JP2014049171A - Magnetic recording medium, and magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which enables higher recording density by maintaining high perpendicular orientation of a perpendicular magnetic layer.SOLUTION: In the magnetic recording medium obtained by laminating, on a nonmagnetic substrate, at least a soft magnetic under layer 30, seed layers 31, 32, an orientation control layer 33, and a perpendicular magnetic layer in this order, the soft magnetic under layer 30 has an amorphous or fine crystal structure, the seed layers 31, 32 include a first seed layer 31 containing one kind, or two kinds or more of ones selected from a group consisting of CeO, YO, CrO, TaC, and ZrC, and a second seed layer 32 formed on the first seed layer in the shape of an island or a net and made of metal, and the orientation control layer 33 and the perpendicular magnetic layer constitute columnar crystals in each of which respective crystal grains continue in a thickness direction with the second seed layer 32 as an original point.

Description

  The present invention relates to a magnetic recording medium and a magnetic recording / reproducing apparatus.

  The recording density of a hard disk drive (HDD), which is a kind of magnetic recording / reproducing device, is currently increasing at an annual rate of 50% or more, and it is said that this trend will continue in the future. Accordingly, development of a magnetic head and a magnetic recording medium suitable for increasing the recording density has been advanced.

  Currently, a magnetic recording medium mounted on a commercially available magnetic recording / reproducing apparatus is a so-called perpendicular magnetic recording medium in which an easy axis of magnetization in a magnetic film is oriented mainly vertically. Even when the recording density of the perpendicular magnetic recording medium is increased, the influence of the demagnetizing field in the boundary region between the recording bits is small and a clear bit boundary is formed, so that an increase in noise can be suppressed. In addition, since the recording bit volume decreases with the increase in recording density, the thermal fluctuation effect is strong. For this reason, in recent years, much attention has been paid and a medium structure suitable for perpendicular magnetic recording has been proposed.

  In order to meet the demand for higher recording density of magnetic recording media, it has been studied to use a single-pole head having excellent writing ability for the perpendicular magnetic layer. In order to cope with such a single magnetic pole head, a layer made of a soft magnetic material called a backing layer is provided between the perpendicular magnetic layer as a recording layer and the nonmagnetic substrate, so that There has been proposed a magnetic recording medium in which the efficiency of magnetic flux in and out of the recording medium is improved.

  However, the magnetic recording / reproducing apparatus using the magnetic recording medium simply provided with the above-mentioned backing layer is not satisfactory in recording / reproducing characteristics, thermal fluctuation resistance, and recording resolution at the time of recording / reproducing, and is excellent in these characteristics. There is a need for magnetic recording media.

  In particular, as recording / reproduction characteristics, it is important to increase the signal / noise ratio (S / N ratio) during reproduction and to increase the S / N ratio and to improve thermal fluctuation resistance. It is an indispensable item in the conversion. However, since these two items have a contradictory relationship, if one of them is improved, one becomes insufficient, and coexistence at a high level is an important issue.

  In order to solve such problems, by combining the three magnetic layers with an AFC (anti-ferro coupling) using a non-magnetic layer, etc., while enjoying the advantage of lowering the synthetic Mrt and PW50 A magnetic recording medium that does not cause a decrease in the S / N ratio has been proposed (see, for example, Patent Document 1).

  Specifically, this Patent Document 1 discloses a substrate, a first lower ferromagnetic layer provided on the substrate, having a remanent magnetization Mr, a thickness t, and a remanent magnetization / thickness product Mrt, and the first A ferromagnetic coupling layer provided on the lower ferromagnetic layer; a second lower ferromagnetic layer having an Mrt value provided on the ferromagnetic coupling layer; and an anti-reflection provided on the second lower ferromagnetic layer. A ferromagnetic coupling layer; and an upper ferromagnetic layer provided on the antiferromagnetic coupling layer and having an Mrt value larger than a total Mrt value of the first and second lower ferromagnetic layers. A magnetic recording medium is described.

  On the other hand, in order to improve the recording / reproducing characteristics and thermal fluctuation characteristics of the perpendicular magnetic recording medium, an orientation control layer is used to form a multi-layered magnetic layer, and the crystal grains of each magnetic layer are formed into continuous columnar crystals. Has been proposed to improve the vertical orientation of the magnetic layer (see, for example, Patent Document 2).

  For example, Ru is disclosed as the orientation control layer. Since Ru has a dome-shaped convex part on the top of the columnar crystal, crystal grains such as a magnetic layer are grown on the convex part, promote the separation structure of the grown crystal grains, and isolate the crystal grains. And has the effect of growing magnetic particles in a columnar shape (see, for example, Patent Document 3).

  In order to refine the columnar crystals constituting the orientation control layer, it has been proposed to provide a NiW alloy layer as a seed layer between the soft magnetic layer and the orientation control layer (see, for example, Patent Document 4). reference.).

  In the magnetic recording medium having a structure having a soft magnetic layer, an intermediate layer, a perpendicular recording layer, and a protective layer on the substrate, the first intermediate layer is formed of Pd, Pt, Au, Ag, Rh, Ru, A metal layer mainly composed of at least one element selected from the group consisting of Ti, the second intermediate layer is an oxygen-containing layer, and the third intermediate layer is Pd, Pt, Au, Ag, Rh , Ru, Ti are metal layers mainly composed of at least one element selected from the group consisting of Ru, Ti, and the fourth intermediate layer is mainly composed of at least one element selected from Co, Cr, Ru, Ti. There has been proposed a magnetic recording medium that is a metal layer as a component, and in which the perpendicular recording layer contains Co as a main component and contains oxygen (see, for example, Patent Document 5).

  In paragraphs [0010] to [0011] of Patent Document 5, the vertical alignment is controlled by the first intermediate layer, and the second intermediate layer containing oxygen and the third intermediate layer are isolated like islands. The recording layer contains oxygen by using a four-layer structure intermediate layer in which a fourth intermediate layer having a hexagonal close-packed structure is formed using the convex structure as a nucleus. It is described that the coercive force and the squareness ratio are improved, the medium noise is reduced, and the heat resistance and demagnetization characteristics are improved.

JP 2005-276410 A JP 2004-310910 A JP 2007-272990 A JP 2007-179598 A JP 2004-134041 A

  By the way, the demand for higher recording density for magnetic recording media is not limited, and magnetic recording media are required to have higher characteristics than ever before. Specifically, in order to increase the recording density of the magnetic recording medium, it is necessary to refine the crystal constituting the orientation control layer described above and to refine the magnetic particles having a columnar structure formed thereon.

  In the invention described in Patent Document 5, the soft magnetic layer and the first intermediate layer are accompanied by heat treatment at a high temperature (see paragraph [0022]). It turned out that enlargement progresses and the refinement | miniaturization of a magnetic particle is inhibited.

  The present invention has been proposed in view of such a conventional situation, and maintains a high perpendicular alignment property of the perpendicular magnetic layer and further increases the recording density, and such a magnetic recording medium. An object of the present invention is to provide a magnetic recording / reproducing apparatus provided with a recording medium.

As a result of intensive studies to solve the above problems, the present inventor has found that CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ having a small surface energy on a soft magnetic underlayer having an amorphous or microcrystalline structure. Forming a first seed layer containing any one or more selected from the group consisting of TaC, ZrC, and having an fcc structure or hcp structure having a relatively low melting point and a large surface energy on the surface thereof. By forming the second seed layer made of the metal having, the generation of initial nuclei of the second seed layer is not affected by the crystal grains constituting the soft magnetic underlayer and the first seed layer. The inventors have found that the crystal grains constituting the second seed layer are fine and homogeneous. Then, the columnar crystals of each layer grown continuously in the thickness direction from the orientation control layer to the uppermost layer of the perpendicular magnetic layer starting from the second seed layer have a fine and uniform grain size. It has been found that it can be constituted by crystal grains. In addition, the seed layer of the present invention can be reduced in film thickness as compared with a conventionally used NiW alloy layer, thereby reducing the distance between the perpendicular magnetic layer and the soft magnetic underlayer, and the magnetic recording medium. The present inventors have found that the recording characteristics (OW) can be improved, and have completed the present invention.
As a prior application related to the present invention, there is Japanese Patent Application No. 2011-110354.

That is, the present invention provides the following means.
(1) A magnetic recording medium having at least a configuration in which a soft magnetic underlayer, a seed layer, an orientation control layer, and a perpendicular magnetic layer are stacked in this order on a nonmagnetic substrate, The underlayer has an amorphous or microcrystalline structure, and the seed layer includes one or more selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC. A first seed layer; and a second seed layer made of metal formed in an island shape or a net shape on the first seed layer. The orientation control layer and the perpendicular magnetic layer start from the second seed layer. Each of the crystal grains constitutes a columnar crystal that is continuous in the thickness direction.
(2) The magnetic recording medium according to (1), wherein the film thickness of the first seed layer is in the range of 0.3 nm to 2 nm.
(3) The magnetic recording medium according to (1) or (2), wherein the second seed layer includes one or more selected from the group consisting of Cu, Au, and Ag. .
(4) The magnetic recording medium according to any one of (1) to (3), wherein the second seed layer contains Au or Ag.
(5) The orientation control layer includes any one or two or more selected from the group consisting of Ru, Ru alloys, and CoCr alloys, according to any one of (1) to (4), The magnetic recording medium described.
(6) The magnetic recording medium according to (5), wherein the orientation control layer includes Ru.
(7) A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to any one of (1) to (5); and a magnetic head for recording / reproducing information with respect to the magnetic recording medium.

  As described above, in the present invention, the seed layer includes the specific first and second seed layers, so that the top layer of the perpendicular magnetic layer from the orientation control layer starts from the second seed layer. The columnar crystals of each layer that are continuously grown in the thickness direction up to the thickness can be constituted by crystal grains having a fine and uniform grain size, and the seed layer can be made thin. As a result, it is possible to provide a magnetic recording medium capable of maintaining a high perpendicular orientation of the perpendicular magnetic layer and further increasing the recording density, and a magnetic recording / reproducing apparatus including such a magnetic recording medium. is there.

It is sectional drawing which shows the state which the columnar crystal of each layer grew perpendicularly | vertically with respect to the substrate surface. It is sectional drawing which shows typically the characteristic part of the magnetic recording medium to which this invention is applied. It is sectional drawing which shows an example of the magnetic recording medium to which this invention is applied. It is sectional drawing which expands and shows the laminated structure of a magnetic layer and a nonmagnetic layer. It is a perspective view which shows an example of a magnetic recording / reproducing apparatus. It is an AFM image of the sample surface of an Example. It is an AFM image of the sample surface of an Example. It is an AFM image of the sample surface of an Example.

  Hereinafter, a magnetic recording medium and a magnetic recording / reproducing apparatus to which the present invention is applied will be described in detail with reference to the drawings. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Make it not exist.

  As a result of intensive studies to solve the above problems, the present inventor has improved the vertical orientation of the multilayered magnetic layer, and further refined the magnetic particles and homogenized the crystal grain size. Clarified that it is necessary to refine the crystal grains constituting the orientation control layer and to homogenize the crystal grain size.

  That is, as shown in FIG. 1, the orientation control layer 11 is provided with an uneven surface 11a having a dome-shaped convex portion at the top of each columnar crystal S constituting the orientation control layer 11, and the thickness from the uneven surface 11a is increased. The crystal grains of the magnetic layer (or nonmagnetic layer) 12 grow in the direction as columnar crystals S1. The crystal grains of the nonmagnetic layer (or magnetic layer) 13 and the uppermost magnetic layer 14 formed on the columnar crystal S1 also grow epitaxially as columnar crystals S2 and S3 continuous with the columnar crystal S1.

  Thus, when the magnetic layers (layers 12 to 14) are multilayered, the crystal grains constituting each of the layers 12 to 14 are continuous columnar crystals S1 to S1 from the orientation control layer 11 to the uppermost magnetic layer 14. In S3, the epitaxial growth is repeated. Note that the layer 13 illustrated in FIG. 1 is a layer having a granular structure, and an oxide 15 is formed around the columnar crystal S <b> 2 forming the layer 13.

  Therefore, if the crystal grains of the orientation control layer 11 are refined and the crystal grain size is homogenized, each columnar crystal S constituting the orientation control layer 11 is densified, and further, from the top of each columnar crystal S. It is also possible to increase the density of the columnar crystals S1 to S3 of the layers 12 to 14 that grow in a columnar shape in the thickness direction.

As a result of further studies based on such knowledge, the present inventor has, as a result, a soft magnetic underlayer, a seed layer, an orientation control layer, and a perpendicular magnetic layer on at least a nonmagnetic substrate. In the magnetic recording media stacked in this order, the soft magnetic underlayer has an amorphous or microcrystalline structure, and the seed layer is any one selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC. Or a second seed layer made of metal formed in an island shape or a net shape on the first seed layer. It has been found that the columnar crystals of each layer grown continuously in the thickness direction from the orientation control layer to the uppermost layer of the perpendicular magnetic layer can be constituted by crystal grains having a fine and uniform grain size.

  That is, the second seed layer in the present invention is composed of crystal particles having a fine and uniform grain size by the metal formed in an island shape or a net shape, and the orientation is started from the second seed layer. When columnar crystals continuous in the thickness direction from the control layer to the uppermost layer of the perpendicular magnetic layer are grown, the columnar crystals of each layer can be constituted by crystal grains having a fine and uniform grain size.

In the present invention, “island shape” refers to a state in which a plurality of island structures (for example, convex structures constituting the second seed layer 32 in FIG. 2) are formed independently of each other. In FIG. 2, adjacent island structures are formed to be separated from each other on the left and right. The island-shaped structures can be formed so as to be independent from each other not only in the left-right direction but also in other directions within the plane of the first seed layer (for example, a direction perpendicular to the paper surface). “Independent” is not limited to the state of being separated from each other, but also includes the state of being in contact with each other without being integrated with each other.
The cross-sectional shape of the island-shaped structure (the cross-sectional shape perpendicular to the surface of the first seed layer 31) is a semi-elliptical shape in FIG. 2, but is not limited thereto, and is not limited to a semi-circle, semi-oval, It may be a fixed shape.
The shape of the island structure in plan view may be a circle, an ellipse, an indefinite shape, or the like. It is preferable that the island-like structures are formed independently of each other even in a plan view. The island-like structures may be dispersed and scattered in a plan view, or may be overlapped.
“Reticulated” means a state in which at least some of the island-like structures are partially integrated with each other. For example, the network structure may have a structure including a plurality of aggregates in which a plurality of island structures are connected to each other. The network structure may have one or a plurality of isolated void portions (portions where the first seed layer is exposed) surrounded by a plurality of island-shaped structures that are partially connected to each other.
The network structure is, for example, a structure that is formed at a stage where the deposition proceeds further after a plurality of island-like structures are formed in the process of depositing metal on the first seed layer. It is preferable that the net-like structure is made into a net-like structure in a state where the original shape can be recognized in the portion that was an island-like structure.
Whether the first seed layer is island-like or net-like can be confirmed by, for example, an atomic force microscope (AFM) (see FIGS. 7 and 8).

  Thereby, in the present invention, it is possible to provide a magnetic recording medium capable of maintaining a high perpendicular orientation of the perpendicular magnetic layer and further increasing the recording density.

Hereinafter, the characteristic part of the magnetic recording medium to which the present invention is applied will be described in more detail with reference to FIG.
In the magnetic recording medium to which the present invention is applied, as schematically shown in FIG. 2, the soft magnetic underlayer 30 formed on a nonmagnetic substrate (not shown) has an amorphous or microcrystalline structure. The smoothness of the surface 30a of the soft magnetic underlayer 30 is enhanced, and the smoothness of the surface 31a of the first seed layer 31 formed thereon is also enhanced. Further, the first seed layer 31 includes one or more selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC, so that the surface 31 a is smooth. It is possible to increase the sex.

  In the present invention, a second seed layer 32 made of metal formed in an island shape or a net shape is formed on the first seed layer 31. As described above, since the smoothness of the surface 31a of the first seed layer 31 is enhanced, the generation probability of the initial growth nucleus of the metal (second seed layer 32) formed thereon is made uniform. Can do. Thereby, the crystal grains constituting the second seed layer 32 become fine and homogeneous. The second seed layer 32 of the present invention is preferably formed in an island shape from the viewpoint of further homogenizing the distribution of growth nuclei of the orientation control layer 33.

In the present invention, the first seed layer 31 is selected from one or more selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC having a small surface energy. The second seed layer 32 formed thereon is formed with a film having a relatively low melting point and a metal having an fcc structure or hcp structure having a large surface energy so as not to be a continuous film. Thus, crystals of the metal (second seed layer 32) can be formed in an island shape or a net shape. Further, the crystal grain size of this metal is uniform.

For the first seed layer 31, any one or more selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC is used, and among these, CeO ₂ or It is preferable to use Y ₂ O ₃ . Further, when the first seed layer 31 is formed, a sputtering method or the like can be used.

In the present invention, the surface energy of the first seed layer 31 is reduced by using any one or more selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC. In addition, the smoothness of the surface 31a can be enhanced. Further, by flattening the surface of the first seed layer 31, the second seed layer 32 formed thereon has a uniform nucleus generation density, and the nucleus is the first seed layer. It refines by the surface energy difference with 31. That is, as shown in FIG. 2, the crystal grains constituting the first seed layer 31 and the crystal grains constituting the second seed layer 32 are not necessarily epitaxially grown corresponding to 1: 1. The nucleation density of crystal grains constituting the seed layer 32 can be equal to or higher than that of the crystal grains constituting the first seed layer 31.

The film thickness of the first seed layer 31 is preferably in the range of 0.3 nm to 2 nm, more preferably 0.3 nm to 1 nm, and most preferably 0.3 nm to 0.5 nm. . By setting the film thickness of the first seed layer 31 within the above range, the surface smoothness after the film formation can be improved.
The reason why the surface smoothness is increased by controlling the film thickness of the first seed layer 31 is that the above substance is an amorphous material or a crystal-growing material. This is because the surface is flattened.
Note that the first seed layer includes not only a continuous film but also an island shape (island shape). This is because even when the first seed layer is island-shaped, the film thickness is thin, so that the growth surface can be flattened. In addition, the said film thickness in the case of island shape is calculated as an average film thickness.

  For the second seed layer 32, it is preferable to use a metal containing one or more selected from the group consisting of Cu, Au, and Ag, and in particular, it is preferable to use Au or Ag. . Such a metal easily aligns the c-plane and has a large surface energy, so that it is easy to form fine and uniform island-like or net-like crystals. Further, when the second seed layer 32 is formed, a sputtering method or the like can be used. However, in order to make the second seed layer 32 into an island shape or a net shape, the film formation time is shortened. It is necessary to prevent the second seed layer 32 from becoming a continuous film.

  In the present invention, the orientation control layer 33 is formed on the second seed layer 32. For the orientation control layer 33, it is preferable to use one or two or more selected from the group consisting of Ru, Ru alloys, and CoCr alloys, and it is particularly preferable to use Ru. Thereby, the crystal grains constituting the orientation control layer 33 are epitaxially grown as columnar crystals continuous in the thickness direction while corresponding 1: 1 with the crystal grains constituting the second seed layer 32.

  In addition, since a dome-shaped convex portion 33a is formed at a portion including the top of each columnar crystal constituting the orientation control layer 33, a perpendicular magnetic layer (not shown) formed on the convex portion 33a is formed. The crystal grains can be epitaxially grown to form columnar crystals that are continuous in the thickness direction.

  The average particle diameter of the crystal grains constituting the orientation control layer 33 is preferably 6 nm or less, more preferably 4 nm or less. Crystal grains constituting the conventional orientation control layer have an average particle size of about 7 to 9 nm. On the other hand, in this invention, the average particle diameter of the crystal grain which comprises the orientation control layer 33 can be 6 nm or less. Thereby, in the present invention, the magnetic particle density of the magnetic recording medium can be increased by 2 times or more, and as a result, the recording density of the magnetic recording medium can be increased by 2 times or more.

FIG. 3 shows an example of a magnetic recording medium to which the present invention is applied.
As shown in FIG. 3, the magnetic recording medium includes a soft magnetic underlayer 2, a seed layer 9, an orientation control layer 3, a perpendicular magnetic layer 4, a protective layer 5, and a nonmagnetic substrate 1. The lubricating layer 6 is sequentially laminated.

  The perpendicular magnetic layer 4 includes, from the nonmagnetic substrate 1 side, three layers of a lower magnetic layer 4a, an intermediate magnetic layer 4b, and an upper magnetic layer 4c, and between the magnetic layer 4a and the magnetic layer 4b. By including the upper nonmagnetic layer 7b between the lower nonmagnetic layer 7a and the magnetic layer 4b and the magnetic layer 4c, the magnetic layers 4a to 4c and the nonmagnetic layers 7a and 7b are alternately stacked. It has a structure.

  Further, although not shown, the crystal grains constituting each of the magnetic layers 4 a to 4 c and the nonmagnetic layers 7 a and 7 b form columnar crystals continuous in the thickness direction together with the crystal grains constituting the orientation control layer 3. Yes.

  As the nonmagnetic substrate 1, for example, a metal substrate made of a metal material such as aluminum or an aluminum alloy may be used. For example, a nonmetal substrate made of a nonmetal material such as glass, ceramic, silicon, silicon carbide, or carbon. May be used. In addition, it is also possible to use a substrate in which a NiP layer or a NiP alloy layer is formed on the surface of the metal substrate or nonmetal substrate by using, for example, a plating method or a sputtering method.

  As the glass substrate, for example, amorphous glass or crystallized glass can be used, and as the amorphous glass, for example, general-purpose soda lime glass or aluminosilicate glass can be used. In addition, as the crystallized glass, for example, lithium-based crystallized glass can be used. As the ceramic substrate, for example, general-purpose aluminum oxide, a sintered body mainly composed of aluminum nitride, silicon nitride, or the like, or a fiber reinforced material thereof can be used.

  The nonmagnetic substrate 1 preferably has an average surface roughness (Ra) of 2 nm (20 mm) or less, preferably 1 nm or less from the viewpoint of suitable for high recording density recording with a magnetic head flying low. Further, it is preferable that the surface fine waviness (Wa) is 0.3 nm or less (more preferably 0.25 nm or less) from the viewpoint of being suitable for high recording density recording with the magnetic head flying low. In addition, it is possible to use a magnetic head having a chamfered portion at the end face and a surface average roughness (Ra) of at least one of the side surface portion of 10 nm or less (more preferably 9.5 nm or less). Preferred for stability. In addition, microwaviness (Wa) can be measured as surface average roughness in a measuring range of 80 μm using, for example, a surface roughness measuring device P-12 (manufactured by KLM-Tencor).

  Further, when the nonmagnetic substrate 1 is in contact with the soft magnetic underlayer 2 mainly composed of Co or Fe, there is a possibility that the corrosion progresses due to the adsorption gas on the surface, the influence of moisture, the diffusion of the substrate components, and the like. is there. In this case, it is preferable to provide an adhesion layer between the nonmagnetic substrate 1 and the soft magnetic underlayer 2, thereby suppressing these. In addition, as a material of the adhesion layer, for example, Cr, Cr alloy, Ti, Ti alloy, or the like can be selected as appropriate. The thickness of the adhesion layer is preferably 2 nm (20 mm) or more.

  The soft magnetic underlayer 2 is used to increase the direction component of the magnetic flux generated from the magnetic head in the direction perpendicular to the substrate surface, and to make the direction of magnetization of the perpendicular magnetic layer 4 on which information is recorded stronger than the nonmagnetic substrate 1. It is provided for fixing in the vertical direction. This effect becomes more conspicuous particularly when a single pole head for perpendicular recording is used as a magnetic head for recording and reproduction.

  As the soft magnetic underlayer 2, for example, an amorphous or microcrystalline soft magnetic material containing Fe, Ni, Co, or the like can be used. Specific examples of soft magnetic materials include CoFe alloys (CoFeTaZr, CoFeZrNb, etc.), FeCo alloys (FeCo, FeCoV, etc.), FeNi alloys (FeNi, FeNiMo, FeNiCr, FeNiSi, etc.), and FeAl. Alloys (FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, FeAlO, etc.), FeCr alloys (FeCr, FeCrTi, FeCrCu, etc.), FeTa alloys (FeTa, FeTaC, FeTaN, etc.), FeMg alloys (FeMgO, etc.), Examples thereof include FeZr alloys (FeZrN, etc.), FeC alloys, FeN alloys, FeSi alloys, FeP alloys, FeNb alloys, FeHf alloys, FeB alloys, and the like.

  In addition, as the soft magnetic underlayer 2, a Co alloy containing 80 at% or more of Co, containing at least one of Zr, Nb, Ta, Cr, Mo and the like and having an amorphous or microcrystalline structure is used. be able to. Specific examples of the specific material include CoZr, CoZrNb, CoZrTa, CoZrCr, and CoZrMo-based alloys.

  The soft magnetic underlayer 2 is composed of two soft magnetic films, and a Ru film is preferably provided between the two soft magnetic films. By adjusting the thickness of the Ru film within a range of 0.4 to 1.0 nm or 1.6 to 2.6 nm, the two-layer soft magnetic film has an AFC structure. By adopting such an AFC structure, so-called spike noise can be suppressed.

  Since the seed layer 9 and the orientation control layer 3 can be formed by sequentially stacking the first seed layer 31, the second seed layer 32, and the orientation control layer 33 shown in FIG. 2, the description thereof is omitted. Shall.

  Further, it is preferable to provide a nonmagnetic underlayer 8 between the orientation control layer 3 and the perpendicular magnetic layer 4. In the initial part of the perpendicular magnetic layer 4 immediately above the orientation control layer 3, disorder of crystal growth is likely to occur, which causes noise. The occurrence of noise can be suppressed by replacing the disturbed portion of the initial portion with the nonmagnetic underlayer 8.

The nonmagnetic underlayer 8 is preferably made of a material mainly containing Co and further containing an oxide. As the oxide, for example, oxides such as Cr, Si, Ta, Al, Ti, Mg, and Co are preferably used, and among them, TiO ₂ , Cr ₂ O ₃ , SiO _{2, and the} like are preferably used. it can. The content of the oxide is preferably 3 mol% or more and 18 mol% or less with respect to the total amount of mol calculated as one compound, for example, an alloy such as Co, Cr, and Pt constituting the magnetic particles.

The nonmagnetic underlayer 8 is preferably made of a complex oxide to which two or more kinds of oxides are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , Cr ₂ O ₃ —SiO ₂ —TiO _{2 and the} like can be preferably used. Furthermore, CoCr—SiO ₂ , CoCr—TiO ₂ , CoCr—Cr ₂ O ₃ —SiO ₂ , CoCr—TiO ₂ —Cr ₂ O ₃ , CoCr—Cr ₂ O ₃ —TiO ₂ —SiO ₂ or the like is preferably used. Can do. Further, Pt may be added from the viewpoint of crystal growth.

  The thickness of the nonmagnetic underlayer 8 is preferably 0.2 nm or more and 3 nm or less. If the thickness exceeds 3 nm, Hc and Hn decrease, which is not preferable.

The magnetic layer 4a is made of a material mainly containing Co and further containing an oxide. As this oxide, for example, an oxide such as Cr, Si, Ta, Al, Ti, Mg, Co is preferably used. . Among _{them, TiO 2, Cr 2 O 3} , SiO ₂ or the like can be suitably used. The magnetic layer 4a is preferably made of a complex oxide to which two or more kinds of oxides are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , Cr ₂ O ₃ —SiO ₂ —TiO _{2 and the} like can be preferably used.

  As shown in FIG. 4, in the magnetic layer 4 a, it is preferable that magnetic particles (magnetized crystal particles) 42 are dispersed in a layer including the oxide 41. The magnetic particles 42 preferably have a columnar structure that vertically penetrates the magnetic layers 4a and 4b and further the magnetic layer 4c. By having such a structure, the orientation and crystallinity of the magnetic particles 42 of the magnetic layer 4a are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. .

  In order to obtain such a structure, the amount of the oxide 41 to be contained and the film formation conditions of the magnetic layer 4a are important. That is, the content of the oxide 41 is 3 mol% or more and 18 mol% or less with respect to the total mol amount of the magnetic particles 42, for example, an alloy such as Co, Cr, and Pt calculated as one compound. preferable. More preferably, it is 6 mol% or more and 13 mol% or less.

  The above range is preferable as the content of the oxide 41 in the magnetic layer 4a. When the magnetic layer 4a is formed, the oxide 41 is precipitated around the magnetic particles 42, and the magnetic particles 42 are isolated and refined. This is because it becomes possible. On the other hand, when the content of the oxide 41 exceeds the above range, the oxide 41 remains in the magnetic particle 42, impairs the orientation and crystallinity of the magnetic particle 42, and further above and below the magnetic particle 42. The oxide 41 is deposited, and as a result, a columnar structure in which the magnetic particles 42 penetrate through the magnetic layers 4a to 4c is not formed. In addition, when the content of the oxide 41 is less than the above range, separation and refinement of the magnetic particles 42 are insufficient, resulting in an increase in noise during recording and reproduction, and a signal / This is not preferable because the noise ratio (S / N ratio) cannot be obtained.

  The content of Cr in the magnetic layer 4a is preferably 20 at% or less (more preferably 6 at% or more and 16 at% or less). The reason why the Cr content is in the above range is that the magnetic anisotropy constant Ku of the magnetic particles 42 is not lowered too much, and high magnetization is maintained. As a result, recording / reproduction characteristics suitable for high-density recording and sufficient heat This is because fluctuation characteristics can be obtained.

  On the other hand, when the Cr content exceeds the above range, the magnetic anisotropy constant Ku of the magnetic particles 42 becomes small, so that the thermal fluctuation characteristics deteriorate, and the crystallinity and orientation of the magnetic particles 42 deteriorate. As a result, the recording / reproduction characteristics deteriorate, which is not preferable. Further, when the Cr content is less than the above range, the magnetic anisotropy constant Ku of the magnetic particles 42 is high, so that the perpendicular coercive force becomes too high and data is sufficiently written by a magnetic head when data is recorded. This is not preferable because the recording characteristics (OW) are unsuitable for high density recording.

  The content of Pt in the magnetic layer 4a is preferably 8 at% or more and 25 at% or less. The reason why the Pt content is within the above range is that the magnetic anisotropy constant Ku required for the perpendicular magnetic layer 4 is low when it is less than 8 at%. On the other hand, if it exceeds 25 at%, a stacking fault is generated inside the magnetic particle 42, and as a result, the magnetic anisotropy constant Ku is lowered. Therefore, in order to obtain thermal fluctuation characteristics and recording / reproduction characteristics suitable for high-density recording, the Pt content is preferably set in the above range.

  In addition, when the Pt content exceeds the above range, an fcc structure layer is formed in the magnetic particles 42, and the crystallinity and orientation may be impaired. On the other hand, if the Pt content is less than the above range, the magnetic anisotropy constant Ku for obtaining thermal fluctuation characteristics suitable for high-density recording cannot be obtained.

  In addition to Co, Cr, Pt and oxide 41, the magnetic layer 4a contains one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re. Can be included. By including the above elements, the miniaturization of the magnetic particles 42 can be promoted or the crystallinity and orientation can be improved, and recording / reproduction characteristics and thermal fluctuation characteristics suitable for higher density recording can be obtained.

  Further, the total content of the above elements is preferably 8 at% or less. If it exceeds 8 at%, a phase other than the hcp phase is formed in the magnetic particles 42, so that the crystallinity and orientation of the magnetic particles 42 are disturbed, resulting in recording / reproducing characteristics and thermal fluctuation characteristics suitable for high-density recording. Is not preferred because it cannot be obtained.

As a material suitable for the magnetic layer 4a, for example, 90 (Co14Cr18Pt) -10 (SiO ₂ ) {Cr content 14at%, Pt content 18at%, molar concentration calculated as one compound with magnetic particles composed of the remaining Co. Is 90 mol%, the oxide composition of SiO ₂ is 10 mol%}, 92 (Co10Cr16Pt) -8 (SiO ₂ ), 94 (Co8Cr14Pt4Nb) -6 (Cr ₂ O ₃ ), and (CoCrPt)-(Ta ₂ O _{5), (CoCrPt) - (} Cr 2 O 3) - (TiO 2), (CoCrPt) - (Cr 2 O 3) - (SiO 2), (CoCrPt) - (Cr 2 O 3) - (SiO 2) _{- (TiO 2), (CoCrPtMo} ) - (TiO), (CoCrPtW) - (TiO 2), (CoCrPtB) - (Al 2 Examples thereof include compositions such as (O ₃ ), (CoCrPtTaNd)-(MgO), (CoCrPtBCu)-(Y ₂ O ₃ ), (CoCrPtRu)-(SiO ₂ ).

  Since the magnetic layer 4b can be made of the same material as the magnetic layer 4a, the description thereof will be omitted. In the magnetic layer 4b, it is preferable that magnetic particles (crystal grains having magnetism) 42 are dispersed in the layer. As shown in FIG. 4, the magnetic particles 42 preferably have a columnar structure that vertically penetrates the magnetic layers 4a and 4b and further the magnetic layer 4c. By forming such a structure, the orientation and crystallinity of the magnetic particles 42 of the magnetic layer 4b are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. it can.

  The magnetic layer 4c is preferably made of a material that contains Co as a main component and does not contain an oxide. As shown in FIG. 4, the magnetic particles 42 in the layer form columnar shapes from the magnetic particles 42 in the magnetic layer 4a. The structure is preferably epitaxially grown. In this case, the magnetic particles 42 of the magnetic layers 4a to 4c are preferably epitaxially grown in a columnar shape in a one-to-one correspondence in each layer. Further, the magnetic particles 42 of the magnetic layer 4b are epitaxially grown from the magnetic particles 42 in the magnetic layer 4a, so that the magnetic particles 42 of the magnetic layer 4b are miniaturized and the crystallinity and orientation are further improved. Become.

  The content of Cr in the magnetic layer 4c is preferably 10 at% or more and 24 at% or less. By setting the Cr content in the above range, a sufficient output during data reproduction can be ensured, and even better thermal fluctuation characteristics can be obtained. On the other hand, when the content of Cr exceeds the above range, the magnetization of the magnetic layer 4c becomes too small, which is not preferable. When the Cr content is less than the above range, the magnetic particles 42 are not sufficiently separated and refined, noise during recording / reproduction increases, and a signal / noise ratio (S) suitable for high-density recording (S / N ratio) is not obtained.

  The magnetic layer 4c may be made of a material containing Pt in addition to Co and Cr. The Pt content in the magnetic layer 4c is preferably 6 at% or more and 20 at% or less. When the Pt content is in the above range, a sufficient coercive force suitable for high recording density can be obtained, and a high reproduction output during recording and reproduction can be maintained, resulting in recording suitable for high density recording. Reproduction characteristics and thermal fluctuation characteristics can be obtained.

  On the other hand, when the content of Pt exceeds the above range, an fcc-structured phase is formed in the magnetic layer 4c, which is not preferable because the crystallinity and orientation may be impaired. On the other hand, if the Pt content is less than the above range, the magnetic anisotropy constant Ku for obtaining thermal fluctuation characteristics suitable for high-density recording cannot be obtained.

  The magnetic layer 4c contains one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt. Can do. By including the above elements, the miniaturization of the magnetic particles 42 can be promoted or crystallinity and orientation can be improved, and recording / reproduction characteristics and thermal fluctuation characteristics suitable for higher density recording can be obtained.

  The total content of the above elements is preferably 16 at% or less. On the other hand, if it exceeds 16 at%, a phase other than the hcp phase is formed in the magnetic particles 42, so that the crystallinity and orientation of the magnetic particles 42 are disturbed, resulting in recording / reproduction characteristics suitable for high-density recording. This is not preferable because thermal fluctuation characteristics cannot be obtained.

  Examples of suitable materials for the magnetic layer 4c include CoCrPt and CoCrPtB. In the case of the CoCrPtB system, the total content of Cr and B is preferably 18 at% or more and 28 at% or less.

  Suitable materials for the magnetic layer 4c include, for example, Co14-24Cr8-22Pt {Cr content 14-24at%, Pt content 8-22at%, balance Co} in CoCrPt series, Co10-24Cr8 ~ in CoCrPtB series. 22Pt0-16B {Cr content: 10-24at%, Pt content: 8-22at%, B content: 0-16at%, balance Co} is preferable. In other systems, Co10-24Cr8-22Pt1-5Ta {Cr content 10-24at%, Pt content 8-22at%, Ta content 1-5at%, balance Co} in CoCrPtTa system, Co10 in CoCrPtTaB system -24Cr8-22Pt1-5Ta1-10B {Cr content 10-24at%, Pt content 8-22at%, Ta content 1-5at%, B content 1-10at%, balance Co}, CoCrPtBNd Examples thereof include materials such as a CoCrPtTaNd system, a CoCrPtNb system, a CoCrPtBW system, a CoCrPtMo system, a CoCrPtCuRu system, and a CoCrPtRe system.

  The perpendicular coercive force (Hc) of the perpendicular magnetic layer 4 is preferably 3000 [Oe] or more. When the coercive force is less than 3000 [Oe], the recording / reproducing characteristics, particularly the frequency characteristics, are deteriorated, and the thermal fluctuation characteristics are also deteriorated, which is not preferable as a high-density recording medium.

  The reverse magnetic domain nucleation magnetic field (-Hn) of the perpendicular magnetic layer 4 is preferably 1500 [Oe] or more. When the reverse domain nucleation magnetic field (-Hn) is less than 1500 [Oe], the thermal fluctuation resistance is poor, which is not preferable.

  The perpendicular magnetic layer 4 preferably has an average particle diameter of magnetic particles of 3 to 12 nm. This average particle diameter can be obtained, for example, by observing the perpendicular magnetic layer 4 with a TEM (transmission electron microscope) and image-processing the observed image.

  The thickness of the perpendicular magnetic layer 4 is preferably 5 to 20 nm. If the thickness of the perpendicular magnetic layer 4 is less than the above, sufficient reproduction output cannot be obtained, and the thermal fluctuation characteristics also deteriorate. When the thickness of the perpendicular magnetic layer 4 exceeds the above range, the magnetic particles in the perpendicular magnetic layer 4 are enlarged, increasing noise during recording and reproduction, and a signal / noise ratio (S / N). Ratio) and recording / reproducing characteristics represented by recording characteristics (OW) are not preferable.

The protective layer 5 is for preventing corrosion of the perpendicular magnetic layer 4 and preventing damage to the surface of the medium when the magnetic head comes into contact with the medium, and a conventionally known material can be used, for example, C, SiO ₂ and those containing ZrO ₂ can be used. The thickness of the protective layer 5 is preferably 1 to 10 nm from the viewpoint of high recording density because the distance between the head and the medium can be reduced.

  For the lubricating layer 6, it is preferable to use a lubricant such as perfluoropolyether, fluorinated alcohol, fluorinated carboxylic acid, or the like.

  In the present invention, the magnetic layer on the nonmagnetic substrate 1 side is preferably a granular magnetic layer, and the magnetic layer on the protective layer 5 side is preferably a non-granular magnetic layer containing no oxide. With this configuration, it is possible to more easily control and adjust each characteristic such as the thermal fluctuation characteristic, recording characteristic (OW), and S / N ratio of the magnetic recording medium.

  In the present invention, the perpendicular magnetic layer 4 can be composed of four or more magnetic layers. For example, in addition to the magnetic layers 4a and 4b, a magnetic layer having a granular structure is composed of three layers, and a magnetic layer 4c not containing an oxide is provided thereon, and a magnetic layer not containing an oxide is also provided. The layer 4c may have a two-layer structure and be provided on the magnetic layers 4a and 4b.

  In the present invention, it is preferable to provide a nonmagnetic layer 7 (indicated by reference numerals 7a and 7b in FIG. 4) between three or more magnetic layers constituting the perpendicular magnetic layer 4. By providing the nonmagnetic layer 7 with an appropriate thickness, magnetization reversal of individual films can be facilitated, and dispersion of magnetization reversal of the entire magnetic particles can be reduced. As a result, the S / N ratio can be further improved.

  As the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, it is preferable to use a material having an hcp structure. Specifically, for example, Ru, Ru alloy, CoCr alloy, CoCrX1 alloy (X1 is Pt, Ta, Zr, Re, Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W, Mo, Mo. , Ti, V, Zr, or B represents at least one element or two or more elements).

  When a CoCr-based alloy is used as the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, the Co content is preferably in the range of 30 to 80 at%. This is because within this range, the coupling between the magnetic layers can be adjusted to be small.

  Further, as the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, as an alloy having an hcp structure, an alloy such as Ru, Re, Ti, Y, Hf, Zn, or the like can be used other than Ru. .

  Further, as the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, metals or alloys having other structures may be used as long as the crystallinity and orientation of the upper and lower magnetic layers are not impaired. it can. Specifically, for example, Pd, Pt, Cu, Ag, Au, Ir, Mo, W, Ta, Nb, V, Bi, Sn, Si, Al, C, B, Cr, or an alloy thereof is used. it can. In particular, as a Cr alloy, CrX2 (X2 represents at least one element selected from Ti, W, Mo, Nb, Ta, Si, Al, B, C, and Zr) or the like. Can be suitably used. In this case, the Cr content is preferably 60 at% or more.

As the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, it is preferable to use a layer having a structure in which metal particles of the above alloy are dispersed in an oxide, a metal nitride, or a metal carbide. Further, it is more preferable that the metal particles have a columnar structure penetrating the nonmagnetic layer 7 vertically. In order to obtain such a structure, it is preferable to use an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, as the oxide, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , TiO _2, etc. As the metal nitride, for example, AlN, Si For example, TaC, BC, SiC, or the like can be used as the metal carbide such as ₃ N ₄ , TaN, or CrN. Furthermore, for example, CoCr—SiO ₂ , CoCr—TiO ₂ , CoCr—Cr ₂ O ₃ , CoCrPt—Ta ₂ O ₅ , Ru—SiO ₂ , Ru—Si ₃ N ₄ , Pd—TaC, and the like can be used.

  The content of the oxide, metal nitride, or metal carbide in the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4 is a content that does not impair the crystal growth and crystal orientation of the perpendicular magnetic film. Is preferred. In addition, the content of oxide, metal nitride, or metal carbide is preferably 4 mol% or more and 30 mol% or less with respect to the alloy.

  When the content of the oxide, metal nitride, or metal carbide in the nonmagnetic layer 7 exceeds the above range, the oxide, metal nitride, or metal carbide remains in the metal particle, and the metal particle In addition to impairing crystallinity and orientation, oxides, metal nitrides, or metal carbides are also deposited on the top and bottom of the metal particles, making it difficult for the metal particles to have a columnar structure that vertically penetrates the nonmagnetic layer 7. This is not preferable because the crystallinity and orientation of the magnetic layer formed on the magnetic layer 7 may be impaired. On the other hand, when the content of the oxide, metal nitride, or metal carbide in the nonmagnetic layer 7 is less than the above range, the effect of adding the oxide, metal nitride, or metal carbide cannot be obtained. Therefore, it is not preferable.

FIG. 5 shows an example of a magnetic recording / reproducing apparatus to which the present invention is applied.
This magnetic recording / reproducing apparatus includes a magnetic recording medium 50 having the configuration shown in FIG. 3, a medium driving unit 51 that rotationally drives the magnetic recording medium 50, a magnetic head 52 that records and reproduces information on the magnetic recording medium 50, A head driving unit 53 that moves the magnetic head 52 relative to the magnetic recording medium 50 and a recording / reproducing signal processing system 54 are provided. Further, the recording / reproducing signal processing system 54 can process data input from the outside and send a recording signal to the magnetic head 52, process a reproducing signal from the magnetic head 52, and send the data to the outside. ing. Further, as the magnetic head 52 used in the magnetic recording / reproducing apparatus to which the present invention is applied, a magnetic head suitable for a higher recording density having a GMR element utilizing a giant magnetoresistance effect (GMR) as a reproducing element is used. be able to.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

(Examples 1-9)
In Examples 1 to 9, first, a cleaned glass substrate (manufactured by Konica Minolta, Inc., 2.5 inches in outer diameter) is accommodated in a film forming chamber of a DC magnetron sputtering apparatus (C-3040 manufactured by Anelva). After evacuating the inside of the film formation chamber until the ultimate vacuum reached 1 × 10 ⁻⁵ Pa, an adhesion layer having a thickness of 10 nm was formed on the glass substrate using a Cr target. Moreover, on this adhesion layer, the substrate temperature is set to 100 ° C. or less, and a target of Co-20Fe-5Zr-5Ta {Fe content 20 at%, Zr content 5 at%, Ta content 5 at%, balance Co} is used. Then, after forming a soft magnetic layer having a layer thickness of 25 nm and forming a Ru layer having a layer thickness of 0.7 nm thereon, a Co-20Fe-5Zr-5Ta target is again used to form a soft magnetic layer having a layer thickness of 25 nm. A magnetic layer was formed and used as a soft magnetic underlayer.

Next, a first seed layer and a second seed layer were formed on the soft magnetic underlayer by sputtering using the materials and thicknesses shown in Table 1.
FIG. 6 shows an AFM image of the growth surface of the CeO ₂ layer (first seed layer) having a thickness of 0.5 nm (corresponding to the surface of the first seed layer in Example 1). FIG. 7 shows an AFM image of the growth surface when an Au layer (second seed layer) having a thickness of 0.5 nm is provided on the surface of the CeO ₂ layer (second seed layer of Example 1). Corresponding to the surface.). The Au layer (second seed layer) shown in FIG. 7 is formed in an island shape.
FIG. 8 shows an AFM image of the growth surface when an Au layer (second seed layer) having a thickness of 1 nm is provided on the surface of the CeO ₂ layer formed in the same manner as in Example 1 (Example 9). Corresponding to the surface of the second seed layer). The Au layer (second seed layer) shown in FIG. 8 is formed in a net shape.

  Next, an alignment control layer having a layer thickness of 20 nm was formed on the second seed layer using a Ru target. When forming the orientation control layer, Ru having a thickness of 10 nm was formed at a sputtering pressure of 0.8 Pa, and then Ru having a thickness of 10 nm was formed at a sputtering pressure of 10 Pa.

Next, on the orientation control layer, 91 (Co15Cr18Pt) -6 (SiO ₂ ) -3 (TiO ₂ ) {Cr content of 15 at%, Pt content of 18 at%, and the remaining Co alloy from 91 mol%, SiO ₂ A magnetic layer having a thickness of 9 nm was formed using a target of 6 mol% of an oxide and 3 mol% of an oxide of TiO ₂ . The sputtering pressure at this time was 2 Pa.

Next, on the magnetic _{layer, 88 (Co30Cr) -12 (TiO} 2) {Cr content 30 at%, 88 mol% of the alloy the remainder Co, the oxide of TiO ₂ 12 mol%} using a target of, A nonmagnetic layer having a thickness of 0.3 nm was formed.

Next, on the nonmagnetic layer, 92 (Co11Cr18Pt) -5 (SiO ₂ ) -3 (TiO ₂ ) {Cr content of 11 at%, Pt content of 18 at%, and the remaining Co alloy from 92 mol%, SiO ₂ A magnetic layer having a thickness of 6 nm was formed using a target of 5 mol% of an oxide and 3 mol% of an oxide of TiO ₂ . The sputtering pressure at this time was 2 Pa.

  Next, a nonmagnetic layer having a layer thickness of 0.3 nm was formed on the magnetic layer using a Ru target.

  Next, a 7 nm thick magnetic layer was formed on the nonmagnetic layer using a target of Co20Cr14Pt3B {Cr content 20 at%, Pt content 14 at%, B content 3 at%, balance Co}. The sputtering pressure at this time was 0.6 Pa.

  Next, a protective layer having a thickness of 3.0 nm was formed on the magnetic layer by a CVD method, and then a lubricating film made of perfluoropolyether was formed by a dipping method to obtain a magnetic recording medium.

  For comparison, as shown in Table 1, magnetic recording media were manufactured without forming the first seed layer or the second seed layer (Comparative Examples 1 to 3). The structure other than the seed layer was in accordance with Examples 1-9. In Comparative Example 1, a conventional magnetic recording medium using a NiW seed layer was shown.

For each of these magnetic recording media, “SNR (dB)”, overwrite characteristic “OW (dB)”, and bit error rate “BER” were measured. The measurement results are shown in Table 1. The bit error rate is calculated by “−log (number of error bits / total number of bits)”. The larger the numerical value shown in Table 1, the smaller the bit error of the magnetic recording medium.
As shown in Examples 1 to 9, excellent electromagnetic conversion characteristics are obtained in the magnetic recording medium using the seed layer of the present invention.
In Example 8, since the CeO ₂ layer (first seed layer) is thick (film thickness: 2 nm), the smoothness of the growth surface is slightly deteriorated, whereby the island-like growth of Au is slightly inhibited, and Au ( Variation in the particle size of the second seed layer) occurs. In addition to this, the OW is slightly reduced because the overall seed layer thickness is increased.
Further, in Example 9, the Au layer was thicker than in Examples 1 to 8, so that the Au layer became net growth instead of island growth, and the electromagnetic conversion characteristics of the magnetic recording medium were slightly lowered.
In Comparative Example 3, the Au layer is provided directly on the soft magnetic underlayer. In this case, since the wettability of Au is high, Au has a flat film growth, and the initial Ru layer provided thereon is formed. The effect of making the nuclei uniform cannot be obtained, and the electromagnetic conversion characteristics are greatly deteriorated.

1. Non-magnetic substrate
2. Soft magnetic underlayer
3 ... Orientation control layer
4 ... perpendicular magnetic layer
4a: lower magnetic layer
4b ... middle magnetic layer
4c ... upper magnetic layer
5 ... Protective layer
6 ... Lubrication layer
7 ... Nonmagnetic layer
7a: lower nonmagnetic layer
7b: upper nonmagnetic layer
8 ... Nonmagnetic underlayer
9 ... Seed layer 11 ... Orientation control layer
11a ... uneven surface
12-14: Magnetic layer or nonmagnetic layer
S, S1 to S3 ... columnar crystals
30: Soft magnetic underlayer
31 ... first seed layer
32. Second seed layer
33 ... Orientation control layer
50. Magnetic recording medium
51. Medium drive unit
52. Magnetic head
53. Head drive unit
54. Recording / reproducing signal processing system

Claims (7)

A magnetic recording medium having at least a configuration in which a soft magnetic underlayer, a seed layer, an orientation control layer, and a perpendicular magnetic layer are stacked in this order on a nonmagnetic substrate,
The soft magnetic underlayer has an amorphous or microcrystalline structure,
The seed layer includes a first seed layer including one or more selected from the group consisting of CeO ₂ , Y ₂ O ₃ , Cr ₂ O ₃ , TaC, and ZrC, and an island shape or A second seed layer made of a net-like metal,
The magnetic recording medium, wherein the orientation control layer and the perpendicular magnetic layer form columnar crystals in which respective crystal grains are continuous in the thickness direction starting from the second seed layer. 2. The magnetic recording medium according to claim 1, wherein the film thickness of the first seed layer is in a range of 0.3 nm to 2 nm. The magnetic recording medium according to claim 1, wherein the second seed layer includes one or more selected from the group consisting of Cu, Au, and Ag. The magnetic recording medium according to claim 1, wherein the second seed layer contains Au or Ag. 5. The magnetic recording medium according to claim 1, wherein the orientation control layer includes one or more selected from the group consisting of Ru, Ru alloys, and CoCr alloys. . The magnetic recording medium according to claim 5, wherein the orientation control layer includes Ru. A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to claim 1; and a magnetic head for recording / reproducing information with respect to the magnetic recording medium.