Sputtering targets for magnetic recording media

Abstract

A sputtering target for a magnetic recording medium comprises a metal phase and an oxide phase containing at least B and O, wherein the metal phase comprises at least one selected from Mn and V, Pt, and the remainder of Co and inevitable impurities.

Description

Technical Field

[0001] The present invention relates to a sputtering target for a magnetic recording medium, and more particularly to a sputtering target containing Co, Pt and an oxide. Background Art

[0002] In the disk of a hard disk drive, information signals are recorded in tiny bytes of magnetic recording media. In order to further improve the recording density of magnetic recording media, it is necessary to reduce the size of a byte that holds recorded information while also increasing the signal-to-noise ratio, which is an indicator of information quality. In order to increase the signal-to-noise ratio, it is essential to increase the signal or reduce the noise.

[0003] Currently, magnetic thin films having a granular structure of CoPt-based alloy-oxide are used as magnetic recording media for recording information signals (see, for example, Non-Patent Document 1). The granular structure is composed of columnar CoPt-based alloy grains and grain boundaries of oxide surrounding the grains.

[0004] When increasing the recording density of such a magnetic recording medium, it is necessary to smooth the transition region between recording bits to reduce noise. In order to smooth the transition region between recording bits, it is necessary to refine the CoPt-based alloy grains contained in the magnetic thin film.

[0005] On the other hand, when the magnetic crystal grains are miniaturized, the intensity of the recorded signal that can be maintained by one magnetic crystal grain decreases. In order to achieve both miniaturization of the magnetic crystal grains and the intensity of the recorded signal, the distance between the centers of the crystal grains needs to be reduced.

[0006] On the other hand, when the CoPt-based alloy grains in the magnetic recording medium are refined, the so-called thermal fluctuation phenomenon may occur, that is, the thermal stability of the recorded signal is impaired due to the superparamagnetic phenomenon, causing the recorded signal to disappear. This thermal fluctuation phenomenon is a major obstacle to the high recording density of the magnetic disk.

[0007] In order to solve this obstacle, for each CoPt-based alloy grain, it is necessary to increase the magnetic energy so that the magnetic energy overcomes the thermal energy. The magnetic energy of each CoPt-based alloy grain is determined by the product v×Ku of the volume v of the CoPt-based alloy grain and the magnetocrystalline anisotropy constant Ku. Therefore, in order to increase the magnetic energy of the CoPt-based alloy grain, it is essential to increase the magnetocrystalline anisotropy constant Ku of the CoPt-based alloy grain (for example, see non-patent document 2).

[0008] In addition, in order to make the CoPt-based alloy grains with large Ku grow in a columnar shape, it is necessary to achieve phase separation between the CoPt-based alloy grains and the grain boundary material. When the phase separation between the CoPt-based alloy grains and the grain boundary material is insufficient and the inter-grain interaction between the CoPt-based alloy grains increases, the coercive force Hc of the magnetic film composed of the granular structure of the CoPt-based alloy-oxide decreases, the thermal stability is impaired, and the thermal fluctuation phenomenon is easily generated. Therefore, it is also important to reduce the inter-grain interaction between the CoPt-based alloy grains.

[0009] The refinement of magnetic crystal grains and the reduction of the center-to-center distance of magnetic crystal grains may be achieved by refining the crystal grains of the Ru underlayer (underlayer provided for the purpose of controlling the orientation of the magnetic recording medium).

[0010] However, it is difficult to refine the grains of the Ru underlayer while maintaining the crystal orientation (see, for example, Non-Patent Document 3). Therefore, the grain size of the Ru underlayer of the existing magnetic recording medium is about 7nm to 8nm, which is almost the same as when the in-plane magnetic recording medium is changed to the perpendicular magnetic recording medium.

[0011] On the other hand, from the perspective of improving the magnetic recording layer without targeting the Ru base layer, research has also been conducted to promote the miniaturization of magnetic grains. Specifically, the following method has been studied: the amount of oxide added to the CoPt-based alloy-oxide magnetic film is increased to reduce the volume ratio of the magnetic grains, thereby miniaturizing the magnetic grains (for example, see non-patent document 4). And the miniaturization of magnetic grains is achieved by this method. However, in this method, the width of the grain boundary is increased by increasing the amount of oxide added, so the center-to-center distance of the magnetic grains cannot be reduced.

[0012] In addition, the following method has been studied: in addition to the single oxide used in the existing CoPt-based alloy-oxide magnetic film, a second oxide is added (for example, see non-patent document 5). However, in the case of adding multiple oxide materials, the selection policy of the materials is still unclear, and even now, research on oxides used as grain boundary materials for CoPt-based alloy grains is still continuing. The inventors have found that oxides containing low melting points and high melting points (specifically, B2O3 with a melting point as low as 450°C and high melting point oxides containing a melting point higher than the melting point of the CoPt alloy (about 1450°C)) are effective, and proposed a sputtering target for magnetic recording media containing a CoPt-based alloy and oxide containing B2O3 and a high melting point oxide (Patent Document 1).

[0013] Prior art literature

[0014] Patent Literature

[0015] Patent Document 1: WO2018 / 083951

[0016] Non-patent literature

[0017] Non-patent document 1: T. Oikawa et al., IEEE TRANSACTIONS ON MACNETICS, September 2002, VOL.38, NO.5, p.1976-1978

[0018] Non-patent document 2: SNPiramanayagam, JOURNAL OF APPLIED PH YSICS, 2007, 102, 011301

[0019] Non-patent document 3: SNPiramanayagam et al., APPLIED PHYSICS LETTERS, 2006, 89, 162504

[0020] Non-patent document 4: Y. Inaba et al., IEEE TRANSACTIONS ON MAG NETICS, July 2004, VOL.40, NO.4, p.2486-2488

[0021] Non-patent document 5: I. Tamai et al., IEEE TRANSACTIONS ON MAG NETICS, November 2008, VOL.44, NO.11, p.3492-3495 Summary of the invention

[0022] Problems to be solved by the invention

[0023] An object of the present invention is to provide a sputtering target for a magnetic recording medium capable of producing a magnetic thin film having improved uniaxial magnetic anisotropy, reduced intergranular exchange coupling, and improved thermal stability and SNR (signal-to-noise ratio) in order to further increase capacity.

[0024] Methods used to solve problems

[0025] The inventors discovered that, unlike the control of oxide components adopted in Patent Document 1, by focusing on the metal components and using a sputtering target having an alloy phase containing V or Mn, the decrease in the magnetocrystalline anisotropy constant Ku of the magnetic film obtained by sputtering can be suppressed to a minimum, α can be reduced, and they realized that it is possible to achieve an improvement in uniaxial magnetic anisotropy and a reduction in exchange coupling between grains, thereby completing the present invention.

[0026] According to the present invention, there is provided a sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase containing at least B and O, wherein the metal phase contains at least one selected from Mn and V, Pt, and the remainder Co and inevitable impurities.

[0027] Preferably, the sputtering target for magnetic recording medium contains more than 1 mol % and less than 30 mol % of Pt, more than 0.5 mol % and less than 10 mol % of at least one selected from Mn and V, relative to the total of the metal phase components of the sputtering target for magnetic recording medium, and contains more than 25 volume % and less than 40 volume % of the above-mentioned oxide phase relative to the whole of the sputtering target for magnetic recording medium.

[0028] In addition, according to the present invention, there is provided a sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase containing at least B and O, wherein the metal phase comprises at least one selected from Mn and V, at least one selected from Cr and Ru, Pt, and the remainder Co and inevitable impurities.

[0029] Preferably, the sputtering target for magnetic recording medium contains 1 mol% to 30 mol% of Pt, 0.5 mol% to 10 mol% of at least one selected from Mn and V, and greater than 0.5 mol% to 30 mol% of at least one selected from Cr and Ru, relative to the total of the metal phase components of the sputtering target for magnetic recording medium, and contains 25 volume % to 40 volume % of the above-mentioned oxide phase.

[0030] The above-mentioned oxide phase containing at least B and O may also contain an oxide of at least one element selected from V, Ru, Ti, Si, Ta, Cr, Al, Nb, Mn, Co, Ni, Zn, Y, Mo, W, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr.

[0031] Furthermore, according to the present invention, there is provided a sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase, wherein the metal phase comprises at least one selected from Mn and V, Pt, and the balance of Co and inevitable impurities.

[0032] Preferably, the sputtering target for magnetic recording medium contains more than 1 mol % and less than 30 mol % of Pt, more than 0.5 mol % and less than 10 mol % of at least one selected from Mn and V, relative to the total of the metal phase components of the sputtering target for magnetic recording medium, and contains more than 25 volume % and less than 40 volume % of the above-mentioned oxide phase relative to the whole of the sputtering target for magnetic recording medium.

[0033] According to the present invention, there is provided a sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase, wherein the metal phase comprises at least one selected from Mn and V, at least one selected from Cr and Ru, Pt, and the remainder Co and inevitable impurities.

[0034] Preferably, the sputtering target for magnetic recording medium contains 1 mol% to 30 mol% of Pt, 0.5 mol% to 10 mol% of at least one selected from Mn and V, and greater than 0.5 mol% to 30 mol% of at least one selected from Cr and Ru, relative to the total of the metal phase components of the sputtering target for magnetic recording medium, and contains 25 volume % to 40 volume % of the above-mentioned oxide phase.

[0035] The above-mentioned oxide phase may also contain an oxide of at least one element selected from B, V, Ru, Ti, Si, Ta, Cr, Al, Nb, Mn, Co, Ni, Zn, Y, Mo, W, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr.

[0036] Effects of the Invention

[0037] By using the sputtering target for a magnetic recording medium of the present invention, it is possible to produce a high-recording-density magnetic recording medium having improved thermal stability and SNR by increasing uniaxial magnetic anisotropy and reducing inter-crystalline grain exchange coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 These are photographs of a cross section in the thickness direction of the sintered body test piece in Example 1 observed using a scanning electron microscope (accelerating voltage: 15 keV) (upper stage: 900 times, lower stage: 3000 times).

[0039] Figure 2 yes Figure 1 The lower part (3000 times) is the EDS analysis photo.

[0040] Figure 3 is the granular medium magnetization curve of Example 1.

[0041] Figure 4 These are photographs of a cross section in the thickness direction of the sintered body test piece in Example 2 observed using a scanning electron microscope (accelerating voltage: 15 keV) (upper stage: 900 times, lower stage: 3000 times).

[0042] Figure 5 yes Figure 4 The lower part (3000 times) is the EDS analysis photo.

[0043] Figure 61 and 2 are XRD distribution diagrams of the magnetic films of Examples 1 and 2 and Comparative Example 1 in a direction perpendicular to the film surface.

[0044] Figure 7 These are TEM observation images of the magnetic films of Examples 1 and 2 and Comparative Example 1 (film formation thickness: 16 nm).

[0045] Figure 8 It is a graph showing the measurement results of Ms of the magnetic films of Examples 1 and 2 and Comparative Example 1.

[0046] Fig. 9 It is a graph showing the measurement results of Hc of the magnetic films of Examples 1 and 2 and Comparative Example 1.

[0047] Fig.10 It is a graph showing the measurement results of Hn of the magnetic films of Examples 1 and 2 and Comparative Example 1.

[0048] Fig.11 This is a graph showing α of the magnetic films of Examples 1 and 2 and Comparative Example 1.

[0049] Fig.12 is the Ku of the magnetic films of Examples 1, 2 and Comparative Example 1 Grain A graph of the measurement results. DETAILED DESCRIPTION

[0050] Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. It should be noted that in this specification, a sputtering target for a magnetic recording medium may be simply referred to as a sputtering target or a target.

[0051] (1) First Embodiment

[0052] The sputtering target for a magnetic recording medium according to the first embodiment of the present invention is characterized by comprising a metal phase and an oxide phase containing at least B and O, wherein the metal phase contains at least one selected from Mn and V, Pt, and the remainder Co and inevitable impurities.

[0053] The target of the first embodiment preferably contains more than 1 mol % and less than 30 mol % of Pt, more than 0.5 mol % and less than 10 mol % of at least one selected from Mn and V, the balance of the metal phase is Co and unavoidable impurities, and contains more than 25 volume % and less than 40 volume % of an oxide phase containing at least B and O relative to the whole sputtering target for magnetic recording media.

[0054] The oxide phase containing B and O refers to a phase containing boron oxide. As boron oxide, B2O3 is generally used, but it also includes oxides in which B and O are combined in a non-stoichiometric ratio. However, since it is difficult to analyze the non-stoichiometric boron oxide itself, it is assumed that all B identified in the ICP analysis of the boron oxide is B2O3 for calculation. In this specification, boron oxide is also set as B2O3 for explanation.

[0055] One or more selected from Mn and V, Co and Pt become constituent components of magnetic grains (tiny magnets) in the granular structure of the magnetic thin film formed by sputtering. Hereinafter, in this specification, one or more selected from Mn and V will be abbreviated as "X", and the magnetic grains contained in the magnetic thin film of the magnetic recording medium formed using the target of the first embodiment will also be referred to as "CoPtX alloy grains".

[0056] Co is a ferromagnetic metal element and plays a core role in the formation of magnetic grains (tiny magnets) in the granular structure of the magnetic film. From the viewpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPtX alloy grains (magnetic grains) in the magnetic film obtained by sputtering and maintaining the magnetism of the CoPtX alloy grains (magnetic grains) in the obtained magnetic film, it is preferred to set the content ratio of Co in the sputtering target of the first embodiment to 25 mol% or more and 98.5 mol% or less relative to the total metal component.

[0057] Pt has the function of reducing the magnetic moment of the alloy by alloying with Co and X within a predetermined composition range, and has the effect of adjusting the magnetic strength of the magnetic grains. From the viewpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPtX alloy grains (magnetic grains) in the magnetic film obtained by sputtering and adjusting the magnetic properties of the CoPtX alloy grains (magnetic grains) in the magnetic film obtained, it is preferred that the content ratio of Pt in the sputtering target of the first embodiment is set to 1 mol% or more and 30 mol% or less relative to the total metal component.

[0058] The inventors have found that V and Mn have the function of improving the separation of CoPtX alloy grains (magnetic grains) caused by the oxide phase in the magnetic film, and can reduce the exchange coupling between grains. When comparing a magnetic film formed by sputtering using a CoPtX-B2O3 target (X = V or Mn) with a magnetic film formed by sputtering using a CoPt-B2O3 target, the B2O3 oxide phase that is the wall of adjacent CoPtX alloy grains exists deeper in the depth direction ( Figure 7 : TEM observation image), the slope α of the position where the magnetization curve intersects the horizontal axis (load magnetic field) is smaller ( Fig.11), it can be confirmed that the separability of magnetic crystal grains is improved. On the other hand, the magnetocrystalline anisotropy constant Ku per unit particle grain For the same Fig.12 ), it can be confirmed that the uniaxial magnetic anisotropy of the magnetic film is good. From the examples described below, it is found that V reduces α more and reduces Ku less than Mn, so it can be said that V is more preferable.

[0059] The content ratio of X in the sputtering target of the first embodiment is preferably set to 0.5 mol% or more and 10 mol% or less relative to the entire metal phase component, more preferably 1 mol% or more and less than 10 mol%, and particularly preferably set to 5 mol% or less. Mn and V can be contained as metal phase components of the sputtering target separately or in combination. In particular, by using Mn and V in combination, it is possible to further reduce intergranular exchange coupling and maintain uniaxial magnetic anisotropy, so it is preferred.

[0060] The oxide phase becomes a non-magnetic matrix that separates magnetic grains (micro magnets) from each other in the granular structure of the magnetic thin film. The oxide phase of the sputtering target of the first embodiment contains at least B and O. As other oxides, an oxide of at least one element selected from V, Ru, Ti, Si, Ta, Cr, Al, Nb, Mn, Co, Ni, Zn, Y, Mo, W, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr may be contained. As other oxides, specifically, VO2, VO3, V2O5, RuO2, TiO2, SiO2, Ta2O5, Cr2O3, Al2O3, Nb2O5, MnO, Mn3O4, CoO, Co3O4, NiO, ZnO, Y2O3, MoO2, WO3, La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Yb2O3, Lu2O3 and ZrO2 can be listed.

[0061] The melting point of B2O3, which is a general boron oxide, is as low as 450°C, so it precipitates later in the film formation process using sputtering, and exists in a liquid state between the columnar CoPtX alloy grains during the period when the CoPtX alloy grains grow in a columnar shape. Therefore, B2O3 eventually precipitates in the form of grain boundaries that separate the CoPtX alloy grains that grow in a columnar shape, and becomes a non-magnetic matrix that separates the magnetic grains (tiny magnets) from each other in the granular structure of the magnetic film. Increasing the content of oxide in the magnetic film makes it easier to reliably separate the magnetic grains from each other and to make the magnetic grains independent of each other, so it is preferred. From this point of view, the content of oxide contained in the sputtering target of the first embodiment is preferably 25% by volume or more, more preferably 28% by volume or more, and further preferably 29% by volume or more. However, when the content of oxide in the magnetic film is too much, the oxide is mixed into the CoPtX alloy grains (magnetic grains), which has an adverse effect on the crystallinity of the CoPtX alloy grains (magnetic grains), and the proportion of structures other than hcp in the CoPtX alloy grains (magnetic grains) may increase. In addition, the number of magnetic grains per unit area in the magnetic film is reduced, so it is difficult to increase the recording density. From these aspects, the content of the oxide phase contained in the sputtering target of the first embodiment is preferably 40% by volume or less, more preferably 35% by volume or less, and further preferably 31% by volume or less.

[0062] In the sputtering target of the first embodiment, the total content ratio of the metal phase components relative to the entire sputtering target and the total content ratio of the oxide phase components relative to the entire sputtering target are determined by the component composition of the target magnetic film and are not particularly limited. However, the total content ratio of the metal phase components relative to the entire sputtering target can be set, for example, to be greater than 89.4 mol% and less than 96.4 mol%, and the total content ratio of the oxide phase components relative to the entire sputtering target can be set, for example, to be greater than 3.6 mol% and less than 11.6 mol%.

[0063] The microstructure of the sputtering target of the first embodiment is not particularly limited, but is preferably a microstructure in which a metal phase and an oxide phase are finely dispersed with each other. By forming such a microstructure, defects such as nodules and particles are less likely to occur during sputtering.

[0064] The sputtering target according to the first embodiment can be produced, for example, as follows.

[0065] The metal components are weighed to obtain a predetermined composition to prepare a CoPt alloy melt. Then, gas atomization is performed to prepare a CoPt alloy atomized powder. The prepared CoPt alloy atomized powder is classified to a predetermined particle size or less (for example, 106 μm or less).

[0066] To the prepared CoPt alloy atomized powder are added one or more X metal powders selected from V and Mn, B2O3 powder and other oxide powders as needed (for example, TiO2 powder, SiO2 powder, Ta2O5 powder, Cr2O3 powder, Al2O3 powder, ZrO2 powder, Nb2O5 powder, MnO powder, Mn3O4 powder, CoO powder, Co3O4 powder, NiO powder, ZnO powder, Y2O3 powder, MoO2 powder, WO3 powder, La2O3 powder, CeO2 powder, Nd2O3 powder, Sm2O3 powder, Eu2O3 powder, Gd2O3 powder, Yb2O3 powder and Lu2O3 powder) and mixed and dispersed using a ball mill to prepare a mixed powder for pressure sintering. By mixing and dispersing CoPt alloy atomized powder, X metal powder, B2O3 powder and other oxide powders as needed using a ball mill, a mixed powder for pressure sintering can be produced in which CoPt alloy atomized powder, X metal powder, B2O3 powder and other oxide powders as needed are finely dispersed with each other.

[0067] For the magnetic thin film made using the obtained sputtering target, from the viewpoint of using B2O3 and other oxides as needed to reliably separate the magnetic grains from each other and thus easily make the magnetic grains independent of each other, from the viewpoint of making it easy for the CoPtX alloy grains (magnetic grains) to form an hcp structure, and from the viewpoint of improving the recording density, the total volume percentage of B2O3 powder and other oxide powders as needed relative to the total mixed powder for pressure sintering is preferably 25 volume % or more and 40 volume %, more preferably 28 volume % or more and 35 volume %, and further preferably 29 volume % or more and 31 volume %.

[0068] For example, the mixed powder for pressure sintering produced by vacuum hot pressing is pressure sintered and formed to produce a sputtering target. The mixed powder for pressure sintering is mixed and dispersed using a ball mill, and CoPt alloy atomized powder, X metal powder, B2O3 powder and other oxide powders as required are finely dispersed with each other, so when the sputtering target obtained by this manufacturing method is used for sputtering, it is not easy to produce defects such as nodules and particles. It should be noted that the method for pressure sintering the mixed powder for pressure sintering is not particularly limited, and can be a method other than vacuum hot pressing, such as HIP method, etc.

[0069] When preparing the mixed powder for pressure sintering, it is not limited to atomized powder, and powders of each metal element may also be used. In this case, each metal element powder, B2O3 powder and other oxide powders as required may be mixed and dispersed using a ball mill to prepare the mixed powder for pressure sintering.

[0070] Furthermore, other oxides may be oxides formed by oxidizing at least a part of Co, V, and Mn, which are raw materials of the metal phase, when the mixed powder for pressure sintering is produced or sintered.

[0071] (2) Second Embodiment

[0072] The sputtering target for magnetic recording media according to the second embodiment of the present invention is characterized in that it comprises a metal phase and an oxide phase containing at least B and O, wherein the metal phase comprises at least one selected from Mn and V, at least one selected from Cr and Ru, Pt, the remainder Co and inevitable impurities.

[0073] The target of the second embodiment preferably contains a metal phase comprising 1 mol % or more and 30 mol % or less of Pt, greater than 0.5 mol % and less than 30 mol % of at least one selected from Cr and Ru, greater than 0.5 mol % and less than 10 mol % of at least one selected from Mn and V, the remainder being Co and unavoidable impurities, and contains 25 volume % or more and 40 volume % or less of an oxide containing at least B and O relative to the whole sputtering target for magnetic recording media.

[0074] The oxide phase containing B and O refers to a phase containing boron oxide. As boron oxide, B2O3 is generally used, but it also includes oxides in which B and O are combined in a non-stoichiometric ratio. However, since it is difficult to analyze the non-stoichiometric boron oxide itself, it is assumed that all B identified in the ICP analysis of the boron oxide is B2O3 for calculation. In this specification, boron oxide is also set as B2O3 for explanation.

[0075] One or more selected from Mn and V (hereinafter also referred to as "X"), one or more selected from Cr and Ru (hereinafter also referred to as "M"), Co and Pt are constituent components of magnetic grains (tiny magnets) in the granular structure of the magnetic thin film formed by sputtering. Hereinafter, in this specification, the magnetic grains of the second embodiment are also referred to as "CoPtXM alloy grains".

[0076] Co is a ferromagnetic metal element and plays a core role in the formation of magnetic grains (tiny magnets) in the granular structure of the magnetic film. From the viewpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPtXM alloy grains (magnetic grains) in the magnetic film obtained by sputtering and maintaining the magnetism of the CoPtXM alloy grains (magnetic grains) in the obtained magnetic film, it is preferred to set the content ratio of Co in the sputtering target of the second embodiment to 25 mol% or more and 98 mol% or less relative to the total metal component.

[0077] Pt has the function of reducing the magnetic moment of the alloy by alloying with Co, X and M within a predetermined composition range, and has the effect of adjusting the magnetic strength of the magnetic grains. From the viewpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPtXM alloy grains (magnetic grains) in the magnetic film obtained by sputtering and adjusting the magnetic properties of the CoPtXM alloy grains (magnetic grains) in the magnetic film obtained, it is preferred that the content ratio of Pt in the sputtering target of the second embodiment is set to 1 mol% or more and 30 mol% or less relative to the total metal phase component.

[0078] At least one selected from Cr and Ru has the function of reducing the magnetic moment of Co by alloying with Co within a prescribed composition range, and has the effect of adjusting the magnetic strength of magnetic grains. From the viewpoint of increasing the magnetocrystalline anisotropy constant Ku of the CoPtXM alloy grains (magnetic grains) in the magnetic film obtained by sputtering and maintaining the magnetism of the CoPtXM alloy grains in the obtained magnetic film, it is preferred to set the content ratio of at least one selected from Cr and Ru in the sputtering target of the second embodiment to be greater than 0.5 mol% and less than 30 mol% relative to the overall metal phase components. Cr and Ru can be used alone or in combination to form the metal phase of the sputtering target together with Co and Pt. As will be seen from the examples described later, Ru is more capable of reducing the reduction in Ku than Cr, so it can be said that Ru is more preferred.

[0079] The inventors have found that V and Mn have the function of improving the separability of CoPtXM alloy grains (magnetic grains) caused by the oxide phase in the magnetic film, and can reduce the exchange coupling between grains. On the other hand, the magnetocrystalline anisotropy constant Ku will not be greatly reduced. It is clear from the examples described below that V can reduce α more and Ku less than Mn, so it can be said that V is more preferable.

[0080] The content ratio of X in the sputtering target of the second embodiment is preferably set to 0.5 mol% or more and 10 mol% or less relative to the entire metal phase component, more preferably 1 mol% or more and less than 10 mol%, and particularly preferably set to 5 mol% or less. Mn and V can be contained as metal phase components of the sputtering target separately or in combination. In particular, by using V and Mn in combination, it is possible to reduce intergranular exchange coupling and improve uniaxial magnetic anisotropy, so it is preferred.

[0081] The oxide phase becomes a non-magnetic matrix that separates magnetic grains (micro magnets) from each other in the granular structure of the magnetic thin film. The oxide phase of the sputtering target of the second embodiment contains at least B and O. As other oxide components, an oxide of at least one element selected from V, Ru, Ti, Si, Ta, Cr, Al, Nb, Mn, Co, Ni, Zn, Y, Mo, W, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr may be contained. As other oxides, specifically, VO2, VO3, V2O5, RuO2, TiO2, SiO2, Ta2O5, Cr2O3, Al2O3, Nb2O5, MnO, Mn3O4, CoO, Co3O4, NiO, ZnO, Y2O3, MoO2, WO3, La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Yb2O3, Lu2O3 and ZrO2 can be listed.

[0082] The melting point of B2O3, which is a general boron oxide, is as low as 450°C. Therefore, in the film forming process using sputtering, the precipitation period is relatively late, and during the period when the CoPtXM alloy grains grow in a columnar shape, it exists in a liquid state between the columnar CoPtXM alloy grains. Therefore, B2O3 finally precipitates in the form of a grain boundary that separates the CoPtXM alloy grains that grow in a columnar shape, and becomes a non-magnetic matrix that separates the magnetic grains (tiny magnets) from each other in the granular structure of the magnetic film. Increasing the content of oxide in the magnetic film makes it easier to reliably separate the magnetic grains from each other and to make the magnetic grains independent of each other, so it is preferred. From this point of view, the content of oxide contained in the sputtering target of the second embodiment is preferably 25% by volume or more, more preferably 28% by volume or more, and further preferably 29% by volume or more. However, when the content of oxide in the magnetic film is too much, the oxide is mixed into the CoPtXM alloy grains (magnetic grains), which has an adverse effect on the crystallinity of the CoPtXM alloy grains (magnetic grains), and the proportion of structures other than hcp in the CoPtXM alloy grains (magnetic grains) may increase. In addition, the number of magnetic grains per unit area in the magnetic film is reduced, so it is difficult to increase the recording density. From these aspects, the content of the oxide phase contained in the sputtering target of the second embodiment is preferably 40 volume % or less, more preferably 35 volume % or less, and further preferably 31 volume % or less.

[0083] In the sputtering target of the second embodiment, the total content ratio of the metal phase components relative to the entire sputtering target and the total content ratio of the oxide phase components relative to the entire sputtering target are determined by the component composition of the target magnetic film and are not particularly limited. The total content ratio of the metal phase components relative to the entire sputtering target can be set to, for example, greater than 88.2 mol % and less than 96.4 mol %, and the total content ratio of the oxide phase components relative to the entire sputtering target can be set to, for example, greater than 3.6 mol % and less than 11.8 mol %.

[0084] The microstructure of the sputtering target of the second embodiment is not particularly limited, but is preferably a microstructure in which a metal phase and an oxide phase are finely dispersed with each other. By forming such a microstructure, defects such as nodules and particles are less likely to occur during sputtering.

[0085] The sputtering target of the second embodiment can be produced, for example, as follows.

[0086] The M metal powder of one or more selected from Cr and Ru, Co and Pt are weighed in a manner to obtain a predetermined composition to prepare a CoPtM alloy melt. Then, gas atomization is performed to prepare a CoPtM alloy atomized powder. The prepared CoPtM alloy atomized powder is classified to a predetermined particle size or less (e.g., less than 106 μm).

[0087] To the prepared CoPtM alloy atomized powder are added one or more X metal powders selected from V and Mn, B2O3 powder and other oxide powders as needed (for example, TiO2 powder, SiO2 powder, Ta2O5 powder, Cr2O3 powder, Al2O3 powder, ZrO2 powder, Nb2O5 powder, MnO powder, Mn3O4 powder, CoO powder, Co3O4 powder, NiO powder, ZnO powder, Y2O3 powder, MoO2 powder, WO3 powder, La2O3 powder, CeO2 powder, Nd2O3 powder, Sm2O3 powder, Eu2O3 powder, Gd2O3 powder, Yb2O3 powder and Lu2O3 powder), and mixed and dispersed using a ball mill to prepare a mixed powder for pressure sintering. CoPtM alloy atomized powder, X metal powder, B2O3 powder and other oxide powders as needed are mixed and dispersed using a ball mill, thereby producing a mixed powder for pressure sintering in which CoPtM alloy atomized powder, X metal powder, B2O3 powder and other oxide powders as needed are finely dispersed with each other.

[0088] For the magnetic thin film made using the obtained sputtering target, from the viewpoint of utilizing B2O3 and other oxides as needed to reliably separate the magnetic grains from each other and thus easily making the magnetic grains independent of each other, from the viewpoint of easily forming an hcp structure of the CoPtXM alloy grains (magnetic grains), and from the viewpoint of improving the recording density, the total volume percentage of B2O3 powder and other oxide powders as needed relative to the total mixed powder for pressure sintering is preferably 25 volume % or more and 40 volume % or less, more preferably 28 volume % or more and 35 volume % or less, and further preferably 29 volume % or more and 31 volume % or less.

[0089] For example, the pressure sintering mixed powder produced is subjected to pressure sintering and formed by vacuum hot pressing to produce a sputtering target. The pressure sintering mixed powder is mixed and dispersed using a ball mill, and CoPtM alloy atomized powder, X metal powder, B2O3 powder and other oxide powders as required are finely dispersed with each other, so when the sputtering target obtained by this manufacturing method is used for sputtering, it is not easy to produce defects such as nodules and particles. It should be noted that the method for pressure sintering the pressure sintering mixed powder is not particularly limited, and can be a method other than vacuum hot pressing, such as HIP method, etc.

[0090] When preparing the mixed powder for pressure sintering, it is not limited to atomized powder, and powders of each metal element may also be used. In this case, each metal element powder, B powder as required, B2O3 powder and other oxide powders as required may be mixed and dispersed using a ball mill to prepare the mixed powder for pressure sintering.

[0091] Furthermore, other oxides may be oxides formed by oxidizing at least a part of Co, Cr, Ru, V and Mn, which are raw materials of the metal phase, when the mixed powder for pressure sintering is prepared or when sintering.

[0092] (3) Third Embodiment

[0093] A sputtering target for a magnetic recording medium according to a third embodiment of the present invention is characterized by including a metal phase and an oxide phase, wherein the metal phase includes at least one selected from Mn and V, Pt, and the balance Co and inevitable impurities.

[0094] The target of the third embodiment preferably contains a metal phase comprising more than 1 mol % and less than 30 mol % of Pt, more than 0.5 mol % and less than 10 mol % of at least one selected from Mn and V, the remainder Co and inevitable impurities, and contains more than 25 volume % and less than 40 volume % of oxide relative to the whole sputtering target for magnetic recording media.

[0095] The third embodiment is the same as the first embodiment except that the oxide phase is not limited to contain boron oxide, and therefore the description thereof is omitted, and the reason why the oxide phase is not limited to contain boron oxide is described below.

[0096] As shown in the examples described later, if the metal phase contains V or Mn, even if boron oxide is not included as an oxide, the decrease in Ku is small and α is reduced. In the case of containing SiO2 and TiO2 as oxides, not only α is reduced, but Ku is also increased, so it is particularly preferred. In the case of using SiO2, TiO2, Cr2O3, Nb2O5, Ta2O5, MoO3, WO3, CoO, B2O3 and any combination thereof as oxides, it can be confirmed that α is reduced and the decrease in Ku is small. The oxide precipitates in a manner that becomes a grain boundary that separates the CoPtX alloy grains that grow in a columnar shape, and becomes a non-magnetic matrix that separates the magnetic grains (tiny magnets) from each other in the granular structure of the magnetic film.

[0097] The sputtering target for magnetic recording media of the third embodiment may contain, in addition to the above-mentioned oxides, an oxide of at least one element selected from V, Ru, Al, Mn, Co, Ni, Zn, Y, Mo, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr. Specifically, other oxides include VO2, VO3, V2O5, RuO2, Al2O3, MnO, Mn3O4, Co3O4, NiO, ZnO, Y2O3, MoO2, La2O3, CeO2, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Yb2O3, Lu2O3 and ZrO2.

[0098] (4) Fourth Embodiment

[0099] The sputtering target for a magnetic recording medium according to the fourth embodiment of the present invention is characterized by comprising a metal phase and an oxide phase, wherein the metal phase comprises at least one selected from Mn and V, at least one selected from Cr and Ru, Pt, and the remainder of Co and inevitable impurities.

[0100] The target of the fourth embodiment preferably contains a metal phase comprising 1 mol % or more and 30 mol % or less of Pt, greater than 0.5 mol % and less than 30 mol % of at least one selected from Cr and Ru, greater than 0.5 mol % and less than 10 mol % of at least one selected from Mn and V, the remainder Co and unavoidable impurities, and contains 25 volume % or more and 40 volume % of oxides relative to the whole sputtering target for magnetic recording media.

[0101] The fourth embodiment is the same as the second embodiment except that it is not limited to the oxide phase containing boron oxide. Also, the fourth embodiment is the same as the third embodiment in that it can contain any oxide, and thus the description thereof is omitted.

[0102] Example

[0103] Hereinafter, the present invention will be further described using Examples and Comparative Examples.

[0104] (Example 1)

[0105] The overall composition of the target prepared in Example 1 is (75Co-20Pt-5V)-30 volume % B2O3 (the metal component is expressed in atomic ratio), and the molar ratio is 92.47(75Co-20Pt-5V)-7.53B2O3.

[0106] When preparing the target of Example 1, first, a 50Co-50Pt alloy and a 100Co atomized powder were prepared. Specifically, each metal was weighed so that the composition of the alloy atomized powder was Co: 50 atomic % and Pt: 50 atomic %, and both compositions were heated to above 1500° C. to prepare alloy melts, which were gas atomized to prepare 50Co-50Pt alloy and 100Co atomized powders, respectively.

[0107] The prepared 50Co-50Pt alloy and 100Co atomized powder were classified using a 150-mesh sieve to obtain 50Co-50Pt alloy and 100Co atomized powder having a particle size of less than 106 μm, respectively.

[0108] V powder and B2O3 powder are added to the classified 50Co-50Pt alloy and 100Co atomized powder in a manner to obtain a composition of (75Co-20Pt-5V)-30 volume % B2O3, and the mixture is mixed and dispersed using a ball mill to obtain a mixed powder for pressure sintering.

[0109] The obtained mixed powder for pressure sintering was used at a sintering temperature of 810°C, a sintering pressure of 24.5 MPa, a sintering time of 30 minutes, and an atmosphere of 5×10 -2 The sintered body specimen (φ30 mm) was produced by hot pressing under vacuum conditions of less than 1.3 Pa. The relative density of the produced sintered body specimen was 98.8%. It should be noted that the calculated density was 8.90 g / cm 3 The cross section of the obtained sintered body specimen in the thickness direction was mirror-polished and observed using a scanning electron microscope (SEM: JCM-6000Plus manufactured by JEOL) at an accelerating voltage of 15 keV. The obtained results are shown in Figure 1In addition, the composition analysis of the cross-sectional structure was performed using an energy dispersive X-ray spectrometer (EDS) installed in the same device, and the obtained results are shown in Figure 2 From these results, it can be confirmed that the metal phase (75Co-20Pt-5V alloy phase) and the oxide phase (B2O3) are finely dispersed. The obtained sintered body specimens were subjected to ICP analysis, and the obtained results are shown in Table 3.

[0110] Next, the prepared mixed powder for pressure sintering was used at a sintering temperature of 810°C, a sintering pressure of 24.5 MPa, a sintering time of 60 minutes, and an atmosphere of 5×10 -2 The target was hot pressed under vacuum conditions of less than 1.5 psi to produce a target with a size of φ153.0×1.0 mm+φ161.0×4.0 mm. The relative density of the produced target was 98.3%.

[0111] Using the prepared target, a DC sputtering device (ES-3100W manufactured by Electron Grinding) was used to sputter a magnetic thin film composed of (75Co-20Pt-5V)-30 volume % B2O3 on a glass substrate to prepare samples for magnetic property measurement and tissue observation. Specifically, as a layer for ensuring the adhesion between the glass substrate and the metal film, Ta was formed into a 5nm film under the conditions of an Ar gas pressure of 0.6Pa and an input power of 500W. Next, Ni was used as a seed layer for forming an oriented film. 90 W 10 A film of 6 nm was formed at 0.6Pa and 500W. Next, as a hcp structure substrate, Ru was formed into a film of 10 nm at 0.6Pa and 500W, and then, in order to form a surface concave-convex shape, Ru was formed into a film of 10 nm at 8.0Pa and 500W. Furthermore, in order to make the separation of the magnetic columns good, Co-25Cr-50Ru-30 volume% TiO2 was formed into a film of 1 nm at 0.6Pa and 300W. Thereon, as a magnetic layer, (Co-20Pt-5V)-30 volume% B2O3 was formed into films of 4nm, 8nm, 12nm, and 16nm at 4.0Pa and 500W, respectively. Finally, as a surface protective layer, C was formed into a film of 7nm at 0.6Pa and 300W. The layer structures of these samples are represented as Ta(5nm, 0.6Pa) / Ni in order from the side close to the glass substrate. 90 W 10(6nm, 0.6Pa) / Ru(10nm, 0.6Pa) / Ru(10nm, 8.0Pa) / Co-25Cr-50Ru-30vol%TiO2(1nm, 4.0Pa) / (Co-20Pt-5V)-30vol%B2O3(Ynm(Y=4, 8, 12 or 16), 4Pa) / C(7nm, 0.6Pa). The numbers on the left side of the brackets indicate the film thickness, and the numbers on the right side indicate the pressure of the Ar atmosphere during sputtering. The magnetic thin film obtained by film formation using the target prepared in Example 1 is a CoPtV alloy-oxide (B2O3), which is a magnetic thin film that becomes the recording layer of a perpendicular magnetic recording medium. It should be noted that when forming the magnetic thin film, the substrate is not heated, and the film is formed at room temperature.

[0112] In the measurement of the magnetic properties of the obtained samples for measuring magnetic properties, a vibrating sample magnetometer (VSM: TM-VSM211483-HGC manufactured by Tamagawa Manufacturing Co., Ltd.), a torque magnetometer (TM-TR2050-HGC manufactured by Tamagawa Manufacturing Co., Ltd.) and a polar Kerr effect measuring device (MOKE: BH-810CPM-CPC manufactured by Neoac Co., Ltd.) were used.

[0113] An example of the granular medium magnetization curve (Y=12 nm) of the sample for measuring magnetic properties in Example 1 is shown in FIG. Figure 3 . Figure 3 The horizontal axis is the strength of the applied magnetic field, Figure 3 The vertical axis is the intensity of magnetization per unit volume.

[0114] Based on the measurement results of the granular medium magnetization curve of the sample for magnetic property measurement, the saturation magnetization (Ms), coercive force (Hc), reverse magnetic domain nucleation field (Hn), and the slope (α) of the position intersecting the horizontal axis were obtained. In addition, the magnetocrystalline anisotropy constant (Ku) was measured using a torque magnetometer. These values ​​are shown in Table 1 together with the results of other examples and comparative examples. Figure 8 to Figure 12 .

[0115] In addition, in the evaluation of the structure of the obtained sample for tissue observation (evaluation of the particle size of magnetic crystal grains, etc.), an X-ray diffraction device (XRD: SmartLab manufactured by Rigaku Corporation) and a transmission electron microscope (TEM: H-9500 manufactured by Hitachi High-Technologies Corporation) were used. The XRD distribution diagram in the direction perpendicular to the film surface is shown in FIG. Figure 6 and Table 2, the TEM images are shown in Figure 7 .

[0116] (Example 2)

[0117] The composition of the target prepared as Example 2 is (75Co-20Pt-5Mn)-30 volume % B2O3 (metal components are expressed in atomic ratio), and the molar ratio is 92.51(75Co-20Pt-5Mn)-7.49B2O3. Except for changing the composition of the target from Example 1, the samples for magnetic property measurement and tissue observation were prepared and observed in the same manner as Example 1. The results are shown in Figure 4 and Figure 5 The average particle size of the Mn powder used was less than 3 μm, and the sintering temperature was 840°C, the sintering pressure was 24.5 MPa, the sintering time was 30 minutes, and the atmosphere was 5×10 -2 The sintered body specimen (φ30 mm) was produced by hot pressing under vacuum conditions of less than 1.3 Pa. The relative density of the produced sintered body specimen was 102.6%. It should be noted that the calculated density was 8.97 g / cm 3 The thickness cross section of the obtained sintered body specimen was observed using a metal microscope, and it was confirmed that the metal phase (75Co-20Pt-5Mn alloy phase) and the oxide phase (B2O3) were finely dispersed. The results of ICP analysis of the obtained sintered body specimen are shown in Table 3.

[0118] Next, the prepared mixed powder for pressure sintering was used to perform sintering at a sintering temperature of 840°C, a sintering pressure of 24.5 MPa, a sintering time of 60 minutes, and an atmosphere of 5×10 -2 The target was hot pressed under vacuum conditions of less than 100 psi to produce a target of φ153.0×1.0 mm+φ161.0×4.0 mm. The relative density of the produced target was 104.8%.

[0119] Next, the magnetic properties of the film were evaluated and the structure was observed in the same manner as in Example 1. The results of the magnetic property measurements are shown in Table 1 together with the target composition. Figure 8 to Figure 12 In addition, the XRD distribution diagram in the vertical direction of the film surface of the organization observation is shown in Figure 6 and Table 2, the TEM images are shown in Figure 7 .

[0120] (Comparative Example 1)

[0121] The target composition was set to (80Co-20Pt)-30 volume % B2O3 (metal components expressed in atomic ratio), and a sintered body specimen and a target were prepared in the same manner as in Examples 1 and 2, and a magnetic thin film was formed and evaluated. The results of the magnetic properties are shown in Table 1 together with the target composition. Figure 8 to Figure 12 The XRD distribution diagram of the film surface perpendicular to the structure observation is shown in Figure 6 The peak position (2θ) of CoPt (002) and the lattice constant of the C axis read from the XRD distribution diagram are shown in Table 2, and the TEM image is shown in Figure 7 Table 3 shows the results of ICP analysis of the obtained sintered body specimens.

[0122] The meanings of the abbreviations in Table 1 are as follows.

[0123] t Mag1 : Film thickness of the magnetic recording layer in the laminated film

[0124] M s Grain : The saturation magnetization of only the magnetic particles in the magnetic layer of the laminated film

[0125] H c : Coercivity measured using the Kerr effect

[0126] H n :Nucleation field measured using the Kerr effect

[0127] α: The slope of the magnetization curve measured using the Kerr effect at the position where it intersects the horizontal axis (load magnetic field)

[0128] H c -H n : The difference between the coercivity and the nucleation field measured using the Kerr effect

[0129] K u Grain : The magnetocrystalline anisotropy constant of only the magnetic grains in the magnetic layer of the laminated film

[0130] [Table 1]

[0131] Table 1 Magnetic properties measurement results

[0132]

[0133] [Table 2]

[0134] Table 2 CoPt (002) peak position and C-axis lattice constant

[0135]

[0136] [Table 3]

[0137] Table 3 ICP analysis results of sintered specimens

[0138]

[0139] Depend on Figure 6 It can be confirmed from Table 2 that the CoPt (002) peaks of Example 1 (V) and Example 2 (Mn) are shifted to a lower angle compared to Comparative Example 1 (Co). Therefore, it can be said that at least a portion of V or Mn is substituted with Co. However, the change in the lattice constant of the C axis of the CoPt phase calculated from the peak position is In addition, no structural change of the CoPt phase was confirmed. On the other hand, no peak shift was confirmed for Ru and NiW.

[0140] according to Figure 7 It was confirmed that the gaps between adjacent magnetic columns in the magnetic thin film containing V or Mn extended deeper in the depth direction than in the magnetic thin film not containing V or Mn (X=Co). This confirmed that the use of a target containing V or Mn improves the separability of magnetic crystal grains.

[0141] according to Figure 8 It can be seen that compared with Comparative Example 1 (Co), a slight increase in Ms was confirmed in Example 1 (V) and Example 2 (Mn) when the film was formed to 4 nm, but it was roughly the same when the film was formed to 8 nm or more, and the magnetism of the CoPtX alloy grains (magnetic grains) could be maintained.

[0142] according to Fig. 9 , the magnetic film containing V or Mn shows the same or slightly lower Hc than the magnetic film not containing V or Mn (X = Co). However, it is expected to be further improved by optimizing the composition, adding V and Mn in combination, etc.

[0143] according to Fig.10 , a decrease in Hn was observed in Example 1 (V) compared to Comparative Example 1 (Co). A further decrease in Hn was observed in Example 2 (Mn) compared to Example 1 (V). This suggests that the separability of magnetic crystal grains is improved.

[0144] Depend on Fig.11 It was confirmed that the magnetic thin film containing V or Mn showed lower α than the magnetic thin film not containing V or Mn (X=Co), and the separability of magnetic crystal grains was improved.

[0145] Depend on Fig.12 It was confirmed that the magnetic thin film containing V or Mn showed equivalent Ku to the magnetic thin film not containing V or Mn (X=Co), and maintained high uniaxial magnetic anisotropy.

[0146] (Examples 3 to 4, Comparative Example 2)

[0147] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume SiO2, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 4.

[0148] Compared with Comparative Example 2, Examples 3 to 4 containing V or Mn in the metal phase and SiO2 as the oxide phase have lower α and higher Ku. It can be said that the separability of magnetic grains is improved, showing high uniaxial magnetic anisotropy.

[0149] (Examples 5 to 6, Comparative Example 3)

[0150] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume TiO2, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 4.

[0151] Compared with Comparative Example 3, Examples 5 to 6 containing V or Mn in the metal phase and TiO2 as the oxide phase have lower α and higher Ku, which can be said to improve the separability of magnetic grains and show high uniaxial magnetic anisotropy.

[0152] (Examples 7 to 8, Comparative Example 4)

[0153] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume of Cr2O3, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 4.

[0154] Compared with Comparative Example 4, Examples 7 to 8 containing V or Mn in the metal phase and Cr2O3 as the oxide phase have a lower α and a smaller reduction in Ku to less than 0.95. It can be said that the separability of the magnetic grains is improved and a high uniaxial magnetic anisotropy is maintained.

[0155] (Examples 9-10, Comparative Example 5)

[0156] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume of Nb2O5, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 4.

[0157] Compared with Comparative Example 5, Examples 9 to 10 containing V or Mn in the metal phase and Nb2O5 as the oxide phase have a lower α and a smaller reduction in Ku to below 0.39. It can be said that the separability of the magnetic grains is improved and a high uniaxial magnetic anisotropy is maintained.

[0158] (Examples 11 to 12, Comparative Example 6)

[0159] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume Ta2O5, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 4.

[0160] Compared with Comparative Example 6, Examples 11 to 12 containing V or Mn in the metal phase and Ta2O5 as the oxide phase have a lower α and a smaller reduction in Ku to less than 0.47. It can be said that the separability of the magnetic grains is improved and a high uniaxial magnetic anisotropy is maintained.

[0161] (Examples 13-14, Comparative Example 7)

[0162] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume of MoO3, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 5.

[0163] Compared with Comparative Example 7, Examples 13 to 14 containing V or Mn in the metal phase and MoO3 as the oxide phase have lower α and a smaller reduction in Ku to less than 0.30. It can be said that the separability of magnetic grains is improved and high uniaxial magnetic anisotropy is maintained.

[0164] (Examples 15-16, Comparative Example 8)

[0165] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 30% by volume WO3, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 5.

[0166] Compared with Comparative Example 8, Examples 15 to 16 containing V or Mn in the metal phase and WO3 as the oxide phase have lower α and a smaller reduction in Ku to less than 0.51. It can be said that the separability of magnetic grains is improved and high uniaxial magnetic anisotropy is maintained.

[0167] (Examples 17 to 18, Comparative Example 9)

[0168] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 15 volume % B2O3-15 volume % SiO2, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 5.

[0169] Compared with Comparative Example 9, Examples 17 to 18, which contain V or Mn in the metal phase and B2O3 and SiO2 as oxide phases, have a lower α and a smaller reduction in Ku to less than 0.18. It can be said that the separability of the magnetic grains is improved and a high uniaxial magnetic anisotropy is maintained.

[0170] (Examples 19 to 20, Comparative Example 10)

[0171] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 15 volume % SiO2-15 volume % TiO2, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 5.

[0172] Compared with Comparative Example 10, Examples 19 to 20, which contain V or Mn in the metal phase and SiO2 and TiO2 as oxide phases, have a lower α and an increased or very small decrease of 0.01 in Ku. It can be said that the separability of the magnetic grains is improved, showing a high uniaxial magnetic anisotropy.

[0173] (Examples 21-22, Comparative Example 11)

[0174] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 20 volume % B2O3-5 volume % Cr2O3, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 5.

[0175] Compared with Comparative Example 11, Examples 21 to 22, which contain V or Mn in the metal phase and B2O3 and Cr2O3 as oxide phases, have a lower α and a smaller reduction in Ku to below 0.54. It can be said that the separability of the magnetic grains is improved and a high uniaxial magnetic anisotropy is maintained.

[0176] (Examples 23-24, Comparative Example 12)

[0177] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 10 volume % SiO2-10 volume % TiO2-10 volume % CoO, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 5.

[0178] Compared with Comparative Example 12, Examples 23 to 24, which contain V or Mn in the metal phase and SiO2, TiO2 and CoO as oxide phases, have a lower α and a smaller reduction in Ku of 0.35. It can be said that the separability of the magnetic grains is improved, showing a high uniaxial magnetic anisotropy.

[0179] (Examples 25-26, Comparative Example 13)

[0180] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 20 volume % SiO2-5 volume % TiO2-5 volume % CoO, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0181] Compared with Comparative Example 13, Examples 25 to 26, which contain V or Mn in the metal phase and SiO2, TiO2 and CoO as oxide phases, have a lower α and a smaller reduction in Ku of 1.02. It can be said that the separability of the magnetic grains is improved, showing a high uniaxial magnetic anisotropy.

[0182] (Examples 27 to 28, Comparative Example 14)

[0183] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 20 volume % B2O3-5 volume % SiO2-5 volume % Cr2O3, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0184] Compared with Comparative Example 14, Examples 27 to 28, which contain V or Mn in the metal phase and SiO2, TiO2 and CoO as oxide phases, have a lower α and an increased Ku or show a very small decrease of 0.19. It can be said that the separability of the magnetic grains is improved, showing a high uniaxial magnetic anisotropy.

[0185] (Examples 29 to 30, Comparative Example 15)

[0186] Using a sputtering target for magnetic recording media prepared in the same manner as in Examples 1 to 2 and Comparative Example 1 except that the oxide phase was changed to 20 volume % B2O3-3 volume % SiO2-3 volume % TiO2-10 volume % CoO, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0187] Compared with Comparative Example 15, Examples 29 to 30, which contain V or Mn in the metal phase and B2O3, SiO2, TiO2 and CoO as oxide phases, have lower α and higher Ku. It can be said that the separability of magnetic grains is improved, showing high uniaxial magnetic anisotropy.

[0188] (Example 31)

[0189] A magnetic recording medium sputtering target prepared in the same manner as in Example 1 except that the metal phase composition was changed to 79Co-20Pt-1V was used to form a magnetic layer having a thickness of 8 nm in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0190] In Example 31 containing 1 mol % of V in the metal phase, the decrease in α was smaller than that in Example 1 containing 5 mol % of V, but the decrease in Ku was as small as 0.04.

[0191] (Example 32)

[0192] Using a sputtering target for magnetic recording media prepared in the same manner as in Example 2 except that the metal phase composition was changed to 79Co-20Pt-1Mn, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0193] In Example 32 containing 1 mol % of Mn in the metal phase, the decrease in α is smaller than that in Example 2 containing 5 mol % of Mn, but the decrease in Ku is smaller.

[0194] (Example 33)

[0195] A magnetic recording medium sputtering target prepared in the same manner as in Example 1 except that the metal phase composition was changed to 70Co-20Pt-10V was used to form a magnetic layer having a thickness of 8 nm in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0196] In Example 33 in which 10 mol % of V is contained in the metal phase, α is reduced similarly to Example 1 in which 5 mol % of V is contained, but the reduction range of Ku is larger.

[0197] (Example 34)

[0198] Using a sputtering target for magnetic recording media prepared in the same manner as in Example 2 except that the metal phase composition was changed to 70Co-20Pt-10Mn, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0199] In Example 34 in which the metal phase contains 10 mol % of Mn, α is reduced similarly to Example 2 in which the metal phase contains 5 mol % of Mn, but the reduction range of Ku is larger.

[0200] (Comparative Example 16)

[0201] A magnetic recording medium sputtering target prepared in the same manner as in Example 1 except that the metal phase composition was changed to 65Co-20Pt-15V was used to form a magnetic layer having a thickness of 8 nm in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0202] Comparative Example 16 containing 15 mol % of V showed a significantly greater decrease in Ku than Examples 1, 31, and 33 containing 1 to 10 mol % of V.

[0203] (Comparative Example 17)

[0204] Using a sputtering target for magnetic recording media prepared in the same manner as in Example 2 except that the metal phase composition was changed to 65Co-20Pt-15Mn, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0205] Comparative Example 17 containing 15 mol % of Mn has a significantly greater reduction in Ku than Examples 2, 32, and 34 containing 1 to 10 mol % of Mn.

[0206] (Examples 35-36, Comparative Example 18)

[0207] In Example 35, a sputtering target for magnetic recording medium was prepared in the same manner as in Example 1 except that the metal phase composition was changed to 75Co-20Pt-2Cr-3V. In Example 36, a sputtering target for magnetic recording medium was prepared in the same manner as in Example 2 except that the metal phase composition was changed to 75Co-20Pt-2Cr-3Mn. In Comparative Example 18, a sputtering target for magnetic recording medium was prepared in the same manner as in Comparative Example 1 except that the metal phase composition was changed to 75Co-20Pt-5Cr. Using the sputtering targets for magnetic recording medium prepared respectively, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), slope (α) of the position intersecting the horizontal axis, and magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0208] In Examples 35 to 36, which further include Cr in the metal phase composition, the decrease in Ku is smaller than in Examples 1 to 2, and it can be said that the separability of magnetic crystal grains is improved, and high uniaxial magnetic anisotropy is exhibited.

[0209] (Examples 37 to 38, Comparative Example 19)

[0210] In Example 37, a sputtering target for magnetic recording medium was prepared in the same manner as in Example 1 except that the metal phase composition was changed to 75Co-20Pt-2Ru-3V. In Example 38, a sputtering target for magnetic recording medium was prepared in the same manner as in Example 2 except that the metal phase composition was changed to 75Co-20Pt-2Ru-3Mn. In Comparative Example 19, a sputtering target for magnetic recording medium was prepared in the same manner as in Comparative Example 1 except that the metal phase composition was changed to 75Co-20Pt-5Ru. Using the sputtering targets for magnetic recording medium prepared respectively, a magnetic layer having a thickness of 8 nm was formed in the same manner as in Example 1, and the coercive force (Hc), nucleation field (Hn), the slope of the position intersecting the horizontal axis (α), and the magnetocrystalline anisotropy constant (Ku) were measured. The results are shown in Table 6.

[0211] In Examples 37 to 38, which further include Ru in the metal phase composition, the decrease in Ku is smaller than in Examples 1 to 2, and it can be said that the separability of magnetic crystal grains is improved, and high uniaxial magnetic anisotropy is exhibited.

[0212] From the results shown in Tables 4 to 6, it can be seen that when V is included in the metal phase, the decrease in α is greater and the decrease in Ku is smaller than when Mn is included. By including V or Mn, it is possible to achieve an improvement in the separability of magnetic grains and maintain a high uniaxial magnetic anisotropy, and V is effective for further improving the separability of magnetic grains and further maintaining a high uniaxial magnetic anisotropy. In addition, regardless of which oxide is used, it is possible to achieve an improvement in the separability of magnetic grains and maintain a high uniaxial magnetic anisotropy, and it can be said that when SiO2 or TiO2 is included, it has a better effect. In addition, it was confirmed that by including B2O3, the uniaxial magnetic anisotropy (Ku) can be improved, and by including SiO2 or TiO2, a high uniaxial magnetic anisotropy (Ku) can be maintained and α can be reduced.

[0213]

[0214]

[0215]

Claims

1. A sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase containing at least B and O, wherein the metal phase contains at least one selected from Mn and V, Pt, and the remainder of Co and unavoidable impurities, The magnetic recording medium sputtering target contains 1 mol % to 30 mol % of Pt and 0.5 mol % to 10 mol % of at least one selected from Mn and V, based on the total of the metal phase components of the sputtering target. The oxide phase is contained in an amount of 25 volume % or more and 40 volume % or less based on the entirety of the sputtering target for a magnetic recording medium.

2. A sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase containing at least B and O, wherein the metal phase comprises at least one selected from Mn and V, at least one selected from Cr and Ru, Pt, the remainder of Co and unavoidable impurities, and the metal phase does not contain a Co-Ru alloy phase containing 30 mol % or more of Ru, The magnetic recording medium sputtering target contains 1 mol % to 30 mol % of Pt, 0.5 mol % to 10 mol % of at least one selected from Mn and V, and greater than 0.5 mol % to 30 mol % of at least one selected from Cr and Ru, relative to the total of the metal phase components of the sputtering target for the magnetic recording medium. The oxide phase is contained in an amount of 25 volume % or more and 40 volume % or less based on the entirety of the sputtering target for a magnetic recording medium.

3. The sputtering target for a magnetic recording medium according to claim 1 or 2, wherein: The oxide phase also contains an oxide of at least one element selected from V, Ru, Ti, Si, Ta, Cr, Al, Nb, Mn, Co, Ni, Zn, Y, Mo, W, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr.

4. A sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase, wherein the metal phase comprises at least one selected from Mn and V, Pt, the remainder Co and unavoidable impurities The magnetic recording medium sputtering target contains 1 mol % to 30 mol % of Pt and 0.5 mol % to 10 mol % of at least one selected from Mn and V, based on the total of the metal phase components of the sputtering target. The oxide phase is contained in an amount of 25 volume % or more and 40 volume % or less based on the entirety of the sputtering target for a magnetic recording medium.

5. A sputtering target for a magnetic recording medium, comprising a metal phase and an oxide phase, wherein the metal phase comprises at least one selected from Mn and V, at least one selected from Cr and Ru, Pt, the remainder of Co and unavoidable impurities, and the metal phase does not contain a Co-Ru alloy phase containing 30 mol % or more of Ru, The magnetic recording medium sputtering target contains 1 mol % to 30 mol % of Pt, 0.5 mol % to 10 mol % of at least one selected from Mn and V, and greater than 0.5 mol % to 30 mol % of at least one selected from Cr and Ru, relative to the total of the metal phase components of the sputtering target for the magnetic recording medium. The oxide phase is contained in an amount of 25 volume % or more and 40 volume % or less based on the entirety of the sputtering target for a magnetic recording medium.

6. The sputtering target for a magnetic recording medium according to claim 4 or 5, wherein: The oxide phase contains an oxide of at least one element selected from B, V, Ru, Ti, Si, Ta, Cr, Al, Nb, Mn, Co, Ni, Zn, Y, Mo, W, La, Ce, Nd, Sm, Eu, Gd, Yb, Lu and Zr.

7. The sputtering target for a magnetic recording medium according to claim 4 or 5, wherein: The oxide phase contains SiO2, TiO2, Cr2O3, Nb2O5, Ta2O5, MoO3, WO3, CoO, B2O3 or any combination thereof.

Images