-5B-1Ta (at%), C
o-20Cr-10Pt-10Ni-5B (at%),
Co-20Cr-10Pt-5B-1Ti (at%),
Co-20Cr-10Pt-5B-1Nb (at%),
Co-20Cr-10Pt-5B-1Mo (at%) and Co-20Cr-10Pt-5B-1Cu (at%)
%), And each of the ingots was hot-rolled under the conditions shown in Table 1.

[0017]

[Table 1]

However, in the hot rolling, the ingot thickness 40
From the mmt to the 8 mmt, rolling was performed after heating at the upper limit temperature shown in Table 1, and when the temperature was lowered to the lower limit temperature shown in Table 1, heating was performed again at the upper limit temperature. Also,
The rolling reduction per rolling was set to 10% or less, and rolling was performed to a predetermined thickness while changing the rolling direction. Tables 2 to 4 show the state of cracks as a result of hot rolling (cracks not generated: 、, cracks generated: x). Further, Tables 5 and 6 show that 900 ° C. × 1 h and 100
Co-10Pt-5B (a) heat-treated at 0 ° C. × 5 h
t%), Co-20Cr-10Pt-5B (at%) and Co-20Cr-10Pt-5B-1Ta (at
%) The state of cracking as a result of hot rolling of the ingot (no cracking: O, cracking: X) is shown. Table 2 to Table 4
By comparing Table 5 with Tables 5 and 6, it can be seen that the heat treatment before hot suppresses cracking during hot working and improves workability.

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

[Table 6]

Tables 7 and 8 show the average crystal grain size of the matrix of the target material obtained in Tables 2 to 6 as measured by a cutting method. Note that in Tables 7 and 8, measurements were made for those having no cracks. Further, as a microstructure to which a typical hot rolling of the target of the present invention is applied, Co-20Cr-10Pt-
The microstructure of the as-cast material after hot rolling of 5B (at%) and as-cast is shown in FIGS. 1 and 2 for Co-20Cr-10P.
The microstructure of the raw material after hot rolling of t-5B-1Ta (at%) and as cast is shown in FIGS. However, each was observed from the cross-sectional direction of the material.
From the microstructure of FIGS. 1-4, the material that has been hot rolled is
It can be seen that recrystallization occurs in the matrix and the crystal grain size is reduced, and the boride present in the structure has a layered and dispersed structure when viewed from the cross section of the target.

[0025]

[Table 7]

[0026]

[Table 8]

Example 2 Using a substrate in which a Cr underlayer was formed by sputtering on an Al substrate on which NiP plating had been applied, a substrate temperature of 150 ° C., an Ar pressure of 0.66 Pa, and a DC power of 500 W were used. Co-20Cr-10Pt-5B (at
%) Film formation was performed with a target. In order to investigate the variation in the characteristics of the magnetic film, the total film formation time was 5 hours at intervals of 1 hour to 1 hour.
Table 10 shows the measurement results of the coercive force Hc measured by using a vibrating sample magnetometer (VSM) after preparing a film-forming substrate for up to a time.
However, Table 10 shows that the coercive force of Sample 1 at one hour was 100
And expressed as relative values. Targets with different average crystal grain sizes are target materials processed and manufactured with as-cast texture, target materials as hot rolled, and heat treatment after hot rolling to grow crystal grains to increase crystal grain size. What was done was used.

For each target material, the average crystal grain size measured by the cutting method was measured. However, in the as-cast material, no crystal grain boundary was observed in the matrix in the dendrite structure, so that the crystal grain size could not be measured.
Further, Table 9 shows the state of dispersion of the boride when the cross section of the target was observed. With respect to the notation of the dispersion state, a layered structure is a structure according to FIGS. 1 and 3, and a random structure is a structure according to FIGS. From Table 10, it can be seen that a target having an as-cast structure has a large variation at the time of film formation, and a target having a fine crystal grain size of a matrix has a small characteristic variation of a magnetic film.

[0029]

[Table 9]

[0030]

[Table 10]

[0031]

According to the present invention, it is possible to stably supply a Co-Pt-B-based target in which the variation in the magnetic properties of the Co-Pt-B-based magnetic film of a magnetic recording medium such as a magnetic disk drive is suppressed. It became possible and became an indispensable technology for manufacturing magnetic recording media.

[Brief description of the drawings]

FIG. 1 shows Co representing a representative structure of a target of the present invention.
It is a microstructure micrograph of -20Cr-10Pt-5B (at%).

FIG. 2 shows Co representing a representative structure of a target of a comparative example.
It is a microstructure micrograph of -20Cr-10Pt-5B (at%).

FIG. 3 shows Co representing a representative structure of the target of the present invention.
It is a microstructure micrograph of -20Cr-10Pt-5B-1Ta (at%).

FIG. 4 shows Co representing a representative structure of a target of a comparative example.
It is a microstructure micrograph of -20Cr-10Pt-5B-1Ta (at%).

Claims (12)

[Claims] 1. At least 10 ≧ B ≧ 1 at%, 30 ≧ Pt ≧ 5a
a target mainly composed of t% and the balance Co, wherein the average crystal grain size of the matrix is 50 μm or less, and boride present in the structure is dispersed in a layered form when viewed in a cross section of the target. Co-Pt-B-based target. 2. The Co—Pt—B-based target according to claim 1, wherein the target contains 30 ≧ Cr ≧ 10 at%. 3. The Co—Pt—B-based target according to claim 1, wherein 7 ≧ Ta> 0 at% is contained. 4. The method according to claim 1, wherein the content of Co is 30 ≧ Ni ≧ 5 at%.
Pt-B target. 5. 5 ≧ (Ti + Zr + Hf + V + Nb + M
o + W + Cu + Ag + Au)> 0 at%.
Pt-B target. 6. At least 10 ≧ B ≧ 1 at%, 30 ≧ Pt ≧ 5a
t%, the balance of the material mainly composed of Co is subjected to hot rolling,
A method for producing a Co-Pt-B-based target, wherein a boride present in a structure having an average crystal grain size of a matrix of 50 µm or less is dispersed in a layer when viewed in a cross section of the target. 7. The manufacturing target is 30 ≧ Cr ≧ 10.
The method for producing a Co-Pt-B-based target according to claim 6, comprising at%. 8. The target to be manufactured is 7 ≧ Ta> 0 at.
8. The method for producing a Co—Pt—B-based target according to claim 6, wherein 9. The manufacturing target is 30 ≧ Ni ≧ 5a.
The method for producing a Co-Pt-B-based target according to any one of claims 6 to 8, comprising t%. 10. The target to be manufactured is 5 ≧ (Ti + Z)
r + Hf + V + Nb + Mo + W + Cu + Ag + Au)>
10 to 9 at%.
The method for producing a Co-Pt-B-based target according to any one of the above. 11. A hot rolling temperature of 1100 ° C. to 800 ° C.
The method for producing a Co-Pt-B-based target according to any one of claims 6 to 10, wherein 12. The production of a Co—Pt—B-based target according to claim 6, wherein heat treatment is performed at 1100 ° C. to 800 ° C. for 1 hour or more before hot rolling. Method.