U.S. patent application number 09/995567 was filed with the patent office on 2002-08-08 for co-base target and method of producing the same.
This patent application is currently assigned to HITACHI METALS, LTD.. Invention is credited to Murata, Hideo, Taniguchi, Shigeru, Ueno, Hide, Ueno, Tomonori.
Application Number | 20020106297 09/995567 |
Document ID | / |
Family ID | 18837227 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020106297 |
Kind Code |
A1 |
Ueno, Tomonori ; et
al. |
August 8, 2002 |
Co-base target and method of producing the same
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.gtoreq.Pt.gtoreq.5 at%, 30.gtoreq.Cr.gtoreq.10 at%,
10.gtoreq.Ta>0 at% and/or 30.gtoreq.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.
Inventors: |
Ueno, Tomonori; (Purchase,
NY) ; Murata, Hideo; (Saihaku-gun, JP) ;
Taniguchi, Shigeru; (Yasugi-shi, JP) ; Ueno,
Hide; (Yasugi-shi, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037-3202
US
|
Assignee: |
HITACHI METALS, LTD.
|
Family ID: |
18837227 |
Appl. No.: |
09/995567 |
Filed: |
November 29, 2001 |
Current U.S.
Class: |
419/12 ;
75/244 |
Current CPC
Class: |
C22C 19/07 20130101;
C23C 14/3414 20130101 |
Class at
Publication: |
419/12 ;
75/244 |
International
Class: |
C22C 019/07 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 1, 2000 |
JP |
2000-366639 |
Claims
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.gtoreq.Pt.gtoreq.5
atomic %, 30.gtoreq.Cr.gtoreq.10 atomic %, 10.gtoreq.Ta>0 atomic
% and/or 30.gtoreq.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.gtoreq.B>10
atomic %, 30.gtoreq.Pt.gtoreq.5 atomic %, 30.gtoreq.Cr.gtoreq.10
atomic %, 10.gtoreq.Ta>0 atomic % and/or 30.gtoreq.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.gtoreq.Pt.gtoreq.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.gtoreq.Cr.gtoreq.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.gtoreq.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.gtoreq.Ni>0 atomic %, more
preferably 30.gtoreq.Ni.gtoreq.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.degree. C. (temperature), 100 MPa
(pressure) and 3 h (time), and subsequently specimen targets each
having .phi.101.times.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.
1TABLE 1 Raw material powder composition Average Particle Oxygen
Specimen (atomic %) Size (.mu.m) (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]
2TABLE 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 *Note: O = oxygen
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.degree. C. (temperature),
100 MPa (pressure) and 3 hours (time) to produce targets of
.phi.101 (mm) (diameter) .times. 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.
3TABLE 3 Raw material powder Av. Particle Oxygen Specimen
composition (atomic %) Size (.mu.m) (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 *Note: Av. Particle
Size = Average Particle Size
[0039]
4TABLE 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 *Note: O = oxygen
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.degree. C. (temperature), 100 MPa (pressure) and
3 hours (time) to produce specimen targets having .phi.101 (mm)
(diameter) .times. 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.
5TABLE 5 Raw material powder Av. Particle Oxygen Specimen
composition (atomic %) Size (.mu.m) (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 *Note:
Av. Particle Size = Average Particle Size
[0043]
6TABLE 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--15-
B 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--15- B 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--15- B 87 Invention Ex.
53 Co--20Cr--10Pt--5Tb 201 Comparative Ex. *Note: O = oxygen; Ex. =
Example
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.degree. C..times.100 MPa.times.3 hours. The diffusion
treatment of the sintered materials were conducted under conditions
of 1100.degree. C..times.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
.phi.101.times.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.degree.
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.
7TABLE 7 Specimen Process Remarks 41 Co--20Cr--10Pt--15B (at %)
Invention Example atomized powder .fwdarw. sintering 42
Co--22.2Cr--16.7B (at %) Invention Example atomized powder + Pt
powder .fwdarw. sintering 43 Co--22.2Cr--16.7B (at %) Invention
Example atomized powder + Pt powder .fwdarw. sintering .fwdarw.
diffusion treatment 44 Co--23.5Cr--11.8Pt (at %) Comparative
Example atomized powder + B powder .fwdarw. sintering 45 Melting
and casting Comparative Example *Note: at % = atomic %
[0048]
8 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 *Note: O = oxygen
[0049]
9 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
*Note: FMT = Film Forming Time
[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.
* * * * *