JP2009099243A - Perpendicular magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium improving electromagnetic conversion characteristics (especially SNR) by further separating and isolating each of magnetic particles of a magnetic recording layer. <P>SOLUTION: The perpendicular magnetic recording medium includes, successively on a substrate, at least a refinement enhancement layer 20 having a granular structure in which a boundary portion containing a first oxide is formed between nonmagnetic particles continuously formed into a columnar shape and configured to refine the magnetic particles of the magnetic recording layer, a first magnetic recording layer 22a having a granular structure in which a boundary portion containing first and second oxides is formed between magnetic particles continuously grown into a columnar shape, and a second magnetic recording layer 22b having a granular structure in which a boundary portion containing a second oxide is formed between magnetic particles continuously grown into a columnar shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD (hard disk drive) or the like.

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, an information recording capacity exceeding 160 GB has been required for a 2.5-inch diameter perpendicular magnetic recording medium used for HDDs and the like. In order to meet such a demand, one square is required. It is required to realize an information recording density exceeding 250 Gbits per inch.

  In order to achieve a high recording density in a magnetic recording medium used for an HDD or the like, a perpendicular magnetic recording medium of a perpendicular magnetic recording system has recently been proposed. The perpendicular magnetic recording system is adjusted so that the easy axis of magnetization of the magnetic recording layer is oriented in a direction perpendicular to the substrate surface. The perpendicular magnetic recording method can suppress the thermal fluctuation phenomenon as compared with the conventional in-plane recording method, and is suitable for increasing the recording density.

As a magnetic recording medium used in the perpendicular magnetic recording system, a CoCrPt—SiO ₂ perpendicular magnetic recording medium (see Non-Patent Document 1) has been proposed because it exhibits high thermal stability and good recording characteristics. This constitutes a granular structure in which nonmagnetic grain boundary portions are formed between magnetic grains continuously grown in a columnar shape in the magnetic recording layer, and it is intended to combine the refinement of the magnetic grains and the improvement of the coercive force Hc. is there. It is known that an oxide is used for a nonmagnetic grain boundary (a nonmagnetic portion between magnetic grains). For example, any one of SiO ₂ , Cr ₂ O ₃ , TiO, TiO ₂ and Ta ₂ O ₅ is used. Has been proposed (Patent Document 1).

Further, there is a case where a non-magnetic granular structure miniaturization promoting layer (sometimes called an onset layer) in which SiO 2 is segregated at the grain boundary of CoCr non-magnetic metal is provided under the magnetic recording layer (patent document). 2). The miniaturization promoting layer is formed on the Ru underlayer, but the Ru underlayer is a continuous crystal that is not isolated. Therefore, when an attempt is made to form a granular layer on the Ru layer, the separation is not necessarily complete in the initial stage, and the bottom of the granular column is disordered in crystal orientation and is connected to spread left and right. It becomes a state. Disturbance of crystal orientation causes a decrease in SNR and coercive force Hc, and connection of crystal grains also causes a decrease in SNR. Therefore, the miniaturization promoting layer promotes the separation and isolation of the granular (magnetic particles) of the magnetic recording layer even if they are connected by forming the base of such granular material with a non-magnetic material. is there.
T. Oikawa et.al., IEEE Trans. Magn, vol.38, 1976-1978 (2002) JP 2006-024346 A JP 2006-268972 A

  Although the magnetic recording medium has a higher recording density as described above, further improvement in the recording density is required in the future. Important factors for achieving high recording density include improved magnetostatic characteristics such as coercivity Hc and reverse domain nucleation magnetic field Hn, and improved electromagnetic conversion characteristics such as overwrite characteristics and SNR (Signal-Noise Ratio). There are various things. In particular, in order to increase the recording density, it is extremely important to separate and isolate the magnetic particles and improve the SNR.

  As described above, in the perpendicular magnetic recording medium, isolation and miniaturization are realized by segregating oxides at grain boundaries in the magnetic recording layer, and various materials have been studied as oxides. In recent years, two or more magnetic recording layers have been provided, and research has been made to achieve both high coercive force Hc, SNR, and overwrite characteristics.

  The refinement and isolation of magnetic particles are affected by the thickness in the horizontal direction (in-plane direction) of the oxide segregated at the grain boundaries. Increasing the amount of oxide improves the SNR at high recording density. On the other hand, when the amount of oxide is excessively increased, the coercive force Hc and the perpendicular magnetic anisotropy deteriorate, and deterioration of thermal stability and increase of noise become problems. That is, it is effective to contain an oxide at the grain boundary, but the amount of the oxide to be contained naturally has an upper limit, and a limit is beginning to appear in refinement and improvement of isolation.

  Accordingly, an object of the present invention is to provide a perpendicular magnetic recording medium capable of improving electromagnetic conversion characteristics (particularly, SNR) by further promoting the separation and isolation of magnetic particles in a magnetic recording layer.

  The inventors have examined oxides that form grain boundaries for the purpose of separating and isolating magnetic particles. Conventionally, in order to improve the crystal orientation of magnetic particles in a magnetic recording layer, a Ru underlayer has been provided, In order to eliminate the influence of the initial stage of growth, a miniaturization promoting layer was provided. These all started from Ru hcp crystals and assumed that the crystal grains of Co particles were continuously epitaxially grown in a columnar shape.

  In contrast, when the crystal grains grow across a plurality of layers including the miniaturization promoting layer, the first magnetic recording layer, and the second magnetic recording layer, the crystal grains are not necessarily in a one-to-one relationship at the interface. We focused on the fact that it does not necessarily grow correspondingly. That is, even if the granular structure is smoothly formed in the lower layer, when moving to the next chamber and forming the upper layer with a new material combination, for example, one on two pillars. If the column stands, the crystal grains are not sufficiently refined.

  The inventors have conceived that if not only crystal grains are continuously grown but also grain boundaries are continuously grown, the crystal grains can be grown in a one-to-one correspondence. On the other hand, for the miniaturization promoting layer, the first magnetic recording layer, and the second magnetic recording layer, it is necessary to select the type of oxide according to the required function. Therefore, the inventors have found that separation and isolation of magnetic particles can be further promoted if the grain boundaries can be continued even if different oxides are used, and the present invention has been completed.

  That is, a typical configuration of the perpendicular magnetic recording medium according to the present invention has a granular structure in which a grain boundary portion including a first oxide is formed at least between nonmagnetic particles continuously grown in a columnar shape on a substrate. And a granular structure in which a grain boundary portion including a first oxide and a second oxide is formed between a magnetic grain that is refined in a magnetic recording layer and a magnetic grain that is continuously grown in a columnar shape. A first magnetic recording layer and a second magnetic recording layer having a granular structure in which a grain boundary portion containing a second oxide is formed between magnetic grains continuously grown in a columnar shape are provided in this order. And

  According to the above configuration, by adding both the miniaturization promoting layer and the oxide contained in the second magnetic recording layer to the first magnetic recording layer, the affinity between the grain boundaries at each interface can be increased. Accordingly, not only crystal grains but also grain boundaries continuously grow, and the separation and isolation of the magnetic grains of the second magnetic recording layer as the main recording layer can be further promoted, and the electromagnetic conversion characteristics (especially SNR) can be improved. Can do.

The first oxide or the second oxide can be selected from SiO ₂ , TiO ₂ , CrO ₂ , Cr ₂ O ₃ , ZrO ₂ , and Ta ₂ O ₅ . The oxide may be any substance that can form a grain boundary around the magnetic grains so that the exchange interaction between the magnetic grains (magnetic grains) is suppressed or blocked.

  In particular, the first oxide may be SiO2, and the second oxide may be TiO2. This is because SiO2 is preferably used in the miniaturization promoting layer in order to promote miniaturization, and TiO2 is preferably used in the second magnetic recording layer because a high SNR can be obtained.

  According to the perpendicular magnetic recording medium of the present invention, it is possible to further increase the recording density by accelerating the separation and isolation of the magnetic particles of the magnetic recording layer and improving the electromagnetic conversion characteristics (especially SNR).

[First Embodiment]
A first embodiment of a method for manufacturing a perpendicular magnetic recording medium according to the present invention will be described. FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium according to the first embodiment. Note that dimensions, materials, and other specific numerical values shown in the following embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified.

  FIG. 1 is a diagram for explaining the configuration of a perpendicular magnetic recording medium 100 according to the first embodiment. The perpendicular magnetic recording medium 100 shown in FIG. 1 includes a disk substrate 10, an adhesion layer 12, a first soft magnetic layer 14a, a spacer layer 14b, a second soft magnetic layer 14c, an orientation control layer 16, a first underlayer 18a, and a second layer. The underlayer 18b, the miniaturization promoting layer 20, the first magnetic recording layer 22a, the second magnetic recording layer 22b, the auxiliary recording layer 24, the medium protective layer 26, and the lubricating layer 28 are formed. The first soft magnetic layer 14a, the spacer layer 14b, and the second soft magnetic layer 14c together constitute the soft magnetic layer 14. The first base layer 18a and the second base layer 18b together constitute the base layer 18. The first magnetic recording layer 22a and the second magnetic recording layer 22b together constitute the magnetic recording layer 22.

  First, an amorphous aluminosilicate glass was formed into a disk shape by direct pressing to produce a glass disk. The glass disk was subjected to grinding, polishing, and chemical strengthening in order to obtain a smooth non-magnetic disk base 10 made of a chemically strengthened glass disk.

  On the disk base 10 obtained, a film forming apparatus that has been evacuated is used to sequentially form a film from the adhesion layer 12 to the auxiliary recording layer 24 in an Ar atmosphere by a DC magnetron sputtering method, thereby protecting the medium protective layer. No. 26 was formed by CVD. Thereafter, the lubricating layer 28 was formed by dip coating. Note that it is also preferable to use an in-line film forming method in terms of high productivity. Hereinafter, the configuration and manufacturing method of each layer will be described.

  The adhesion layer 12 was formed using a Ti alloy target so as to be a 10 nm Ti alloy layer. By forming the adhesion layer 12, the adhesion between the disk base 10 and the soft magnetic layer 14 can be improved, so that the soft magnetic layer 14 can be prevented from peeling off. As a material of the adhesion layer 12, for example, a CrTi alloy can be used.

  The soft magnetic layer 14 includes AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 14b between the first soft magnetic layer 14a and the second soft magnetic layer 14c. It was configured as follows. As a result, the magnetization direction of the soft magnetic layer 14 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and the perpendicular component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 14 is reduced. Can do. Specifically, the composition of the first soft magnetic layer 14a and the second soft magnetic layer 14c was CoFeTaZr, and the composition of the spacer layer 14b was Ru (ruthenium).

  The orientation control layer 16 has an action of protecting the soft magnetic layer 14 and an action of promoting alignment of crystal grains of the underlayer 18. The material of the orientation control layer can be selected from Ni, Cu, Pt, Pd, Zr, Hf, and Nb. Furthermore, it is good also as an alloy which contains these metals as a main component and contains any one or more additional elements of Ti, V, Ta, Cr, Mo, and W. For example, NiW, CuW, or CuCr can be suitably selected.

  The underlayer 18 has an hcp structure, and the crystal of the hcp structure of the magnetic recording layer 22 can be grown as a granular structure. Therefore, the higher the crystal orientation of the underlayer 18 is, the more the orientation of the magnetic recording layer 22 can be improved. The material of the underlayer can be selected from RuCr and RuCo in addition to Ru. Ru has an hcp structure and can satisfactorily orient a magnetic recording layer containing Co as a main component.

  In this embodiment, the underlayer 18 has a two-layer structure made of Ru. When forming the second base layer 18b on the upper layer side, the Ar gas pressure is set higher than when forming the first base layer 18a on the lower layer side. When the gas pressure is increased, the free movement distance of the plasma ions to be sputtered is shortened, so that the film formation rate is reduced and the crystal orientation can be improved. Further, by increasing the pressure, the size of the crystal lattice is reduced. Since the size of the Ru crystal lattice is larger than that of the Co crystal lattice, if the Ru crystal lattice is made smaller, it approaches that of Co, and the crystal orientation of the Co granular layer can be further improved.

The miniaturization promoting layer 20 is a nonmagnetic granular layer. A nonmagnetic granular layer is formed on the hcp crystal structure of the underlayer 18, and the granular layer of the first magnetic recording layer 22 a is grown thereon, so that the magnetic granular layer can be grown from the initial growth stage (rise). Has the effect of separating. The composition of the miniaturization promoting layer 20 contained SiO ₂ as the first oxide, and was nonmagnetic (CoCr) 88 mol%-(SiO ₂ ) 12 mol%.

  The magnetic recording layer 22 is composed of a thin first magnetic recording layer 22a and a thick second magnetic recording layer 22b.

  As will be described below, the perpendicular magnetic recording medium 100 shown in this embodiment includes a plurality of types of oxides (hereinafter referred to as “composite oxides”) in the first magnetic recording layer 22a of the magnetic recording layer 22. As a result, the complex oxide is segregated at the nonmagnetic grain boundaries.

The first magnetic recording layer 22a contains a plurality of types of oxides (hereinafter referred to as “composite oxides”). As a specific example, SiO ₂ and TiO ₂ are each included in an amount of 5 mol% as an example of a composite oxide (first oxide and second oxide), and (CoCrPt) 90 mol%-(SiO ₂ ) 5 mol%-(TiO 2 ₂ ) A 5 mol% hcp crystal structure was formed. The thickness of the first magnetic recording layer 22a was 5 nm. The nonmagnetic substance Cr and the composite oxide segregated around the magnetic substance Co to form grain boundaries, and the magnetic grains (magnetic grains) formed a columnar granular structure. The magnetic grains were epitaxially grown continuously from the granular structure of the miniaturization promoting layer.

The second magnetic recording layer 22b contained 10 mol% of TiO ₂ as an example of the second oxide, and formed an hcp crystal structure of (CoCrPt) 90 mol%-(TiO ₂ ) 10 mol%. The film thickness of the second magnetic recording layer 22b was 10 nm. Also in the second magnetic recording layer 22b, the magnetic grains formed a granular structure.

  That is, if the composition of the miniaturization promoting layer 20 is CoCrX (X is the first oxide) and the composition of the second magnetic recording layer 22b is CoCrPtY (Y is the second oxide), the composition of the first magnetic recording layer 22a is CoCrPt (X + Y) was used.

FIG. 2 shows the composition of the miniaturization promoting layer, the first magnetic recording layer, and the second magnetic recording layer converted from the above mol% notation to the atomic% notation. Referring to FIG. 2, when the composition of the miniaturization promoting layer 20 is CoCrX ₁ , the composition of the second magnetic recording layer 22b is CoCrPtY ₁ , and the composition of the first magnetic recording layer 22a is CoCrPt (X ₂ + Y ₂ ), X _It can be seen that ₁ > X ₂ and Y ₁ > Y ₂ are satisfied.

  The auxiliary recording layer 24 is a thin film (continuous layer) that exhibits high perpendicular magnetic anisotropy and high saturation magnetization MS on the granular magnetic layer. The auxiliary recording layer 24 is intended to improve the reverse domain nucleation magnetic field Hn, the heat-resistant fluctuation characteristics, and the overwrite characteristics. The composition of the auxiliary recording layer 24 was CoCrPtB.

  The medium protective layer 26 was formed by depositing carbon by a CVD method while maintaining a vacuum. The medium protective layer 26 is a protective layer for protecting the perpendicular magnetic recording layer from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness compared to that deposited by the sputtering method, so that the perpendicular magnetic recording layer can be protected more effectively against the impact from the magnetic head.

  The lubricating layer 28 was formed by dip coating using PFPE (perfluoropolyether). The film thickness of the lubricating layer 28 is about 1 nm.

  Through the above manufacturing process, the perpendicular magnetic recording medium 100 was obtained.

(Examples and evaluation)
As described above, the oxide (X1) of the miniaturization promoting layer 20 is SiO ₂ and is 12 mol%.

FIG. 3 is a diagram showing SNR [dB] with respect to the oxide content (mol%). From this figure, if the content of TiO ₂ that is the oxide of the second magnetic recording layer 22b is first examined, the SNR is the highest at 10 mol%, so that the oxide (Y1) of the second magnetic recording layer 22b The amount is preferably in the range of 8 mol% to 12 mol%. In this example, Y1 was 10 mol%.

FIG. 4 is a diagram showing SNR [dB] with respect to the amount and ratio of X2 (the same oxide as the miniaturization promoting layer 20) and Y2 (the same oxide as the second magnetic recording layer 22b) in the first magnetic recording layer 22a. is there. In the figure, Example 1 has a total oxide amount (hereinafter referred to as “total oxide amount”) of 6 mol%, Example 2 has a total oxide amount of 10 mol%, and Example 3 has a total oxide amount of 12 mol%. Comparative Example 1 is CoCrPt—Cr ₂ O ₃ containing Cr ₂ O ₃ as a single oxide.

  Referring to FIG. 4, Examples 1 to 3 each have the highest SNR when the same amounts of oxides X2 and Y2 are contained. Therefore, it can be seen that when the two oxides are combined, a ratio of approximately 1: 1 is preferable.

  Further, referring to Examples 1 to 3, Example 2 having a total oxide amount of 10 mol% has the highest SNR. However, when X2 is 3 mol% or less or 7 mol% or more, the SNR is lower than that of the comparative example. From these facts, the total oxide amount is 10 mol%, and X2 is preferably 3 mol% <X2 <7 mol%, and accordingly Y2 is preferably 7 mol%> Y2> 3 mol%.

  As described above, by adding both the miniaturization promoting layer 20 and the oxide (X, Y) contained in the second magnetic recording layer 22b to the first magnetic recording layer 22a, the affinity between the grain boundaries at each interface is increased. Can increase the sex. Accordingly, not only crystal grains but also grain boundaries continuously grow, and the separation and isolation of the magnetic grains of the second magnetic recording layer as the main recording layer can be further promoted, and the electromagnetic conversion characteristics (especially SNR) can be improved. Can do.

  In addition, by including a plurality of types of oxides (first oxide and second oxide) in the grain boundary portion of the first magnetic recording layer 22a, the characteristics of the plurality of oxides can be obtained together. . Accordingly, it is possible to obtain a perpendicular magnetic recording medium that can improve the electromagnetic conversion characteristics (especially SNR) while improving the magnetostatic characteristics (particularly the coercive force Hc) and can further increase the recording density.

[Second Embodiment]
A second embodiment of the method for manufacturing a perpendicular magnetic recording medium according to the present invention will be described. Note that dimensions, materials, and other specific numerical values shown in the following embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

  FIG. 5 is a diagram for explaining the configuration of the perpendicular magnetic recording medium 102 according to the second embodiment. The perpendicular magnetic recording medium 102 shown in FIG. 5 includes a disk substrate 110, an adhesion layer 112, a first soft magnetic layer 114a, a spacer layer 114b, a second soft magnetic layer 114c, an orientation control layer 116, a first underlayer 118a, and a second layer. The underlayer 118b, the miniaturization promoting layer 120, the first magnetic recording layer 122a, the second magnetic recording layer 122b, the auxiliary recording layer 124, the medium protective layer 126, and the lubricating layer 128 are included. The first soft magnetic layer 114a, the spacer layer 114b, and the second soft magnetic layer 114c together constitute the soft magnetic layer 114. The first base layer 118a and the second base layer 118b together constitute the base layer 118. The first magnetic recording layer 122a and the second magnetic recording layer 122b together constitute the magnetic recording layer 122.

  As will be described below, the perpendicular magnetic recording medium 102 shown in the present embodiment has a plurality of types of oxides (one or both of the first magnetic recording layer 122a and the second magnetic recording layer 122b of the magnetic recording layer 122). Hereinafter, the composite oxide is segregated at the nonmagnetic grain boundaries by containing “composite oxide”.

  As the disk base 110, a glass disk obtained by forming amorphous aluminosilicate glass into a disk shape by direct pressing can be used. The type, size, thickness, etc. of the glass substrate are not particularly limited. Examples of the glass substrate material include glass ceramics such as aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, or crystallized glass. It is done. The glass disk is subjected to grinding, polishing, and chemical strengthening sequentially to obtain a smooth nonmagnetic disk base 10 made of a chemically strengthened glass disk.

  On the disk substrate 110, the adhesion layer 112 to the auxiliary recording layer 124 are sequentially formed by DC magnetron sputtering, and the medium protective layer 126 can be formed by CVD. Thereafter, the lubricating layer 128 can be formed by dip coating. Note that it is also preferable to use an in-line film forming method in terms of high productivity. Hereinafter, the configuration and manufacturing method of each layer will be described.

  The adhesion layer 112 is an amorphous underlayer, which is formed in contact with the disk substrate 110 and has a function of increasing the peel strength between the soft magnetic layer 114 formed on the disk substrate 110 and the disk substrate 110. It has a function of miniaturizing and homogenizing the crystal grain of each layer to be formed. When the disk substrate 110 is made of amorphous glass, the adhesion layer 112 is preferably an amorphous alloy film so as to correspond to the amorphous glass surface.

  The adhesion layer 112 can be selected from, for example, a CrTi amorphous layer, a CoW amorphous layer, a CrW amorphous layer, a CrTa amorphous layer, and a CrNb amorphous layer. Among these, a CrTi alloy film is particularly preferable because it forms an amorphous metal film containing microcrystals. The adhesion layer 112 may be a single layer made of a single material, or may be formed by laminating a plurality of layers. For example, a CoW layer or a CrW layer may be formed on the CrTi layer. These adhesion layers 112 are preferably formed by sputtering with a material containing carbon dioxide, carbon monoxide, nitrogen, or oxygen, or the surface layer is exposed with these gases.

  The soft magnetic layer 114 is a layer that temporarily forms a magnetic path during recording in order to pass magnetic flux in a direction perpendicular to the recording layer in the perpendicular magnetic recording method. The soft magnetic layer 114 is provided with AFC (Antiferro-magnetic exchange coupling) by interposing a nonmagnetic spacer layer 114b between the first soft magnetic layer 114a and the second soft magnetic layer 114c. Can be configured. As a result, the magnetization direction of the soft magnetic layer 114 can be aligned along the magnetic path (magnetic circuit) with high accuracy, and the vertical component of the magnetization direction is extremely reduced, so that noise generated from the soft magnetic layer 114 is reduced. Can do. The composition of the first soft magnetic layer 114a and the second soft magnetic layer 114c includes a cobalt-based alloy such as CoTaZr, a Co—Fe-based alloy such as CoCrFeB and FeCoTaZr, and a Ni like a [Ni—Fe / Sn] n multilayer structure. A Fe alloy or the like can be used.

  The orientation control layer 116 is a nonmagnetic alloy layer, and acts to protect the soft magnetic layer 114 and the easy magnetization axis of the hexagonal close-packed structure (hcp structure) included in the underlayer 118 formed thereon is a disk. A function for aligning in the vertical direction is provided. The orientation control layer 116 preferably has a (111) plane of a face-centered cubic structure (fcc structure) parallel to the main surface of the disk substrate 110. Further, the orientation control layer 116 may have a configuration in which these crystal structures and amorphous are mixed. The material of the orientation control layer can be selected from Ni, Cu, Pt, Pd, Zr, Hf, Nb, and Ta. Furthermore, it is good also as an alloy which contains these metals as a main component and contains any one or more additional elements of Ti, V, Ta, Cr, Mo, and W. For example, NiW, CuW, or CuCr can be suitably selected.

  The underlayer 118 has an hcp structure, and has a function of growing a Co hcp crystal of the magnetic recording layer 22 as a granular structure. Therefore, the higher the crystal orientation of the underlayer 18, that is, the more the (0001) plane of the crystal of the underlayer 118 is parallel to the main surface of the disk substrate 110, the more the orientation of the magnetic recording layer 22 is improved. Can do. Ru is a typical material for the underlayer, but in addition, it can be selected from RuCr and RuCo. Since Ru has an hcp structure and the lattice spacing of crystals is close to Co, a magnetic recording layer containing Co as a main component can be well oriented.

  When the underlayer 118 is made of Ru, a two-layer structure made of Ru can be obtained by changing the gas pressure during sputtering. Specifically, when forming the second base layer 118b on the upper layer side, the Ar gas pressure is set higher than when forming the first base layer 118a on the lower layer side. When the gas pressure is increased, the free movement distance of the plasma ions to be sputtered is shortened, so that the film formation rate is reduced and the crystal orientation can be improved. Further, by increasing the pressure, the size of the crystal lattice is reduced. Since the size of the Ru crystal lattice is larger than that of the Co crystal lattice, if the Ru crystal lattice is made smaller, it approaches that of Co, and the crystal orientation of the Co granular layer can be further improved.

The miniaturization promoting layer 120 is a nonmagnetic granular layer. A nonmagnetic granular layer is formed on the hcp crystal structure of the underlayer 118, and the granular layer of the first magnetic recording layer 122a is grown thereon, so that the magnetic granular layer can be grown from the initial growth stage (rise). Has the effect of separating. The composition of the miniaturization promoting layer 120 can have a granular structure by segregating a nonmagnetic substance between nonmagnetic crystal grains made of a Co-based alloy to form a grain boundary. In particular, CoCr—SiO ₂ and CoCrRu—SiO ₂ can be preferably used, and Rh (rhodium), Pd (palladium), Ag (silver), Os (osmium), Ir (iridium), Au (in addition to Ru) Gold) can also be used. A nonmagnetic substance is a substance that can form a grain boundary around magnetic grains so that exchange interaction between magnetic grains (magnetic grains) is suppressed or blocked, and is cobalt (Co). Any non-magnetic substance that does not dissolve in solution can be used. Examples thereof include silicon oxide (SiOx), chromium (Cr), chromium oxide (CrO ₂ ), titanium oxide (TiO ₂ ), zircon oxide (ZrO ₂ ), and tantalum oxide (Ta ₂ O ₅ ).

The magnetic recording layer 122 has a columnar granular structure in which a nonmagnetic substance is segregated around a magnetic particle of a hard magnetic material selected from a Co-based alloy, an Fe-based alloy, and a Ni-based alloy to form a grain boundary. Yes. By providing the miniaturization promoting layer 20, the magnetic grains can be continuously epitaxially grown from the granular structure. The magnetic recording layer may be a single layer, but in this embodiment, the magnetic recording layer is composed of a first magnetic recording layer 122a and a second magnetic recording layer 122b having different compositions and film thicknesses. The first magnetic recording layer 122a and the second magnetic recording layer 122b are all non-magnetic materials such as oxides such as SiO ₂ , Cr ₂ O ₃ , TiO ₂ , B ₂ O ₃ , Fe ₂ O ₃ , BN, etc. Nitride and carbides such as B ₄ C ₃ can be preferably used.

In this embodiment, two or more nonmagnetic substances are used in combination with the first magnetic recording layer 122a. That is, if the composition of the miniaturization promoting layer 120 is CoCrX (X is the first oxide) and the composition of the second magnetic recording layer 122b is CoCrPtY (Y is the second oxide), the composition of the first magnetic recording layer 122a. Is CoCrPt (X + Y). Further, two or more nonmagnetic substances may be used in combination in the second magnetic recording layer 122b, or CoCrPt (Y + α). Although there is no limitation on the kind of nonmagnetic substance contained at this time, it is particularly preferable to include SiO ₂ and TiO ₂ , and Cr ₂ O ₃ can be suitably used instead of / in addition to either of them. For example, the grain boundary portion of the miniaturization promoting layer 120 contains Cr ₂ O ₃ as an example of an oxide, and the grain boundary portion of the first magnetic recording layer 122a is an example of a complex oxide (plural types of oxides). as to _Cr 2 _{O 3} content and the SiO _2, the second magnetic recording layer 22b can be configured to contain SiO _2.

  The auxiliary recording layer 124 is a layer (also called a continuous layer) that is magnetically continuous in the in-plane direction on the magnetic recording layer 122 having a granular structure. Although the auxiliary recording layer 124 is not necessarily required, by providing the auxiliary recording layer 124, in addition to the high density recording property and low noise property of the magnetic recording layer 122, the reverse magnetic domain nucleation magnetic field Hn is improved, the heat resistance fluctuation characteristic is improved, and the overwrite is performed. The characteristics can be improved.

  The auxiliary recording layer 124 may be not a single layer but a CGC structure (Coupled Granular Continuous) in which a thin film (continuous layer) exhibiting high perpendicular magnetic anisotropy and high saturation magnetization Ms is formed. The CGC structure is an exchange energy control layer comprising a magnetic recording layer having a granular structure, a thin film coupling control layer made of a nonmagnetic material such as Pd or Pt, and an alternating laminated film in which thin films of CoB and Pd are laminated. It can consist of.

  The medium protective layer 126 can be formed by forming a carbon film by a CVD method while maintaining a vacuum. The medium protective layer 126 is a protective layer for protecting the perpendicular magnetic recording layer from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness compared to that deposited by the sputtering method, so that the perpendicular magnetic recording layer can be protected more effectively against the impact from the magnetic head.

  The lubricating layer 128 can be formed of PFPE (perfluoropolyether) by dip coating. PFPE has a long chain molecular structure and binds with high affinity to N atoms on the surface of the medium protective layer 126. Due to the action of the lubricating layer 128, even if the magnetic head comes into contact with the surface of the perpendicular magnetic recording medium 102, damage or loss of the medium protective layer 126 can be prevented.

  Through the above manufacturing process, the perpendicular magnetic recording medium 102 can be obtained. The effectiveness of the present invention will be described below using examples and comparative examples.

(Examples and evaluation)
FIG. 6 is a diagram showing the coercive force Hc, SNR, and overall evaluation when the composition of the nonmagnetic material is changed. In FIG. 6, only oxides are shown for easy understanding, and Si is an abbreviation for SiO ₂ , Ti is TiO ₂ , and Cr is Cr ₂ O ₃ . In the following, X is an oxide included in the miniaturization promoting layer 120 (CoCrX: X is a first oxide), Y is an oxide included in the second magnetic recording layer 122b (CoCrPt (Y + α): Y is a second oxide, α Is a third oxide). Examples are those in which the composition of the first magnetic recording layer 122a is CoCrPt (X + Y), and those that do not follow this rule are comparative examples.

Example 10 contains Cr ₂ O ₃ as X and SiO ₂ as Y. Example 11 SiO ₂ as X, containing a SiO ₂ also contains SiO _2, that is, all three layers as Y. In Example 11, TiO ₂ was included as α of the second magnetic recording layer 122b. Example 12 also contains SiO ₂ in all three layers, but the first magnetic recording layer 122a and the second magnetic recording layer 122b both contain SiO ₂ and TiO ₂ . In this case, Y may be considered to be SiO ₂ or may be considered to be TiO ₂ . Example 13 contains Cr ₂ O ₃ as X and SiO ₂ as Y.

In Comparative Example 10, X is Cr ₂ O ₃ and Y is SiO ₂ , but the first magnetic recording layer 122a is SiO ₂ + TiO ₂ and does not contain X. In Comparative Example 11, X is SiO ₂ and Y is SiO ₂ or TiO ₂ , but the first magnetic recording layer 122a is Cr ₂ O ₃ and does not contain X or Y. In Comparative Example 12, X is SiO ₂ and Y is TiO ₂ , but none of the first magnetic recording layer 122a is included. In Comparative Example 13, X is Ta ₂ O ₅ and Y is TiO ₂ , but none of the first magnetic recording layer 122a is included.

  As can be seen from FIG. 6, in Examples 10 to 13 in which the composition of the first magnetic recording layer 122a is CoCrPt (X + Y), the coercive force Hc and SNR satisfy the required amounts. On the other hand, in Comparative Examples 10 to 13, both Hc and SNR are low, and in particular, SNR does not satisfy the required amount. Therefore, it is not necessary to simply combine a plurality of oxides, and oxides (X, Y) included in the miniaturization promoting layer 120 and the second magnetic recording layer 122b in the first magnetic recording layer 122a. It can be seen that a composite oxide containing both is suitable as a nonmagnetic substance for the magnetic recording layer.

  As described above, by adding both the miniaturization promoting layer 20 and the oxide (X, Y) contained in the second magnetic recording layer 22b to the first magnetic recording layer 22a, the affinity between the grain boundaries at each interface is increased. Can increase the sex. Accordingly, not only the crystal grains but also the grain boundaries continuously grow, and the separation and isolation of the first magnetic recording layer 122a can be further promoted. Accordingly, the magnetic grains of the second magnetic recording layer, which is the main recording layer. Can be further promoted.

  According to the above configuration, both the holding force Hc and the SNR can be improved. By improving the coercive force Hc, the track width can be reduced. Further, the recording bit length can be shortened by improving the SNR. For these reasons, the recording density can be further increased.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used as a perpendicular magnetic recording medium mounted on a perpendicular magnetic recording type HDD or the like.

It is a figure explaining the structure of the perpendicular magnetic recording medium concerning 1st Embodiment. The composition of the miniaturization promoting layer, the first magnetic recording layer, and the second magnetic recording layer is converted from the mol% notation to the atomic% notation. It is a figure which shows SNR with respect to content of an oxide. It is a figure which shows SNR with respect to the quantity and ratio of X2 and Y2 in a 1st magnetic recording layer. It is a figure explaining the structure of the perpendicular magnetic recording medium concerning 2nd Embodiment. It is a figure which shows coercive force Hc, SNR, and comprehensive evaluation when changing a composition of a nonmagnetic substance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Disk base | substrate 12 ... Adhesion layer 14 ... Soft magnetic layer 14a ... 1st soft magnetic layer 14b ... Spacer layer 14c ... 2nd soft magnetic layer 16 ... Orientation control layer 18 ... Underlayer 18a ... 1st underlayer 18b ... 2nd Underlayer 20 ... miniaturization promoting layer 22 ... magnetic recording layer 22a ... first magnetic recording layer 22b ... second magnetic recording layer 24 ... auxiliary recording layer 26 ... medium protective layer 28 ... lubricating layer 100 ... perpendicular magnetic recording medium

Claims (3)

At least on the substrate,
A miniaturization promoting layer having a granular structure in which a grain boundary portion containing a first oxide is formed between nonmagnetic particles continuously grown in a columnar shape and miniaturizing magnetic particles of a magnetic recording layer;
A first magnetic recording layer having a granular structure in which a grain boundary portion including a first oxide and a second oxide is formed between magnetic grains continuously grown in a columnar shape;
A second magnetic recording layer having a granular structure in which a grain boundary portion containing a second oxide is formed between magnetic grains continuously grown in a columnar shape;
Are provided in this order in a perpendicular magnetic recording medium.   The perpendicular magnetic recording medium according to claim 1, wherein the first oxide is SiO 2, and the second oxide is TiO 2. 2. The perpendicular magnetic recording according to claim 1, wherein the first oxide or the second oxide is selected from SiO ₂ , TiO ₂ , CrO ₂ , Cr ₂ O ₃ , ZrO ₂ , and Ta ₂ O _5. Medium.

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