JP2008240012A - Sputtering target for vertical magnetic recording medium film formation having high leakage magnetic flux density - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering target for vertical magnetic recording medium film formation having high leakage magnetic flux density for forming a magnetic recording film applied to a high density magnetic recording medium of a hard disk, particularly for forming a magnetic recording film applied to a vertical magnetic recording medium. <P>SOLUTION: Disclosed is a sputtering target for vertical magnetic recording medium film formation having high leakage magnetic flux density which has a chemical composition comprising a nonmagnetic oxide of 2 to 15 mol%, Cr of 3 to 20 mol%, Pt of 5 to 30 mol%, and the balance consisting of Co with unavoidable impurities and has an in-plane specific magnetic permeability of ≤50 which is lower than the thickness-wise specific permeability. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density for forming a magnetic recording film applied to a high-density magnetic recording medium of a hard disk, particularly a magnetic recording film applied to a perpendicular magnetic recording medium. It is about.

Hard disk devices are generally used as external recording devices such as computers and digital home appliances, and further improvement in recording density is required. Therefore, in recent years, a perpendicular magnetic recording system that can realize ultra-high-density recording has attracted attention. Unlike the conventional in-plane recording system, this perpendicular magnetic recording system is said to have a stable recording magnetization as the density increases in principle, and has already been put into practical use. A CoCrPt—SiO ₂ granular magnetic recording film has been proposed as a promising candidate for a material to be applied to the recording layer of this perpendicular magnetic recording type hard disk medium, and this CoCrPt—SiO ₂ granular magnetic recording film is a Co containing Cr and Pt. It is known to produce by a magnetron sputtering method using a sputtering target having a mixed phase of a base sintered alloy phase and a silicon dioxide phase (see Non-Patent Document 1).
This sputtering target usually contains silicon dioxide powder, Cr powder, Pt powder and Co powder, silicon dioxide: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol%, and the balance : It is known that it is prepared by mixing and mixing so as to have a composition composed of Co, and then vacuum hot pressing or hot isostatic pressing, and commercially available Co-based alloy powder containing Cr and Pt. Alternatively, a Co-based alloy powder and silicon dioxide powder containing Cr and Pt prepared by rapid solidification contain silicon dioxide: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol%, and the balance : It is known that it is prepared by mixing and mixing so as to have a composition composed of Co, followed by vacuum hot pressing or hot isostatic pressing. (See Patent Document 1, Patent Document 2, etc.).
Further, in addition to the SiO ₂ , nonmagnetic materials such as TiO, Cr ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , BeO ₂ , MgO, ThO ₂ , ZrO ₂ , CeO ₂ , and Y ₂ O _3. It is known that oxides can be used (see Patent Documents 3 and 4).
“Fuji Times” Vol. 75No. 3 2002 (pages 169-172) Japanese Patent Laid-Open No. 2001-236643 JP 2004-339586 A JP 2003-36525 A JP 2006-24346 A

However, since this sputtering target for forming a magnetic recording medium film is mainly composed of a Co-based alloy containing Cr and Pt, which are ferromagnetic alloys, the magnetic flux passes through the inside of the target compared to a nonmagnetic target. The magnetic flux leaking over the target is extremely small. This is for magnetron sputtering, which has a magnetic circuit placed under the target and stabilizes the discharge by increasing the ionization efficiency of the noble gas by utilizing the magnetic flux leaking over the target, thereby improving the deposition rate. It becomes a big problem. That is, if magnetron sputtering is performed using a target with a low leakage magnetic flux density and a small amount of magnetic flux leaking over the target, the discharge may not be stable or the film formation rate may become extremely slow even if the discharge is possible. .
As one of means for solving this problem, a method is adopted in which the thickness of the target is reduced so that the magnetic flux easily escapes over the target. However, if the target is made thin, the replacement frequency of the target becomes frequent, so that the film formation efficiency is deteriorated, which is not preferable in terms of cost.
In addition, targets with low leakage magnetic flux density are targeted because, once erosion is formed by magnetron sputtering, magnetic flux leaks intensively from the erosion part, and only that part is intensively sputtered. Are likely to cause problems such as a reduction in the use efficiency of the film, a change in the film formation rate over time, a variation in film thickness within the substrate surface, and a large amount of redeposited film deposited on the target.

Therefore, the present inventors conducted research to obtain a sputtering target that can efficiently perform magnetron sputtering without reducing the thickness of the target,
(A) Since the magnetic flux easily passes in a direction with a high relative permeability and does not easily pass in a small direction, the magnetic flux is reduced by reducing the relative permeability in the in-plane direction of the target to 50 or less (more preferably 40 or less). It ’s easier to get over the target,
(B) The inventors have obtained knowledge that the leakage magnetic flux density can be further increased by making the relative permeability in the in-plane direction smaller than the relative permeability in the thickness direction of the target.

This invention has been made based on such knowledge,
(1) Plate-like sintered sputtering containing a non-magnetic oxide: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol%, and the balance: Co and inevitable impurities A sputtering target for forming a perpendicular magnetic recording medium film having an in-plane direction relative permeability of 50 or less and a low in-plane direction relative permeability smaller than a thickness direction relative permeability;
(2) The sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to (1), wherein the in-plane relative relative permeability is 40 or less.

The nonmagnetic oxide contained in the sputtering target for forming a perpendicular magnetic recording medium film having a low in-plane relative permeability according to the present invention is silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide. , Cerium oxide and yttrium oxide. Therefore, the present invention
(3) The (1) or (2), wherein the nonmagnetic oxide is any one of silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide, cerium oxide, and yttrium oxide. And a sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density.

The reason why the in-plane relative permeability of the sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention is limited to 50 or less is that when the in-plane relative permeability exceeds 50, it is disposed below the sputtering target. This is because the magnetic flux generated by the magnet easily passes through the inside of the target, and the ratio of the magnetic flux transmitted to the upper part of the target is reduced. Furthermore, by making the relative permeability in the in-plane direction smaller than the relative permeability in the thickness direction, the magnetic flux due to the magnet becomes difficult to pass through the inside of the target, and a leakage magnetic flux can be more effectively formed on the upper part of the target. .

The sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention is a non-magnetic oxide such as silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide, cerium oxide and yttrium oxide. Material: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol%, the balance: a plate-like sintered body having a composition consisting of Co is maintained at a temperature of 450 ° C. or less. The reduction ratio: 2 to 20%, and can be produced by compressing in the thickness direction.

In the method of manufacturing a sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention, the “reduction ratio” when compressing a plate-like sintered body is the thickness of the original plate-like sintered body. the _{h 1,} when the thickness at the time of completion of all the compressed working process was _{h 2,} is defined by _{(h 1 -h 2) / h} 1 × 100 (%).
The reason why the relative permeability in the in-plane direction is reduced by the compression process is not clear at present, but the following two causes are presumed. First, when the magnetic alloy is compressed, the internal dislocation density increases, and the dislocation hinders the movement of the domain wall and the rotation of the magnetization, so that it is difficult to be magnetized and the relative permeability is lowered. Secondly, the CoCrPt alloy by ordinary powder sintering does not completely transform even when the fcc structure, which is a high-temperature phase, is cooled to room temperature, and tends to be mixed with the hcp structure, which is a low-temperature phase. As a result, part of the remaining fcc phase undergoes strain-induced martensitic transformation and changes to the hcp phase, and the proportion of the hcp phase in the target increases. The hcp phase has a larger magnetic anisotropy than the fcc phase, and when compressed in the thickness direction at a low temperature, the c-axis direction, which is the direction of easy magnetization, tends to be oriented perpendicular to the target surface. As a result, the in-plane direction is occupied by the non-c-axis direction which is not easily magnetized. That is, the fcc phase having a small magnetic anisotropy is decreased, the hcp phase having a large magnetic anisotropy is increased, and the hcp phase exhibits a direction in which it is difficult to be magnetized in the in-plane direction. The thickness becomes smaller and the thickness direction relative permeability becomes larger.

In the manufacturing method of the sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention, the rolling reduction rate of the plate-like sintered body is limited to 2 to 20% because the rolling reduction is less than 2% in the in-plane direction. This is because a target having a sufficiently small relative magnetic permeability cannot be obtained, and it is not preferable. On the other hand, if the rolling reduction exceeds 20%, it is not preferable because cracks occur during compression processing. A more preferable range of the rolling reduction is 4 to 10%. The compression processing performed in the present invention may be any plastic processing method as long as it is a processing method capable of unidirectional compression in the thickness direction of the plate-like sintered body, such as rolling, forging, and pressing.
Further, a plate-like sintered body containing the nonmagnetic oxide: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol%, and the balance: Co and inevitable impurities. The reason why the compression processing is performed at 450 ° C. or lower is that the hcp crystal structure undergoes a phase transition to the fcc crystal structure at temperatures exceeding 450 ° C., and the relative permeability does not decrease even after rolling because the strain is relaxed. This is because it is not preferable. More preferably, it is 400 degrees C or less.

The plate-like sintered body used in the production of the sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention,
Non-magnetic oxide powder: 2 to 15 mol%, Cr powder: 3 to 20 mol%, Pt powder: 5 to 30 mol%, the rest: blended and mixed to form a composition consisting of Co powder, then added Pressure sintering method,
An alloy powder containing any two or more of Co, Cr, and Pt in any composition and a nonmagnetic oxide powder, nonmagnetic oxide: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 A method of containing 30 mol% and the balance: a composition comprising Co and mixing and then pressure sintering, or an alloy powder containing any two or more of Co, Cr and Pt in any composition, Nonmagnetic oxide powder and one or more of Cr powder, Pt powder, and Co powder are nonmagnetic oxide: 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol% A balance: a method of pressure sintering after mixing and mixing so as to be a composition composed of Co,
It can produce by the method of. Specifically, the pressure sintering is a vacuum hot press, a hot isostatic press or the like.
The component composition of the plate-like sintered body used for the production of the sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention is already known as the component composition of the sputtering target for forming a perpendicular magnetic recording medium film. Description of the reason for the limitation is omitted because of the component composition.

  When the sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to the present invention is used, magnetron sputtering can be performed efficiently, which can greatly contribute to the development of industries such as computers and digital home appliances.

As raw material powder, commercially available 50% particle size: 10 μm Co powder, 50% particle size: 15 μm Pt powder, 50% particle size: 10 μm Cr powder, all 50% particle size: 3 μm SiO ₂ powder, TiO ₂ , Ta ₂ O ₅ powder and Al ₂ O ₃ were prepared.

Example 1
These raw material powders are blended so as to have a component composition containing Cr: 10.8%, Pt: 15.3%, SiO ₂ : 10.0% in mol%, with the balance being Co and inevitable impurities. The obtained blended powder was put into a 10-liter container together with zirconia balls as a grinding medium, the atmosphere in the container was replaced with an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled in a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1200 ° C., pressure: 15 MPa, and 3 hours.

The plate-like hot press body was cut into a plate having a thickness of 6.5 mm, and then rolled so as to achieve the rolling reduction shown in Table 1 at the temperature shown in Table 1. In order to apply uniform rolling during rolling, rolling at a constant roll interval is performed in one direction, and then rotated 90, 180, and 270 degrees from the original direction at the same roll interval for a total of 4 times. The rolling was performed, and the four-direction cross rolling was performed, and then the desired rolling reduction was obtained by repeating this while narrowing the roll interval. The present invention targets 1 to 8 and comparative targets 1 to 3 having dimensions of diameter: 152.4 mm and thickness: 5 mm were produced by cutting the rolled sheet thus obtained. Further, a conventional target 1 having a diameter of 152.4 mm and a thickness of 5 mm was manufactured by cutting without rolling.

  The present invention targets 1 to 8, comparative targets 1 to 3, and conventional target 1 are measured for the in-plane maximum relative permeability, the thickness direction maximum relative permeability, and the leakage magnetic flux density leaking over the conventional target 1 by the following method. The results are shown in Table 1.

(I) Measurement of maximum relative permeability in in-plane direction:
A cube sample having a side of 5 mm was cut out from the targets obtained by the present invention targets 1 to 8, the comparative targets 1 to 3, and the conventional target 1. With respect to this cubic sample, a direct current magnetic field of up to 4 × 10 ⁵ A / m is applied in the in-plane direction with a commercially available direct current magnetization measuring apparatus, a magnetization / magnetic field curve (MH curve) is drawn, and the initial magnetization curve is drawn. On the other hand, a tangent line is drawn from the origin, the inclination is obtained, the maximum relative magnetic permeability in the in-plane direction is obtained by the inclination +1, and the result is shown in Table 1.

(B) Measurement of maximum relative permeability in the thickness direction:
A cube sample having a side of 5 mm was cut out from the targets obtained by the present invention targets 1 to 8, the comparative targets 1 to 3, and the conventional target 1. With respect to this cubic sample, a DC magnetic field of up to 4 × 10 ⁵ A / m is applied in the thickness direction with a commercially available DC magnetization measuring device, and a magnetization / magnetic field curve (MH curve) is drawn. Then, a tangent line is drawn from the origin, the inclination is obtained, the maximum relative permeability in the in-plane direction is obtained by the inclination +1, and the result is shown in Table 1.

(C) Measurement of leakage magnetic flux density:
The measurement of the leakage magnetic flux density was performed based on ASTM F2086-01. The measuring jig is made of a non-magnetic material (for example, aluminum). As shown in FIG. 1, the target is a table on which a target is placed, a fixing jig for fixing a magnet placed under the target, and a hole probe. It is comprised from the support | pillar which hold | maintains in the sky and can be moved to the up-down direction or the circular arc direction centering on the support | pillar. A horseshoe-shaped magnet (Dalter Alnico magnet 5K215) was used as a magnet for generating magnetic flux. As a measurement procedure, first, a magnet and a hall probe were attached and fixed to a measurement jig, and a gauss meter was connected to the hall probe. The magnetic flux density horizontal to the target was measured while swinging the hall probe slightly to the left and right in the arc direction without placing the target, and the hall probe was fixed where the magnetic flux density was maximum. The magnetic flux density in the direction horizontal to the table surface measured at this position was defined as a Source Field defined by ASTM, and it was confirmed that it was in the range of 90 ± 5 mT.
Next, raise the tip of the Hall probe to the thickness of the target + 0.5 mm, measure the magnetic flux density in the direction parallel to the table surface while swinging the Hall probe slightly to the left and right in the arc direction, Then, the hole probe was fixed. The magnetic field measured at this position was recorded as a Reference field defined by ASTM.
On the other hand, a sufficiently demagnetized target (demagnetized so that the residual magnetic flux density in the direction perpendicular to the target on the target surface was 0.3 mT or less) was placed on a table. At this time, the position of the hole probe was fixed as described above, and the target was slid from below. The target was arranged so that the distance between the center of the target surface and a point immediately below the hole probe on the target surface was 43.7 ± 2 mm. Next, the target was rotated 5 times counterclockwise so as to be uniformly magnetized. The magnetic flux density in the horizontal direction was recorded on the table surface measured after the rotation, and this was used as the magnetic flux density at the 0 degree position. Furthermore, the magnetic flux density was recorded at positions rotated 30 degrees, 60 degrees, 90 degrees and 120 degrees counterclockwise without moving the target to the center position.
These values were divided by the value of the reference field and multiplied by 100, and an average of 5 points was taken. The 5-point average value was shown in Table 1 as the leakage magnetic flux density (%) of the target.

  From the results shown in Table 1, it can be seen that the present invention targets 1 to 8 have a larger leakage magnetic flux density than the conventional target 1. However, it can be seen that Comparative Targets 1 to 3 having conditions outside the scope of the present invention are not preferable because the characteristics are deteriorated or cracks occur during compression processing.

Example 2
The raw material powder prepared earlier contains, in mol%, Cr: 9.9%, Pt: 13.5%, TiO ₂ : 10.0%, with the balance being a component composition consisting of Co and inevitable impurities. Then, the obtained blended powder was put into a 10-liter container together with zirconia balls as a grinding medium, the atmosphere in the container was replaced with an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled in a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 1000 ° C., pressure: 15 MPa, and 3 hours.

The plate-like hot press body was cut into a plate having a thickness of 6.5 mm, and then rolled so as to achieve the rolling reduction shown in Table 2 at the temperature shown in Table 2. In order to apply uniform rolling during rolling, rolling at a constant roll interval is performed in one direction, and then rotated 90, 180, and 270 degrees from the original direction at the same roll interval for a total of 4 times. The rolling was performed, and the four-direction cross rolling was performed, and then the desired rolling reduction was obtained by repeating this while narrowing the roll interval. By cutting the rolled plate thus obtained, the present invention targets 9 to 16 and comparative targets 4 to 6 having a diameter of 152.4 mm and a thickness of 5 mm were produced. Further, a conventional target 2 having a diameter of 152.4 mm and a thickness of 5 mm was manufactured by cutting without rolling.

  For the present invention targets 9 to 16, comparative targets 4 to 6 and conventional target 2, the in-plane direction maximum relative permeability, the thickness direction maximum relative permeability and the leakage magnetic flux density leaking over the target were measured in the same manner as in Example 1. The results are shown in Table 2.

  From the results shown in Table 2, it can be seen that the present invention targets 9 to 16 have a higher leakage magnetic flux density than the conventional target 2. However, it can be seen that the targets produced with the comparative targets 4 to 6 under conditions outside the scope of the present invention are not preferable because the characteristics are deteriorated or cracks are generated during compression processing.

Example 3
Cr raw material powder prepared in advance in mole%: 13.4%, Pt: 15.4 %, Ta 2 O 5: containing 4.0%, so the balance of the component composition consisting of Co and inevitable impurities The resulting blended powder was put into a 10-liter container together with zirconia balls as a grinding medium, the atmosphere in the container was replaced with an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled into a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under the conditions of temperature: 1050 ° C., pressure: 15 MPa, and holding for 3 hours.

The plate-like hot press body was cut into a plate having a thickness of 6.5 mm, and then rolled so that the rolling reduction shown in Table 3 was achieved at the temperature shown in Table 3. In order to apply uniform rolling during rolling, rolling at a constant roll interval is performed in one direction, and then rotated 90, 180, and 270 degrees from the original direction at the same roll interval for a total of 4 times. The rolling was performed, and the four-direction cross rolling was performed, and then the desired rolling reduction was obtained by repeating this while narrowing the roll interval. The present invention targets 17 to 24 and comparative targets 7 to 9 having dimensions of diameter: 152.4 mm and thickness: 5 mm were produced by cutting the rolled plate thus obtained. Furthermore, the conventional target 3 having a diameter of 152.4 mm and a thickness of 5 mm was manufactured by cutting without rolling.

  For the inventive targets 17 to 24, comparative targets 7 to 9 and conventional target 3, the in-plane direction maximum relative permeability, the thickness direction maximum relative permeability and the leakage magnetic flux density leaking over the target were measured in the same manner as in Example 1. The results are shown in Table 3.

  From the results shown in Table 3, it can be seen that the present invention targets 17 to 24 have a higher leakage magnetic flux density than the conventional target 3. However, it can be seen that the comparative targets 7 to 9 having conditions outside the scope of the present invention are not preferable because the characteristics are deteriorated or cracks are generated during compression processing.

Example 4
Cr raw material powder prepared in advance in mole%: 14.7%, Pt: 14.7 %, Al 2 O 3: containing 8.0%, so the balance of the component composition consisting of Co and inevitable impurities The resulting blended powder was put into a 10-liter container together with zirconia balls as a grinding medium, the atmosphere in the container was replaced with an Ar gas atmosphere, and then the container was sealed. This container was rotated with a ball mill for 16 hours to produce a mixed powder. The obtained mixed powder was filled in a vacuum hot press apparatus, and a plate-like hot press body was produced by vacuum hot pressing in a vacuum atmosphere under conditions of temperature: 980 ° C., pressure: 15 MPa, and 3 hours.

The plate-like hot press body was cut into a plate having a thickness of 6.5 mm, and then rolled at a temperature shown in Table 4 so that the rolling reduction shown in Table 4 was achieved. In order to apply uniform rolling during rolling, rolling at a constant roll interval is performed in one direction, and then rotated 90, 180, and 270 degrees from the original direction at the same roll interval for a total of 4 times. The rolling was performed, and the four-direction cross rolling was performed, and then the desired rolling reduction was obtained by repeating this while narrowing the roll interval. The present invention targets 25 to 32 and comparative targets 10 to 12 having dimensions of diameter: 152.4 mm and thickness: 5 mm were produced by cutting the rolled plate thus obtained. Further, the conventional target 4 having a diameter of 152.4 mm and a thickness of 5 mm was manufactured by cutting without rolling.

  The in-plane direction maximum relative permeability, the thickness direction maximum relative permeability, and the leakage magnetic flux density leaking over the target were measured for the inventive targets 25-32, the comparative targets 10-12, and the conventional target 4 in the same manner as in Example 1. The results are shown in Table 4.

  From the results shown in Table 4, it can be seen that the present invention targets 25 to 32 have a higher leakage magnetic flux density than the target obtained by the conventional target 4. However, it can be seen that Comparative Targets 10 to 12 under conditions outside the scope of the present invention are not preferable because of deterioration in properties or cracking during compression processing.

It is explanatory drawing for demonstrating the measuring method of a leakage magnetic flux density.

Claims (3)

Non-magnetic oxide: a plate-like sintered sputtering target containing 2 to 15 mol%, Cr: 3 to 20 mol%, Pt: 5 to 30 mol%, and the balance: a component composition consisting of Co and inevitable impurities. A sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density, wherein the in-plane direction relative permeability is 50 or less and the in-plane direction relative permeability is smaller than the thickness direction relative permeability. The sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density according to claim 1, wherein the in-plane relative permeability is 40 or less. 3. The nonmagnetic oxide is any one of silicon dioxide, tantalum oxide, titanium oxide, aluminum oxide, magnesium oxide, thorium oxide, zirconium oxide, cerium oxide, and yttrium oxide. A sputtering target for forming a perpendicular magnetic recording medium film having a high leakage magnetic flux density.

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