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Publication numberUS20020106297 A1
Publication typeApplication
Application numberUS 09/995,567
Publication dateAug 8, 2002
Filing dateNov 29, 2001
Priority dateDec 1, 2000
Publication number09995567, 995567, US 2002/0106297 A1, US 2002/106297 A1, US 20020106297 A1, US 20020106297A1, US 2002106297 A1, US 2002106297A1, US-A1-20020106297, US-A1-2002106297, US2002/0106297A1, US2002/106297A1, US20020106297 A1, US20020106297A1, US2002106297 A1, US2002106297A1
InventorsTomonori Ueno, Hideo Murata, Shigeru Taniguchi, Hide Ueno
Original AssigneeHitachi Metals, Ltd.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Co-base target and method of producing the same
US 20020106297 A1
Abstract
The invention relates to a Co-base target made of a sintered powder, having a restrained amount of oxygen, and a producing method thereof. The target contains from more than 10 to not more than 25 at % of B and not more than 100 ppm of oxygen. It may contain 30≧Pt≧5 at%, 30≧Cr≧10 at%, 10≧Ta>0 at% and/or 30≧Ni>0 at%. It may contain also from more than 0 (zero) to not more than 15 at% in total of one or more elements selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and rare earth elements. The target is produced by melting a Co-base alloy together with an additive B in an amount of from more than 10 to not more than 25 at% whereby deoxidizing, rapidly cooling the molten metal to produce an alloy powder and sintering the alloy powder. It can be optionally produced by mixing the above alloy powder with another metal powder, more particularly consisting of one or more elements selected from the group consisting of Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and Pt, and sintering the powder mixture.
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Claims(28)
What is claimed is:
1. A Co-base target produced by powder sintering, which comprises from more than 10 atomic % to 25 atomic % of B (boron) and not more than 100 ppm of oxygen as an impurity.
2. A Co-base target according to claim 1, which further comprises from more than zero to 10 atomic % Ta.
3. A Co-base target according to claim 1, which further comprises from more than zero to 30 atomic % Ni.
4. A Co-base target according to claim 1, which further comprises from more than zero to 10 atomic % Ta and from more than zero to 30 atomic % Ni.
5. A Co-base target according to claim 1, which further comprises from more than zero to 15 atomic % in a total amount of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and REM.
6. A Co-base target according to claim 5, which further comprises from more than zero to 10 atomic % Ta.
7. A Co-base target according to claim 5, which further comprises from more than zero to 30 atomic % Ni.
8. A Co-base target according to claim 5, which further comprises from more than zero to 10 atomic % Ta and from more than zero to 30 atomic % Ni.
9. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
10. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 10 atomic % Ta, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
11. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 30 atomic % Ni, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
12. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 10 atomic % Ta, from more than zero to 30 atomic % Ni, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
13. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 15 atomic % in a total amount of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and REM, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
14. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 10 atomic % Ta, from more than zero to 15 atomic % in a total amount of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and REM, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
15. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 30 atomic % Ni, from more than zero to 15 atomic % in a total amount of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and REM, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
16. A Co-base target produced by powder sintering, which consists essentially of from more than 10 atomic % to 25 atomic % of B (boron), 5 to 30 atomic % Pt, 10 to 30 atomic % Cr, from more than zero to 10 atomic % Ta, from more than zero to 30 atomic % Ni, from more than zero to 15 atomic % in a total amount of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and REM, not more than 100 ppm of oxygen as an impurity and the balance mainly of Co.
17. A method of producing a Co-base target, which comprises:
melting a Co-base alloy and an additive B (boron), whereby deoxidizing the Co-base alloy,
subjecting the resultant Co-base alloy to a rapid cooling treatment to obtain a powder of the Co-base alloy, and
sintering the thus obtained alloy powder.
18. A method of producing a Co-base target, which comprises:
melting a Co-base alloy and an additive B (boron), whereby deoxidizing the Co-base alloy,
subjecting the resultant Co-base alloy to a rapid cooling treatment to obtain a powder of the Co-base alloy,
mixing the Co-base alloy powder and another metal powder, and
sintering the thus obtained mixed powder.
19. A method of producing a Co-base target, which comprises:
melting a Co-base alloy and an additive B (boron), whereby deoxidizing the Co-base alloy,
subjecting the resultant Co-base alloy to a rapid cooling treatment to obtain a powder of the Co-base alloy,
mixing the Co-base alloy powder and a metal
powder of at least one element selected from the group consisting of Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and Pt, and
sintering the thus obtained mixed powder.
20. A method of producing a Co-base target according to claim 17, 18, 19, which comprises:
melting a Co-base alloy and an additive B (boron) in an amount of from more than 10 atomic % to 25 atomic %, whereby deoxidizing the Co-base alloy.
21. A method according to claim 18, wherein the thus obtained sintered product is subjected to a heat treatment.
22. A method according to claim 19, wherein the thus obtained sintered product is subjected to a heat treatment.
23. A method according to claim 17, wherein the rapid cooling treatment is conducted by the atomizing process.
24. A method according to claim 18, wherein the rapid cooling treatment is conducted by the atomizing process.
25. A method according to claim 19, wherein the rapid cooling treatment is conducted by the atomizing process.
26. A method according to claim 17, wherein the sintering is conducted by the Hot Isostatic Pressing method.
27. A method according to claim 18, wherein the sintering is conducted by the Hot Isostatic Pressing method.
28. A method according to claim 19, wherein the sintering is conducted by the Hot Isostatic Pressing method.
Description
BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a Co-base target which is used to form a magnetic film of a magnetic recording medium for a magnetic disk device, etc., and a method of producing the Co-base target.

[0003] 2. Description of the Prior Art

[0004] Heretofore, a Co-base magnetic film has been developed so as to enable high density magnetic recording, and the addition of Pt and the like to the Co-base magnetic film has been performed. Such a Co-base magnetic film is usually formed by spattering. Furthermore, as disclosed in JP-B2-2806228, etc., a target produced by a melting/casting method has usually been used for this spattering.

[0005] In order to obtain the Co-base magnetic film, a target produced by powder sintering has been also proposed as disclosed in, for example, JP-A-3-138365.

[0006] In order to meet a recent request of a magnetic film having a high magnetic coercive force, it is necessary to contain a large amount of Pt, Cr, Ta and the like in addition to Co. In the case of the melting/casting process, as an amount of additive alloying elements increases, there arise problems of component segregation during casting and a difficulty in equalizing the metal structure of a cast material by plastic working. On the other hand, in the case of the powder-metallurgical method, there is an advantage that a metal structure in which the additive elements are uniformly dispersed can be obtained.

[0007] Further, there has been known a powder-metallurgical process according to which an elemental B (boron) is used in order to improve magnetic properties a sintered material, as disclosed in JP-A-5-263230.

[0008] However, a primary demerit of the powder-metallurgical method is that, since a material is processed in a powdery state, a much amount of oxygen is inevitably contained in the powdery material as compared to a cast material. From the viewpoint that the amount of oxygen should be reduced as much as possible rather than solving the problem of a non-uniform composition due to the component segregation since oxygen adversely affects on magnetic recording properties of the material, the powder-metallurgical method has not yet been used in a large scale.

SUMMARY OF THE INVENTION

[0009] An object of the present invention is to provide a novel Co-base target in which there can be inhibited an increase in the amount of oxygen which is the disadvantage of a powder sintering material capable of obtaining a uniform composition, and a method of producing the Co-base target.

[0010] The present inventors found that it is possible to produce a sintered target containing a low amount of oxygen by making the most of a deoxidizing effect of additive B (boron), whereby the present invention has been achieved.

[0011] More particularly, a novel target of the present invention is a Co-base target produced by powder sintering which comprises from more than 10 atomic % to 25 atomic % of B and not more than 100 ppm of oxygen.

[0012] Preferably, the target may comprise 30≧Pt≧5 atomic %, 30≧Cr≧10 atomic %, 10≧Ta>0 atomic % and/or 30≧Ni>0 atomic %. More preferably, the target may comprise from more than 0 (zero) to not more than 15 atomic % in total of one or more elements selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and rare earth elements (REM).

[0013] The invention target can be obtained by a method of producing a Co-base target comprising the steps of melting a Co-base alloy together with an additive B (boron) in an amount of more than 10 to not more than 25 atomic % whereby deoxidizing the Co-base alloy, subjecting the resultant Co-base alloy to a rapid cooling treatment to obtain a powder, and sintering the resultant powder mixture to form a target of a sintered powder.

[0014] Alternatively, the invention target can be obtained by a method of producing a Co-base target comprising the steps of melting a Co-base alloy together with an additive B (boron) in an amount of more than 10 to not more than 25 atomic % whereby deoxidizing the Co-base alloy, subjecting the resultant Co-base alloy to a rapid cooling treatment to obtain a powder, mixing the powder with another metal powder, more particularly a metal powder consisting of one or more elements selected from the group consisting of Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and Pt, and sintering the resultant powder mixture to form a target of a sintered powder.

DESCRIPTION OF EMBODIMENTS

[0015] The key feature of the invention is that not more than 100 ppm of oxygen in the Co-base target produced by powder sintering has been realized which cannot be considered otherwise in the past. By virtue of the appropriate amount of B (boron), it has been possible to realize the invention target which is produced by powder sintering and contains a low amount of oxygen.

[0016] Since B (boron) has a high affinity with oxygen and a boron oxide is liable to sublimate, it is added to a molten metal when producing the powder by rapid cooling or when forming a master ingot (base alloy) to deoxidize the same with B in advance, whereby the oxygen amount of the powder produced by rapid cooling from a melt can be remarkably reduced.

[0017] In the present invention, it is preferable to sinter the powder obtained by rapid cooling and adjusted to have a desired target composition. Alternatively, in the case where the Co-base target material comprises an expensive additive such as Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and Pt, it is possible to mix the powder containing an additive alloying element of B (boron) obtained by rapid cooling with another metal powder consisting of one or more elements selected from the group consisting of Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and Pt, and to sinter the powder mixture. In the latter case, it is possible to optionally subject the sintered product to heat treatment or hot working in order to equalize the metal structure.

[0018] While there are an atomizing method, a spin melting method and so on, which are of producing a rapidly cooled powder, it is preferable to produce the powder by the gas atomizing method from the viewpoints of a packing density and a yield of the powder.

[0019] Furthermore, the sintering method includes a hot pressing method and a Hot Isostatic Pressing method (hereinafter referred to as HIP), but the HIP to which a high pressure can be applied is preferable from the viewpoint of a density of the sintered powder.

[0020] A preferable composition of the invention target may comprise an element(s) which can improve properties of the target material as a magnetic recording film. More particularly, the target material may comprise the elements of 25≧B>10 atomic %, 30≧Pt≧5 atomic %, 30≧Cr≧10 atomic %, 10≧Ta>0 atomic % and/or 30≧Ni>0 atomic %. It may be also comprise from more than 0 (zero) to not more than 15 atomic % in total of one or more elements selected from the group consisting of Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and rare earth elements. Needless to say, the invention target material is not limited to the above compositions.

[0021] Herein below there will be described effects of the additive alloying elements.

[0022] Additive B is the most important element of the present invention.

[0023] A spatter film produced by using a Co-base target of the invention is used as a magnetic layer of a magnetic recording medium in many cases. Conventionally, the magnetic layer in the magnetic recording medium has been formed with a single layer, and the magnetic layer has had to possess all properties such as a high coercive force and a high magnetic squareness ratio. For this reason, a Co-base film containing more than 10% of B as in the present invention has not been considered, because an increase of the coercive force cannot be expected.

[0024] However, at the present time, the magnetic layer consists of a plurality of layers. Thus, the magnetic layer has been modified so that different properties are required for the layers, respectively.

[0025] In the spatter film made of the Co-base target to which more than 10 atomic % of B is added as in the present invention, the increase in the coercive force cannot be desired as stated above, but the effect of reducing the noise of the spatter film is substantial. Moreover, when more than 10 to not more than 25 atomic % of B is added, the spatter film can possess an excellent effect of reducing oxygen.

[0026] However, the upper limit of the additive B is set to not more than 25 atomic % of B, because there noticeably appears an adverse influence that the spatter film becomes amorphous, if more than 25 atomic % of B is added. The oxygen reducing effect according to the invention can be attained by more than 10 atomic % of additive B (boron), which is preferable in order to obtain a target material containing not more than 100 ppm oxygen.

[0027] Pt can be added, since it increases the magnetic anisotropy by dissolving into Co and is effective to increase the coercive force of the film. Preferably, not less than 5 atomic % Pt is added in order to clearly increase the coercive force of the film. Further, since more than 30 atomic % of additive Pt remarkably deteriorates the inherent magnetic properties of Co, preferably Pt is added in an amount of 30≧Pt≧5 atomic %.

[0028] Cr segregates at grain boundaries in the film to make the grain boundaries non-magnetic whereby magnetically dividing ferromagnetic Co grains. When Cr is added in an amount of less than 10 atomic %, the magnetic division is not sufficient. On the other hand, when Cr is added in an amount of more than 30 atomic %, the magnetization of the film itself is deteriorated. Therefore, preferably Cr is added in an amount of 30≧Cr≧10 atomic %.

[0029] Ta has effects of refining crystal grains of the film and causing non-magnetic elements such as Cr to segregate at the grain boundaries. Such effects can be observed even if an additive Ta is small. On the other hand, it is not preferable to add an additive more than 10 atomic % of Ta because the magnetization of the film is deteriorated. Therefore, preferably Ta is added in an amount of 10≧Ta>0 atomic %.

[0030] Ni dissolves into Co to improve the magnetic anisotropy and the coercive force of the film. Ni can be added in an amount of not more than 30 atomic %. In order to increase the coercive force, Ni is added in an amount of not less than 5 atomic %, whereby a remarkable effect can be observed. An excess amount of more than 30 atomic % of Ni deteriorates inherent characteristics of Co. Thus, a preferable amount of Ni is 30≧Ni>0 atomic %, more preferably 30≧Ni≧5 atomic %.

[0031] Ti, Zr, Hf, V, Nb, Mo, W, Cu, Ag, Au, Ru, Rh, Pd, Os, Ir and rare earth elements (REM) are an element group having a common effect of improving magnetic properties of the film. Ti, Zr, Hf and rare earth elements have an effect of refining the crystal grains of the film; V and Nb have a similar effect to that of Ta; Mo and W have a similar effect to that of Cr; Cu, Ag and Au have an effect of dividing Co grains by virtue of segregation thereof at grain boundaries of the material; and Ru, Rh, Pd, Os and Ir have a similar effect to that of Pt. These elements are effective even if an additive amount thereof is small. When the total amount of the elements is more than 15 atomic %, the magnetic properties and crystallizing property of the film are deteriorated. Therefore, a total amount of them is preferably from more than zero to not more than 15 atomic %.

EXAMPLES Example 1

[0032] Castings of some Co-base mother alloys were produced, wherein B (boron) was added during vacuum melting of the alloys in order to deoxidize the respective melt. The thus produced mother alloys were subjected to the gas atomization process to produce specimen powders of the invention examples. The chemical compositions of the powders are shown in Table 1. It is noted that the gas atomization was carried out in an Ar atmosphere. An average particle size and an oxygen amount of the respective atomized powders is shown in Table 1. It is noted that Specimens 5 and 10 of comparative examples shown in Table 1 were produced by the same process as those of the above invention examples except for not using additive B (boron) effective for deoxidization.

[0033] The thus produced atomized powders were sintered by the HIP method under conditions of 1000° C. (temperature), 100 MPa (pressure) and 3 h (time), and subsequently specimen targets each having φ101×5t (mm) (thickness) were produced by machining. Oxygen analysis values of the specimen targets are shown in Table 2.

[0034] As shown in Table 2, it can be understood that the specimen targets, each produced by sintering the atomized powder deoxidized by adding boron during melting, contain low amounts, especially not more than 100 ppm, of oxygen.

TABLE 1
Raw material powder
composition Average Particle Oxygen
Specimen (atomic %) Size (μm) (ppm)
1 Co—20Cr—10Pt—11B 45 36
2 Co—20Cr—10Pt—15B 42 34
3 Co—20Cr—10Pt—20B 40 32
4 Co—20Cr—10Pt—25B 38 30
5 Co—20Cr—10Pt 113 118
6 Co—20Cr—10Pt—2Ta—11B 40 39
7 Co—20Cr—10Pt—2Ta—15B 38 38
8 Co—20Cr—10Pt—2Ta—20B 37 37
9 Co—20Cr—10Pt—2Ta—25B 35 33
10 Co—20Cr—10Pt—2Ta 101 175

[0035]

TABLE 2
Target composition O*
Specimen (atomic %) (ppm) Remarks
1 Co—20Cr—10Pt—11B 38 Invention Example
2 Co—20Cr—10Pt—15B 37 Invention Example
3 Co—20Cr—10Pt—20B 35 Invention Example
4 Co—20Cr—10Pt—25B 33 Invention Example
5 Co—20Cr—10Pt 124 Comparative
Example
6 Co—20Cr—10Pt—2Ta—11B 42 Invention Example
7 Co—20Cr—10Pt—2Ta—15B 41 Invention Example
8 Co—20Cr—10Pt—2Ta—20B 40 Invention Example
9 Co—20Cr—10Pt—2Ta—25B 37 Invention Example
10 Co—20Cr—10Pt—2Ta 179 Comparative
Example

Example 2

[0036] Gas atomized powders having chemical compositions shown in Table 3 were produced by the same manner as in Example 1, wherein the gas atomizing was carried out in an Ar atmosphere. An average particle size and an oxygen amount of the respective atomized powders produced is shown in Table 3. Furthermore, the average particle size and an oxygen amount of a Pt powder used is also shown in Table 3.

[0037] The Pt powder shown in Table 3 was added to the respective atomized powder produced, and they were mixed and sintered by the HIP method under the conditions of 1000° C. (temperature), 100 MPa (pressure) and 3 hours (time) to produce targets of φ101 (mm) (diameter) × 5 (mm) (thickness) having compositions shown in Table 4. Oxygen analysis values of the produced targets are shown in Table 4.

[0038] As shown in Table 4, it can be understood that the targets, produced by mixing the atomized powder deoxidized by adding boron during melting with a Pt powder, and sintering the powder mixture, contain low amounts, especially not more than 100 ppm, of oxygen.

TABLE 3
Raw material powder Av. Particle Oxygen
Specimen composition (atomic %) Size (μm) (ppm)
21 Co—22.2Cr—22.2B 35 30
22 Co—22.2Cr—27.8B 32 28
23 Co—22.2Cr 115 114
24 Co—22.2Cr—2.2Ta—22.2B 37 36
25 Co—22.2Cr—2.2Ta—27.8B 35 33
26 Co—22.2Cr—2.2Ta 97 171
27 Pure Pt 131 134

[0039]

TABLE 4
Target composition O*
Specimen (atomic %) (ppm) Remarks
21 Co—20Cr—10Pt—20B 52 Invention Example
22 Co—20Cr—10Pt—25B 49 Invention Example
23 Co—20Cr—10Pt 136 Comparative
Example
24 Co—20Cr—10Pt—2Ta—20B 56 Invention Example
25 Co—20Cr—10Pt—2Ta—25B 55 Invention Example
26 Co—20Cr—10Pt—2Ta 193 Comparative
Example

Example 3

[0040] Gas atomized powders having chemical compositions shown in Table 5 were produced by the same manner as in Example 1, wherein the gas atomizing was carried out in an Ar atmosphere. An average particle size and an oxygen amount of the respective specimen atomized powders is shown in Table 5.

[0041] The atomized powders were sintered by the HIP method under conditions of 1000° C. (temperature), 100 MPa (pressure) and 3 hours (time) to produce specimen targets having φ101 (mm) (diameter) × 5 (mm) (thickness). Oxygen analysis values of the produced targets are shown in Table 6.

[0042] As shown in Table 6, it can be understood that the specimen targets, produced by sintering the atomized powder deoxidized by adding boron during melting, contain reduced amounts, especially not more than 100 ppm, of oxygen.

TABLE 5
Raw material powder Av. Particle Oxygen
Specimen composition (atomic %) Size (μm) (ppm)
31 Co—20Cr—10Pt—10Ni—15B 45 42
32 Co—20Cr—10Pt—10Ni 96 125
33 Co—20Cr—10Pt—5Ti—15B 41 51
34 Co—20Cr—10Pt—5Ti 89 143
35 Co—20Cr—10Pt—5Nb—15B 41 59
36 Co—20Cr—10Pt—5Nb 90 155
37 Co—20Cr—10Pt—5Mo—15B 51 45
38 Co—20Cr—10Pt—5Mo 108 130
39 Co—20Cr—10Pt—5Cu—15B 56 42
40 Co—20Cr—10Pt—5Cu 114 130
50 Co—20Cr—10Pt—5Ru—15B 53 47
51 Co—20Cr—10Pt—5Ru 111 133
52 Co—20Cr—10Pt—5Tb—15B 39 78
53 Co—20Cr—10Pt—5Tb 77 192

[0043]

TABLE 6
Target composition O*
Specimen (at %) (ppm) Remarks
31 Co—20Cr—10Pt—10Ni—15B 50 Invention Ex.
32 Co—20Cr—10Pt—10Ni 135 Comparative Ex.
33 Co—20Cr—10Pt—5Ti—15B 58 Invention Ex.
34 Co—20Cr—10Pt—5Ti 149 Comparative Ex.
35 Co—20Cr—10Pt—5Nb—15B 63 Invention Ex.
36 Co—20Cr—10Pt—5Nb 156 Comparative Ex.
37 Co—20Cr—10Pt—5Mo—15B 51 Invention Ex.
38 Co—20Cr—10Pt—5Mo 137 Comparative Ex.
39 Co—20Cr—10Pt—5Cu—15B 48 Invention Ex.
40 Co—20Cr—10Pt—5Cu 136 Comparative Ex.
50 Co—20Cr—10Pt—5Ru—15B 52 Invention Ex.
51 Co—20Cr—10Pt—5Ru 137 Comparative Ex.
52 Co—20Cr—10Pt—5Tb—15B 87 Invention Ex.
53 Co—20Cr—10Pt—5Tb 201 Comparative Ex.

Example 4

[0044] Specimen targets of Co-20Cr-10Pt-15B (at %) were produced by the producing processes shown in Table 7. Analysis values of impurity oxygen of the specimen targets are shown in Table 8.

[0045] Atomized powders were produced by the same method as in Examples 1 and 2. The sintering was conducted under conditions of 1000° C.×100 MPa×3 hours. The diffusion treatment of the sintered materials were conducted under conditions of 1100° C.×10 hours. The molten/cast material was obtained by melting under vacuum in an induction heating furnace and subsequently casting into a mold, whereby a specimen target of φ101×5t (mm) (thickness) was produced.

[0046] A board, wherein a Cr primer film was formed by spattering on an NiP plated Al board, was used, and the film was formed on the board with the Co-20Cr-10Pt-15B (at %) target of different production methods shown in Table 7 under conditions of 150° C. for the board temperature, 0.66 Pa for Ar pressure and 500 W DC for electric power. To investigate variations of the characteristics of magnetic film, a board formed with film was produced during a total forming time of 5 hours with one hour interval. Results of measurement of coercive force Hc measured by VSM (vibrating sample type magnetometer) are shown in Table 9, provided that Table 9 shows relative values taking the coercive force for one hour of Specimen 41 as 100.

[0047] It can be understood from Table 9 that, with regard to the respective invention specimen targets, the variation of forming film is small, that the higher the oxygen content of the specimen target is the lower the coercive force is, and that the variation of the melting/casting specimen target as time passes is slightly larger than those of the invention specimen targets.

TABLE 7
Specimen Process Remarks
41 Co—20Cr—10Pt—15B (at %) Invention Example
atomized powder → sintering
42 Co—22.2Cr—16.7B (at %) Invention Example
atomized powder + Pt
powder → sintering
43 Co—22.2Cr—16.7B (at %) Invention Example
atomized powder + Pt
powder → sintering → diffusion
treatment
44 Co—23.5Cr—11.8Pt (at %) Comparative Example
atomized powder + B
powder → sintering
45 Melting and casting Comparative Example

[0048]

TABLE 8
Specimen O* (ppm) Remarks
41 36 Invention Example
42 53 Invention Example
43 53 Invention Example
44 185 Comparative Example
45 25 Comparative Example

[0049]

TABLE 9
Coercive force (Hc)
FMT FMT FMT FMT FMT
Specimen 1 hour 2 hours 3 hours 4 hours 5 hours
41 100 100 100 101 100
42 101 99 102 100 99
43 100 100 99 99 100
44 88 95 90 98 90
45 101 100 104 99 103

[0050] According to the invention, it is possible to stably supply the Co-base target, having a uniform composition and a low oxygen amount, which can be used to produce a Co-base magnetic film for a magnetic recording medium for use in a magnetic disk device and the like. Thus, the invention is indispensable to manufacturing magnetic recording mediums.

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Classifications
U.S. Classification419/12, 75/244
International ClassificationC22C19/07, C23C14/34
Cooperative ClassificationC22C19/07, C23C14/3414
European ClassificationC22C19/07, C23C14/34B2
Legal Events
DateCodeEventDescription
Nov 29, 2001ASAssignment
Owner name: HITACHI METALS LTD., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:UENO, TOMONORI;MURATA, HIDEO;TANIGUCHI, SHIGERU;AND OTHERS;REEL/FRAME:012337/0162
Effective date: 20011019