JP2006286106A - Vertical magnetic recording medium and magnetic storage apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical magnetic recording medium which has an excellent S/N ratio and whose recording density is made high, to provide its manufacturing method and to provide a magnetic storage apparatus. <P>SOLUTION: The vertical magnetic recording medium 10 has a substrate 11 and a soft magnetic backing layer 12, an orientation control layer 13, an underlayer 14, an intermediate layer 15, a recording layer 16, a protective layer 20 and a lubrication layer 21 sequentially layered on the substrate 11. The magnetic layer 16 is formed by layering a first magnetic layer 18 and a second magnetic layer 19 sequentially from the intermediate layer 15 side. When tilts in applied magnetization intensities equivalent to coercive force of magnetization curves obtained when magnetic fields are applied to respective substrate surfaces of the first and the second magnetic layers 18 and 19 along their vertical directions are defined as α<SB>1</SB>and α<SB>2</SB>, respectively, and when anisotropic magnetic fields of the first and the second magnetic layers 18 and 19 are defined as H<SB>k1</SB>and H<SB>k2</SB>, respectively, relations of α<SB>1</SB><α<SB>2</SB>and H<SB>k1</SB><H<SB>k2</SB>are satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a perpendicular magnetic recording medium and a magnetic storage device.

  In a magnetic storage device, for example, a hard disk drive (HDD) device, a perpendicular magnetic recording method using a combination of a perpendicular recording head and a two-layer perpendicular magnetic recording medium has been actively studied as a next-generation magnetic recording method.

  The two-layer perpendicular magnetic recording medium has a two-layer magnetic layer composed of a soft magnetic underlayer and a perpendicularly magnetized recording layer on a substrate. As one of the development problems of such a two-layer perpendicular magnetic recording medium, reduction of medium noise generated from each of the soft magnetic underlayer and the recording layer is cited.

  The soft magnetic backing layer is made of a soft magnetic material having a low coercive force. As a medium noise of the soft magnetic underlayer, a magnetic domain is formed in the soft magnetic underlayer, and spike noise generated by the movement of the domain wall of the magnetic domain is a problem. In order to prevent the occurrence of spike noise, for example, a method has been proposed in which a diamagnetic layer or a magnetic layer having a high coercive force is formed adjacent to a soft magnetic backing layer.

On the other hand, with respect to the recording layer, recently, a recording layer having a so-called columnar granular structure in which columnar crystal grains of a CoPt-based alloy are separated by an oxide has attracted attention as being capable of reducing medium noise. In a two-layered perpendicular magnetic recording medium having a recording layer with a columnar granular structure, various improvements such as materials, structures, processes, etc. have been attempted including an intermediate layer serving as a base of the recording layer (for example, Patent Document 1). reference.)
JP 2003-217107 A

  However, various media noise reduction methods have been proposed, but there is a problem that the media noise is not sufficiently reduced by the conventional methods. As the cause, in the recording layer having the granular structure, there is a case where the DC erase noise and the transition noise constituting the medium noise have a tendency to contradict each other with respect to the magnetic characteristics of the recording layer. This is one of the reasons that makes it difficult to reduce medium noise. Note that the DC erase noise is noise generated when a DC magnetic field is applied to the recording layer and magnetized in one direction, and the DC erase noise increases if the magnetic uniformity of the recording layer is inferior. In addition, transition noise is noise that occurs remarkably when recording at a high recording density, and is caused by disturbance of the boundary (magnetization transition region) between adjacent magnetization regions magnetized in opposite directions. Transient noise increases when the magnetostatic and exchange interactions between the magnetic particles are large or when the dispersion of the magnetic particle size is large.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a perpendicular magnetic recording medium and a magnetic storage device having an excellent S / N ratio and capable of increasing the recording density. That is.

According to an aspect of the present invention, there is provided a perpendicular magnetic recording medium including a substrate and a recording layer, wherein the recording layer is formed by sequentially laminating a first magnetic layer and a second magnetic layer from the substrate side. The first magnetic layer and the second magnetic layer each have an easy magnetization axis in a direction substantially perpendicular to the substrate surface, and a plurality of magnetic particles made of a ferromagnetic material and the magnetic particles are bonded to each other. The first magnetic layer and the second magnetic layer are made of a non-solid solution phase made of a separated nonmagnetic material, and the first magnetic layer and the second magnetic layer are perpendicular to the substrate surfaces of the first magnetic layer and the second magnetic layer, respectively. The gradients in the applied magnetic field strength equivalent to the coercive force of the magnetization curve when a magnetic field is applied along the magnetic field are α ₁ and α _2, and the anisotropic magnetic fields of the first magnetic layer and the second magnetic layer are When H _k1, H _k2, vertical, characterized in that it has a H _k1 <H _k2, and α ₁ <α ₂ relationship Magnetic recording medium.

According to the present invention, the first magnetic layer is set to be smaller than the second magnetic layer by setting the inclination α ₁ of the magnetization curve of the first magnetic layer to be smaller than the inclination α ₂ of the magnetization curve of the second magnetic layer. Since the medium noise has a low characteristic, the medium noise of the entire recording layer can be reduced.

Further, only the relationship of α ₁ <α ₂ can reduce the medium noise as described above, but the reproduction resolution tends to decrease, and the thermal stability of the magnetization recorded in the recording layer tends to decrease. Therefore, the relationship of H _k1 <H _k2 , that is, the anisotropic magnetic field H _k2 of the second magnetic layer is set larger than the anisotropic magnetic field H _k1 of the first magnetic layer. As a result, it is possible to provide both good reproduction resolution and excellent thermal stability of recorded magnetization while maintaining the preferable characteristics of low medium noise. That is, by setting the anisotropic magnetic field H _k2 of the second magnetic layer to be larger than the anisotropic magnetic field H _k1 of the first magnetic layer, the length of the magnetization transition region of the second magnetic layer itself is shortened. . Since each of the magnetic particles in the first magnetic layer is ferromagnetically coupled to the magnetic particle in the second magnetic layer, the first magnetic layer is parallel to the magnetization direction of each of the magnetic particles in the second magnetic layer. The magnetization direction of the magnetic particles in the layer is determined. Therefore, the magnetization transition region length of the first magnetic layer is approximately the same as the magnetization transition region length of the second magnetic layer. Therefore, the reproduction resolution is improved rather than lowered. Further, regarding the thermal stability of the recorded magnetization, from the relation of H _k1 <H _k2 , the thermal stability of the recorded magnetization of the second magnetic layer alone is the recorded magnetization of the first magnetic layer alone. Better than thermal stability. Since each magnetic particle of the first magnetic layer is ferromagnetically coupled to the magnetic particle of the second magnetic layer, the thermal stability of the recorded magnetization of the first magnetic layer is also improved, and the entire recording layer The thermal stability of the recorded magnetization is increased.

  Therefore, the perpendicular magnetic recording medium of the present invention has an excellent S / N ratio and has a good reproduction resolution at a high recording density and an excellent thermal stability of recorded magnetization. Therefore, a perpendicular magnetic recording medium capable of increasing the recording density can be realized.

  According to another aspect of the present invention, there is provided a magnetic storage device comprising recording / reproducing means having a magnetic head and any one of the perpendicular magnetic recording media.

  According to the present invention, a magnetic storage device having an excellent S / N ratio and capable of increasing the recording density can be realized.

  ADVANTAGE OF THE INVENTION According to this invention, the perpendicular magnetic recording medium which has the outstanding S / N ratio, its manufacturing method, and a magnetic storage apparatus can be provided.

  Embodiments will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic sectional view of a perpendicular magnetic recording medium of a first example according to the first embodiment of the present invention.

  Referring to FIG. 1, a perpendicular magnetic recording medium 10 of a first example includes a substrate 11, a soft magnetic backing layer 12, an orientation control layer 13, an underlayer 14, an intermediate layer 15, a recording layer 16 on the substrate 11. A protective film 20 and a lubricating layer 21 are sequentially laminated. In the perpendicular magnetic recording medium 10, the recording layer 16 is configured by laminating a first magnetic layer 18 and a second magnetic layer 19 in this order from the intermediate layer 15 side.

  The substrate 11 is composed of, for example, a plastic substrate, a crystallized glass substrate, a tempered glass substrate, a Si substrate, an aluminum alloy substrate, and the like. When the perpendicular magnetic recording medium 10 is in a tape shape, polyester (PET), polyethylene naphthalate ( PEN) and polyimide (PI) films having excellent heat resistance can be used.

  The soft magnetic backing layer 12 has, for example, a film thickness of 10 nm to 2 μm, and at least one selected from Fe, Co, Ni, Al, Si, Ta, Ti, Zr, Hf, V, Nb, C, and B It is made of an amorphous or microcrystalline soft magnetic material containing these elements. Examples of such soft magnetic materials include FeSi, FeAlSi, FeTaC, CoNbZr, CoZrTa, CoCrNb, NiFe, and NiFeNb. The soft magnetic backing layer 12 is not limited to one layer, and a plurality of layers may be laminated.

  The orientation control layer 13 is made of a metal material and may be in an amorphous state, a microcrystalline state, or a crystalline state. The metal material is particularly preferably a material having a face-centered cubic (bcc) structure in a crystalline state. Examples of such a metal material include Ta, W, Nb, Mo, and materials mainly composed of these metal elements. By using such a metal material, the crystal orientation of the underlying layer 14 is improved. That is, the underlayer 14 having a face-centered cubic (fcc) structure has a (111) crystal plane oriented parallel to the substrate surface, and the orientation is improved.

  The underlayer 14 is made of a crystalline metal material having an fcc structure. Since the fcc structure is a close-packed structure, the lattice matching is good when the intermediate layer 15 having a hexagonal close-packed (hcp) structure formed thereon is epitaxially grown. That is, the (001) plane of the intermediate layer 15 is aligned with the (111) crystal plane of the underlayer 14, and the intermediate layer 15 grows with good crystallinity.

  The metal material of the underlayer 14 is preferably a metal material mainly composed of Ni having an fcc structure, and more preferably a material containing Ni and Fe. Examples of such a material include NiFe and NiFeNb. The film thickness of the underlayer 14 is preferably set in the range of 3 nm to 10 nm.

  The intermediate layer 15 is made of a nonmagnetic metal material having an hcp structure. As such a metal material, Ru—X alloy (X = at least one element of Co, Cr, Fe, Ni, and Mn), CoCr, and CoCr alloy can be given as a main component of Ru and Ru. By using such a material, the lattice matching with the base layer 14 becomes good, and has good crystallinity, good orientation of the (001) crystal plane, and uniformity of crystal grains. Therefore, the crystallinity, crystal orientation and magnetic particle uniformity of the magnetic particles of the recording layer 16 formed thereon are improved.

  In addition, since the lattice constant of Ru or Ru-X alloy is close to the lattice constant of the alloy mainly composed of Co having the hcp structure used for the first magnetic layer 18, the lattice matching is good. . For this reason, the crystallinity of the initial growth portion of the magnetic particles of the first magnetic layer 18 in the vicinity of the interface with the intermediate layer 15 is improved, and the S / N ratio is hardly deteriorated even if the first magnetic layer 18 is thinned. Further, since the crystallinity of the magnetic particles of the first magnetic layer 18 is improved, the crystallinity of the magnetic particles of the second magnetic layer 19 thereon is improved.

  The thickness of the intermediate layer 15 is preferably set in the range of 5 nm to 20 nm. The thicker the intermediate layer 15 is, the better the crystallinity of the surface of the intermediate layer 15 is. However, when it exceeds 20 nm, so-called spacing loss increases, and the reproduction output tends to decrease.

  The recording layer 16 is formed by laminating a first magnetic layer 18 and a second magnetic layer 19 in this order on an intermediate layer 15. The first magnetic layer 18 and the second magnetic layer 19 are composed of magnetic particles having a columnar structure and a non-solid solution phase made of a nonmagnetic material that surrounds the magnetic particles and physically separates adjacent magnetic particles. That is, the first magnetic layer 18 and the second magnetic layer 19 have a so-called columnar granular structure. The magnetic particles extend in a direction substantially perpendicular to the substrate surface. Further, the non-solid solution phase is formed so as to be filled between each of a large number of magnetic particles. Such a columnar granular structure is formed in a self-organized manner by using a sputtering target made of a composite material of a ferromagnetic material and a nonmagnetic material by a sputtering method or the like. One magnetic particle is ideally composed of a single crystal region as a whole, but may have a plurality of single crystal regions, and may have crystal grain boundaries and crystal defects.

  The ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19 is made of a material selected from Co, CoCr, CoPt, CoCrTa, CoCrPt, and CoCrPt-M. Here, M is selected from B, Mo, Nb, Ta, W, Cu and alloys of these elements. By using such a ferromagnetic material, the magnetic particles have an easy axis of magnetization along a direction substantially perpendicular to the substrate surface. For example, when the ferromagnetic material has an hcp structure, the magnetic particles are crystal-oriented so that the c-axis is substantially perpendicular to the substrate surface.

The non-solid solution phase is composed of a non-magnetic material that does not form a solid solution with the above ferromagnetic material or does not form a compound. Such a nonmagnetic material includes at least one element selected from any one element selected from Si, Al, Ta, Zr, Y, Ti, and Mg, and O, N, and C. Consists of compounds with elements. Examples of such non-magnetic materials include oxides such as SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Y ₂ O ₃ , TiO ₂ , and MgO, Si ₃ N ₄ , AlN, and TaN. And nitrides such as ZrN, TiN and Mg ₃ N ₂ and carbides such as SiC, TaC, ZrC and TiC. Adjacent magnetic particles are physically separated from each other by such a non-solid solution phase made of a non-magnetic material. Therefore, the interaction between magnetic particles, for example, magnetostatic interaction and exchange interaction, is reduced, and medium noise can be reduced. The nonmagnetic material constituting the non-solid solution phase is preferably an insulating material. Thereby, the tunnel effect of the electrons responsible for ferromagnetism can be suppressed, and the exchange interaction between the magnetic particles can be reduced.

  Further, since the magnetic particles of the second magnetic layer 19 are each epitaxially grown on the surface of the magnetic particles of the first magnetic layer 18, the magnetic particles of the first magnetic layer 18 and the magnetic particles of the second magnetic layer 19 are different from each other. It is formed so as to substantially correspond to one to one. Therefore, the magnetic particles of the first magnetic layer 18 and the magnetic particles of the second magnetic layer 19 are ferromagnetically coupled to each other, and their magnetizations are parallel to each other.

  Each of the first magnetic layer 18 and the second magnetic layer 19 has a relationship of the following equations (1) and (2).

α ₁ <α ₂ (1)
H _k1 <H _k2 (2)
Here, α ₁ is the slope of the magnetization curve of the first magnetic layer 18, and α ₂ is the slope of the magnetization curve of the second magnetic layer 19. H _k1 is the anisotropic magnetic field of the first magnetic layer 18, and H _k2 is the anisotropic magnetic field of the second magnetic layer 19.

  The first magnetic layer 18 and the second magnetic layer 19 have the following functions and effects by having the relationship of the above formulas (1) and (2).

The inclinations α ₁ and α ₂ of the magnetization curves shown in the above equation (1) are obtained by applying a magnetic field in the direction perpendicular to the substrate surface and measuring the magnitude of the magnetization along the direction. Is the slope of the magnetization curve at a magnetic field strength that is substantially the same. The inclination α of the magnetization curve is obtained by differentiating the magnetization M at a magnetic field strength substantially equal to the coercive force with the magnetic field H, and is expressed as α = 4π × dM / dH in the CGS unit system. The inclination of the magnetization curve is related to the magnitude of the interaction between the magnetic particles in the magnetic layer. The smaller the inclination of the magnetization curve, the smaller the interaction, and the medium noise due to the magnetic layer tends to decrease. Therefore, by setting the relationship of the above equation (1), that is, the inclination α ₁ of the magnetization curve of the first magnetic layer 18 to be smaller than the inclination α ₂ of the magnetization curve of the second magnetic layer 19, the first magnetic layer 18. Has a characteristic that the medium noise is lower than that of the second magnetic layer 19. As a result, since a part of the recording layer 16 is composed of a layer with low medium noise, the medium noise of the entire recording layer 16 can be reduced.

  Furthermore, although the medium noise can be reduced as described above only by the relationship of the above equation (1), the magnetization transition region length increases and the reproduction resolution tends to decrease. The magnetization transition region is a region formed between a magnetization region formed by recording and a magnetization region formed adjacent thereto. The magnetization transition region is a region in which the magnetization direction changes. When the length of this region (magnetization transition region length) increases, the reproduction output at a high recording density decreases. That is, in such a case, the recording density dependency of the reproduction output is deteriorated, and the reproduction resolution is lowered.

  Furthermore, the thermal stability of the magnetization recorded in the recording layer 16 tends to decrease only by the relationship of the above formula (1). That is, since the interaction in the magnetic particles of the first magnetic layer 18 is reduced, the direction of microscopic magnetization is likely to be random due to heat, and the overall magnetization is likely to be reduced. That is, the thermal stability of magnetization decreases.

Therefore, the relationship of the above formula (2), that is, the anisotropic magnetic field of the second magnetic layer 19 is set larger than the anisotropic magnetic field of the first magnetic layer 18. As a result, it is possible to provide both good reproduction resolution and excellent thermal stability of recorded magnetization while maintaining the preferable characteristics of low medium noise. That is, by setting the anisotropic magnetic field H _k2 of the second magnetic layer 19 to be larger than the anisotropic magnetic field H _k1 of the first magnetic layer 18, the magnetization transition region length of the second magnetic layer 19 itself is shortened. . Since the magnetic particles of the first magnetic layer 18 are ferromagnetically coupled to the magnetic particles of the second magnetic layer 19 as described above, they are parallel to the magnetization directions of the magnetic particles of the second magnetic layer 19. The magnetization direction of the magnetic particles of the first magnetic layer 18 is determined. Therefore, the magnetization transition region length of the first magnetic layer 18 is approximately the same as the magnetization transition region length of the second magnetic layer 19. Therefore, the reproduction resolution is improved rather than lowered.

  Further, regarding the thermal stability of the recorded magnetization, since the anisotropic magnetic field of the second magnetic layer 19 is larger than the anisotropic magnetic field of the first magnetic layer 18 due to the relationship of the above equation (2), the second The thermal stability of the recorded magnetization of the magnetic layer 19 alone is superior to the thermal stability of the recorded magnetization of the first magnetic layer 18 alone. Since the magnetic particles of the first magnetic layer 18 are ferromagnetically coupled to the magnetic particles of the second magnetic layer 19, the thermal stability of the recorded magnetization of the first magnetic layer 18 is also improved, and the entire recording layer 16. The thermal stability of the recorded magnetization is increased.

  Further, since the second magnetic layer 19 is closer to the recording head (not shown) than the first magnetic layer 18, the applied magnetic field intensity is higher in the second magnetic layer 19. Therefore, by providing the second magnetic layer 19 having a larger anisotropic magnetic field on the recording head side, the reproduction resolution and the overwrite characteristic are improved as compared with the case where the first magnetic layer 18 and the second magnetic layer 19 are laminated in reverse. improves.

  Therefore, the perpendicular magnetic recording medium 10 can be provided with a good reproduction resolution and excellent thermal stability of recorded magnetization while maintaining a preferable characteristic of low medium noise.

Furthermore, it is preferable that the first magnetic layer 18 has an anisotropic magnetic field H _k1 set in a range of 8 kOe to 13 kOe in terms of low medium noise. Further, the first magnetic layer 18 is preferably set to have a magnetization curve slope α ₁ in the range of 1.0 to 2.0 in terms of low medium noise.

The second magnetic layer 19 preferably has an anisotropic magnetic field H _k2 set in the range of 10 kOe to 15 kOe in terms of high resolution, excellent writing performance, and excellent thermal stability of recorded magnetization. . Further, the second magnetic layer 19 is preferably set to have a magnetization curve slope α ₂ in a range of 1.5 to 3.0 in terms of excellent writing performance.

  Specifically, the relationship between the above formulas (1) and (2) is realized by using a material having the following composition relationship as the ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19. The

  For example, when a material containing CoCrPt is used as the ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19, the inclination α of the magnetization curve is lowered by increasing the Cr content. For example, by setting the Cr content of the first magnetic layer 18 to be higher than the Cr content of the second magnetic layer 19, the first magnetic layer 18 and the second magnetic layer 19 have the relationship of the above formula (1). It becomes like this.

  For example, when a material containing CoCrPt is used as the ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19, the anisotropic magnetic field can be increased by increasing the Pt content. For example, by setting the Pt content of the second magnetic layer 19 to be higher than the Pt content of the first magnetic layer 18, the first magnetic layer 18 and the second magnetic layer 19 have the relationship of the above formula (2). become.

  In addition, when the ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19 is made of a material containing CoCrPt, the anisotropic magnetic field is set so that the Pt content is substantially equal and the Co content is increased. Can be increased. That is, the Pt contents of the first magnetic layer 18 and the second magnetic layer 19 are set to be substantially equal, and the Co content of the second magnetic layer 19 is set to be larger than the Co content of the first magnetic layer 18. Thus, the first magnetic layer 18 and the second magnetic layer 19 have the relationship of the above formula (2). The anisotropic magnetic field can also be controlled by the content (molar fraction) of the nonmagnetic material in the first magnetic layer 18 and the second magnetic layer 19. By reducing the content of the nonmagnetic material, the anisotropic magnetic field can be increased.

  When the ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19 is made of CoCrPt or CoCrPt-M, for example, the Co content is 50 atomic% to 80 atomic%, and the Pt content is 12 atomic% to 30 atoms. %, M concentration is set to be more than 0 atomic% and 20 atomic% or less, and the rest is Cr content.

  In particular, the ferromagnetic material of the first magnetic layer 18 and the second magnetic layer 19 preferably has the following composition. The Pt content of the second magnetic layer 19 is set to 15 atomic% to 25 atomic%, and the Pt content of the first magnetic layer 18 is set to be smaller than that of the second magnetic layer 19. Then, the Cr content of the first magnetic layer 18 is set higher than that of the second magnetic layer 19. By setting in this way, the first magnetic layer 18 and the second magnetic layer 19 have the relationship of the above formulas (1) and (2), and are excellent in low medium noise, high reproduction resolution, and recorded magnetization. The thermal stability can be provided.

  The non-magnetic material of the non-solid solution phase of the first magnetic layer 18 and the second magnetic layer 19 is preferably set to have a molar fraction in the range of 4 mol% to 16 mol%, and 6 mol% to 16 mol%. More preferably, the range is set. If the molar fraction of the nonmagnetic material is less than 4 mol%, the magnetic particles are easily bonded to each other and the magnetic particles are not sufficiently separated from each other, so that the medium noise increases. On the other hand, when the molar fraction of the nonmagnetic material exceeds 16 mol%, the reproduction output is significantly reduced due to the decrease in saturation magnetization per unit volume, and the epitaxial growth is further inhibited.

  The film thicknesses of the first magnetic layer 18 and the second magnetic layer 19 are preferably set in the range of 3 nm to 20 nm, and more preferably set in the range of 6 nm to 12 nm.

  The second magnetic layer 19 is preferably smaller in thickness than the first magnetic layer 18. Since the second magnetic layer 19 has a larger anisotropic magnetic field than the first magnetic layer 18, the transition noise tends to increase. However, by reducing the thickness of the second magnetic layer 19, the transition noise is reduced. The medium noise can be further reduced.

  The protective film 20 has a thickness of 0.5 nm to 15 nm, for example, and is made of a material selected from amorphous carbon, hydrogenated carbon, carbon nitride, aluminum oxide, and the like. The material for the protective film 20 is not particularly limited.

  The lubrication layer 21 is made of, for example, a main chain lubricant made of perfluoropolyether having a film thickness of 0.5 nm to 5 nm. As the lubricant, for example, perfluoropolyether whose terminal group is made of —OH, piperonyl group or the like can be used. The lubricating layer 21 may or may not be provided depending on the material of the protective film 20.

  The perpendicular magnetic recording medium of the first example is excellent because the first magnetic layer 18 and the second magnetic layer 19 of the recording layer 16 have the relationship of the above formulas (1) and (2), so that the medium noise is low and excellent. It has an S / N ratio. In addition, the recording layer 16 has a good reproduction resolution at a high recording density and an excellent thermal stability of recorded magnetization. Therefore, a perpendicular magnetic recording medium capable of increasing the recording density can be realized.

  Next, a method for manufacturing a perpendicular magnetic recording medium according to the first embodiment will be described with reference to FIG.

  First, after cleaning and drying the surface of the substrate 11, the above-described soft magnetic backing layer 12 is formed on the substrate 11 by an electroless plating method, an electroplating method, a sputtering method, a vacuum evaporation method, or the like. Specifically, the film is formed by a DC magnetron method in an Ar gas atmosphere, for example, at a pressure of 0.5 Pa. It is preferable not to heat the substrate 11 during film formation.

  Next, the orientation control layer 13, the underlayer, and the intermediate layer 15 are sequentially formed on the soft magnetic backing layer 12 using a sputtering apparatus. Specifically, the film is formed by a DC magnetron method in an Ar gas atmosphere, for example, at a pressure of 0.5 Pa. It is preferable not to heat the substrate 11 during film formation.

  Next, the first magnetic layer 18 and the second magnetic layer 19 are formed on the intermediate layer 15 using a sputtering target made of the above-described ferromagnetic material and nonmagnetic material, using a sputtering apparatus. Specifically, using a sputtering target in which the above-described magnetic material and nonmagnetic material are combined by a DC or RF magnetron method, in an inert gas atmosphere, for example, a pressure of 2.00 Pa to 8.00 Pa (preferably 2.00 Pa). To 3.99 Pa), the first magnetic layer 18 and the second magnetic layer 19 are sequentially formed. When the first magnetic layer 18 and the second magnetic layer 19 are formed, oxygen may be added to the inert gas if the nonmagnetic material contains oxygen, and not when the nonmagnetic material contains nitrogen. Nitrogen may be added to the active gas.

  The first magnetic layer 18 and the second magnetic layer 19 may be formed by using a sputtering target made of a magnetic material and a sputtering target made of a nonmagnetic material and simultaneously sputtering these sputtering targets.

  Next, the protective film 20 is formed on the second magnetic layer 19 by using a sputtering method, a CVD method, an FCA (Filtered Cathodic Arc) method, or the like. In addition, when forming a protective film by CVD method, hydrocarbon gas, such as methane gas and ethylene gas, is used as material gas.

  Note that, from the step of forming the seed layer 12 to the step of forming the protective film 20, the cleanliness of the surface of the formed layer can be maintained by maintaining a vacuum or an inert gas atmosphere between the steps. This is preferable.

  Next, the lubricating layer 21 is formed on the surface of the protective film 20. The lubricating layer 21 is applied with a diluted solution obtained by diluting a lubricant with a solvent by using a dipping method, a spin coating method, or the like. Thus, the perpendicular magnetic recording medium of the first example is formed.

  Next, a perpendicular magnetic recording medium of a second example according to the first embodiment will be described. The perpendicular magnetic recording medium of the second example is a modification of the perpendicular magnetic recording medium of the first example.

  FIG. 2 is a schematic cross-sectional view of a perpendicular magnetic recording medium of a second example according to the first embodiment. In the figure, portions corresponding to the portions described above are denoted by the same reference numerals, and description thereof is omitted.

  Referring to FIG. 2, the perpendicular magnetic recording medium 30 of the second example includes a substrate 11, a soft magnetic backing layer 32, an orientation control layer 13, an underlayer 14, an intermediate layer 15, and a first magnetic layer on the substrate 11. The recording layer 16 composed of 18 and the second magnetic layer 19, the protective film 20, and the lubricating layer 21 are sequentially laminated. The perpendicular magnetic recording medium 30 is formed by laminating a soft magnetic backing layer 32 from the substrate 11 side in the order of a first soft magnetic layer 33, a nonmagnetic coupling layer 34, and a second soft magnetic layer 35. The perpendicular magnetic recording medium 30 is configured similarly to the perpendicular magnetic recording medium of the first example except that the soft magnetic backing layer 32 is different.

  The first soft magnetic layer 33 and the second soft magnetic layer 35 of the soft magnetic backing layer 32 are selected from the same material as that of the soft magnetic backing layer shown in FIG. The nonmagnetic coupling layer 34 is made of any of Ru, Rh, Ir, Ru-based alloy, Rh-based alloy, Ir-based alloy, and the like. The film thickness of the nonmagnetic coupling layer 34 is set in the range of 0.5 nm to 1.0 nm. By setting the nonmagnetic coupling layer 34 within this thickness range, the first soft magnetic layer 33 and the second soft magnetic layer 35 are antiferromagnetic with respect to each other via the nonmagnetic coupling layer 34. Exchange-coupled. Since the soft magnetic backing layer 32 has such a so-called laminated ferrimagnetic structure, the formation of magnetic domains in the first soft magnetic layer 33 and the second soft magnetic layer 35 is suppressed, and spike noise caused by domain wall movement can be suppressed. Although not shown, an adhesion film such as Cr or Ta may be provided between the substrate and the first soft magnetic layer 33.

  The perpendicular magnetic recording medium 30 of the second example has the same effect as that of the perpendicular magnetic recording medium of the first example. Further, the medium noise is further reduced by reducing spike noise, and the S / N ratio is excellent. .

  In the first and second perpendicular magnetic recording media 10 and 30 shown in FIGS. 1 and 2, it is preferable to provide the underlayer 14 as described above, but it may be omitted. Next, examples of the perpendicular magnetic recording medium according to the present embodiment will be described.

[Example 1]
The perpendicular magnetic recording medium of Example 1 has substantially the same configuration as the perpendicular magnetic recording medium of the second example shown in FIG. Specific configurations are shown below in order from the substrate side.

Substrate: Glass substrate Adhesion film: Cr film (5 nm)
First soft magnetic layer: CoNbZr film (30 nm)
Nonmagnetic coupling layer: Ru film (0.7 nm)
Second soft magnetic layer: CoNbZr film (30 nm)
Orientation control layer: Ta film (3 nm)
Underlayer: NiFe film (5 nm)
Intermediate layer: Ru film (15 nm)
First magnetic layer: (Co ₆₇ Cr ₁₈ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (8 nm)
Second magnetic layer: (Co ₇₀ Cr ₁₅ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (8 nm)
Protective film: Amorphous carbon film (4 nm)
Lubricating layer: perfluoropolyether (1 nm)
In addition, the numerical value in a parenthesis shows a film thickness. Further, the composition of the recording layer indicates the composition of the sputter target.

  The perpendicular magnetic recording medium (for measuring S / N ratio) of Example 1 was produced as follows. Using a cleaned glass substrate using a DC magnetron sputtering apparatus, in an argon gas atmosphere, the pressure is set to 0.5 Pa in the formation of the underlayer from the adhesion film, the intermediate layer, the first magnetic layer, and the first layer In forming the two magnetic layers, the film thickness was set to 4 Pa. At that time, the substrate was not heated. Next, the protective film was formed by supplying ethylene gas and argon gas with a plasma CVD apparatus, and the lubricating layer was formed by an immersion method.

  In addition, in order to measure the magnetic characteristics (anisotropy magnetic field and inclination of the magnetization curve) of each of the first magnetic layer and the second magnetic layer, a perpendicular magnetic recording medium having the following configuration was manufactured. Of the configuration of the perpendicular magnetic recording medium of Example 1 described above, the adhesive film to the second soft magnetic layer are omitted, and the first magnetic layer or the second magnetic layer is provided. The conditions for producing a perpendicular magnetic recording medium for measuring magnetic characteristics are the same as those for the perpendicular magnetic recording medium for measuring the S / N ratio. Also, perpendicular magnetic recording media for measuring magnetic properties having the same structure as described above were prepared for the perpendicular magnetic recording media of Examples 2 to 3 and Comparative Examples described below.

[Example 2]
The perpendicular magnetic recording medium of Example 2 has the same configuration as that of Example 1 except that the following first magnetic layer and second magnetic layer are different. The manufacturing method was the same as in Example 1.

First magnetic layer: (Co ₆₇ Cr ₁₈ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (11 nm)
Second magnetic layer: (Co ₇₇ Cr ₈ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (8 nm)
[Example 3]
The perpendicular magnetic recording medium of Example 3 has the same configuration as that of Example 1 except that the first magnetic layer and the second magnetic layer described below are different. The manufacturing method was the same as in Example 1.

First magnetic layer: (Co ₆₅ Cr ₂₀ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (11 nm)
Second magnetic layer: (Co ₇₅ Cr ₁₀ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (4 nm)
[Comparative example]
The perpendicular magnetic recording medium of the comparative example not according to the present invention has the same configuration as that of Example 1 except that one recording layer is used instead of the first magnetic layer and the second magnetic layer. The manufacturing method was the same as in Example 1.

Recording layer: (Co ₇₀ Cr ₁₅ Pt ₁₅ ) 90 mol%-(SiO ₂ ) 10 mol% film (16 nm)
FIG. 3 is a characteristic diagram of the perpendicular magnetic recording media of Examples and Comparative Examples.

  Referring to FIG. 3, in Examples 1 to 3, the inclination α of the magnetization curve is the relationship of the above formula (1), that is, the second magnetic layer is larger than the first magnetic layer. This is because in Examples 1 to 3, the Cr content is higher in the first magnetic layer than in the second magnetic layer.

  Further, the anisotropic magnetic field has the relationship of the above formula (2), that is, the second magnetic layer is larger than the first magnetic layer. In Examples 1 to 3, the Pt content is the same in the first magnetic layer and the second magnetic layer, and the Co content is higher in the second magnetic layer than in the first magnetic layer. Because it is.

  Regarding the S / N ratio, Examples 1 to 3 are larger than Comparative Examples in which the recording layer is composed of one layer, and the first magnetic layer and the second magnetic layer have the above formulas (1) and (2). It was confirmed that the S / N ratio was improved by having this relationship.

  Furthermore, in Examples 1 to 3, Example 2 and Example 3 have a larger S / N ratio than Example 1. This is because in Example 2 and Example 3, since the film thickness of the second magnetic layer was set smaller than the film thickness of the first magnetic layer, the medium noise was reduced.

  Moreover, when Example 2 and Example 3 are compared, Example 3 has a larger S / N ratio. This is because the anisotropic magnetic fields of the first magnetic layer and the second magnetic layer are lower in Example 3 than in Example 2. The decrease in the anisotropic magnetic field of Example 3 is due to the increase in Cr content of the first magnetic layer and the second magnetic layer of Example 3.

  The anisotropic magnetic field is measured by using a vibrating sample magnetometer (VSM) that can measure the amount of magnetization in two orthogonal directions using a perpendicular magnetic recording medium for measuring magnetic properties. The magnetization curve in the hard axis direction was measured. The substantially linear unsaturated portion of the obtained magnetization curve in the hard axis direction was linearly approximated to a straight line passing through the origin, and the absolute value of the magnetic field strength at which the magnetization is equivalent to the saturation magnetization in the straight line was defined as Hk. The anisotropic magnetic fields of the first magnetic layer and the second magnetic layer were measured separately.

  The inclination of the magnetization curve is measured by applying a magnetic field in a direction perpendicular to the substrate surface using a perpendicular magnetic recording medium for measuring magnetic characteristics, and detecting the amount of magnetization in the same direction as the magnetization curve. Got. Then, the inclination α of the magnetization curve in which the magnetic field intensity of the obtained magnetization curve is near the coercive force was obtained. The inclination α of the magnetization curve is expressed as α = 4π × dM / dH. α is a dimensionless quantity in the CGS unit system.

  The S / N ratio was measured by using a commercially available composite head composed of a spin stand, a single magnetic pole type recording element, and a GMR element, using a perpendicular magnetic recording medium for S / N ratio measurement. The average output V (mV) is measured by setting the linear recording density to 700 kFCI, and the medium noise Nm (mV) is integrated with the noise output in the band from 0.5 MHz to twice the recording frequency to obtain circuit noise and GMR. The measurement was performed under conditions excluding noise caused by the element, and the S / N ratio was 20 × log (V / Nm).

(Second Embodiment)
FIG. 4 is a plan view showing the main part of the magnetic memory device according to the second embodiment of the present invention. Referring to FIG. 4, the magnetic storage device 60 generally includes a housing 61. Within the housing 61, a hub 62 driven by a spindle (not shown), a perpendicular magnetic recording medium 63 fixed to the hub 62 and rotated, an actuator unit 64, and a radius of the perpendicular magnetic recording medium 63 attached to the actuator unit 64 An arm 65 and a suspension 66 that move in the direction, and a magnetic head 68 supported by the suspension 66 are provided.

  The magnetic head 68 is composed of, for example, a reproducing head including a single magnetic pole type recording head and a GMR (Giant Magneto Resistive) element.

  The single-pole type recording head has a main magnetic pole made of a soft magnetic material for applying a recording magnetic field to the perpendicular magnetic recording medium 63, a return yoke magnetically connected to the main magnetic pole, and recording on the main magnetic pole and the return yoke. It is composed of a recording coil for inducing a magnetic field. The single-pole type recording head applies a recording magnetic field from the main magnetic pole in the perpendicular direction to the perpendicular magnetic recording medium 63 to form perpendicular magnetization in the recording layer of the perpendicular magnetic recording medium 63.

  The reproducing head also includes a GMR element, and the GMR element senses the direction of the magnetic field in which the magnetization of the perpendicular magnetic recording medium 63 leaks as a resistance change, and obtains information recorded on the recording layer of the perpendicular magnetic recording medium 63. Can do. Note that a TMR (Ferromagnetic Tunnel Junction Magneto Resistive) element or the like can be used instead of the GMR element.

  The perpendicular magnetic recording medium 63 is the perpendicular magnetic recording medium of the first example or the second example according to the first embodiment. The perpendicular magnetic recording medium 63 has an excellent S / N ratio and has a good reproduction resolution at a high recording density and an excellent thermal stability of recorded magnetization, so that a magnetic storage capable of increasing the recording density is possible. The device 60 is realized.

  The basic configuration of the magnetic storage device 60 according to the present embodiment is not limited to that shown in FIG. 4, and the magnetic head 68 is not limited to the configuration described above, and a known magnetic head is used. it can. Further, the perpendicular magnetic recording medium 63 used in the present invention is not limited to a magnetic disk but may be a magnetic tape.

  According to the present embodiment, since the magnetic storage device 60 has both a good reproduction resolution at a high recording density and an excellent thermal stability of recorded magnetization, a high recording density can be achieved.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the present invention described in the claims. It can be changed.

In addition, the following additional notes are disclosed regarding the above description.
(Appendix 1) A perpendicular magnetic recording medium comprising a substrate and a recording layer,
The recording layer is formed by sequentially laminating a first magnetic layer and a second magnetic layer from the substrate side,
Each of the first magnetic layer and the second magnetic layer has an easy magnetization axis in a direction substantially perpendicular to the substrate surface, and separates the magnetic particles from a plurality of magnetic particles made of a ferromagnetic material. It consists of a non-solid solution phase made of nonmagnetic material
The inclinations of the applied magnetic field strength equivalent to the coercive force of the magnetization curve when a magnetic field is applied along the direction perpendicular to the substrate surfaces of the first magnetic layer and the second magnetic layer are α ₁ and α _2. And the anisotropic magnetic fields of the first magnetic layer and the second magnetic layer are H _k1 and H _k2 , respectively.
The perpendicular magnetic recording medium, wherein the first magnetic layer and the second magnetic layer have a relationship of α ₁ <α ₂ and H _k1 <H _k2 .
(Supplementary Note 2) The first magnetic layer and the second magnetic layer may be any one of the group consisting of a Co-based alloy in which the ferromagnetic material includes CoCr, CoPt, CoCrTa, CoCrPt, and CoCrPt-M. The perpendicular magnetic recording medium according to appendix 1, wherein the perpendicular magnetic recording medium is made of a material, and the M is made of at least one material selected from the group consisting of B, Mo, Nb, Ta, W, Cu, and alloys thereof.
(Supplementary Note 3) The ferromagnetic material is made of CoCrPt or CoCrPt-M, and the M is made of at least one material selected from the group consisting of B, Mo, Nb, Ta, W, Cu, and alloys thereof.
The perpendicular magnetic recording medium according to claim 1, wherein the second magnetic layer has a higher Pt content and a lower Cr content than the first magnetic layer.
(Appendix 4) A perpendicular magnetic recording medium comprising a substrate and a recording layer,
The recording layer is formed by sequentially laminating a first magnetic layer and a second magnetic layer from the substrate side,
The first magnetic layer and the second magnetic layer are:
Each having an easy magnetization axis in a direction substantially perpendicular to the substrate surface, comprising a plurality of magnetic particles made of a ferromagnetic material and a non-solid solution phase made of a non-magnetic material that separates the magnetic particles from each other,
The ferromagnetic material is made of CoCrPt or CoCrPt-M, and the M is made of at least one material selected from the group consisting of B, Mo, Nb, Ta, W, Cu and alloys thereof;
The perpendicular magnetic recording medium, wherein the second magnetic layer has a higher Pt content and a lower Cr content than the first magnetic layer.
(Appendix 5) A perpendicular magnetic recording medium comprising a substrate and a recording layer,
The recording layer is formed by sequentially laminating a first magnetic layer and a second magnetic layer from the substrate side,
Each of the first magnetic layer and the second magnetic layer has an easy magnetization axis in a direction substantially perpendicular to the substrate surface, and separates the magnetic particles from a plurality of magnetic particles made of a ferromagnetic material. It consists of a non-solid solution phase made of a non-magnetic material,
The ferromagnetic material is made of CoCrPt or CoCrPt-M, and the M is made of at least one material selected from the group consisting of B, Mo, Nb, Ta, W, Cu and alloys thereof;
The first magnetic layer and the second magnetic layer have substantially the same Pt content,
The perpendicular magnetic recording medium, wherein the second magnetic layer has a higher Co content and a lower Cr content than the first magnetic layer.
(Supplementary note 6) The perpendicular magnetic recording medium according to any one of supplementary notes 1 to 5, wherein the second magnetic layer has a thickness smaller than that of the first magnetic layer.
(Supplementary note 7) The nonmagnetic material is at least any one of a group consisting of Si, Al, Ta, Zr, Y, and Mg, and a group consisting of O, C, and N The perpendicular magnetic recording medium according to any one of appendices 1 to 6, wherein the perpendicular magnetic recording medium is a compound with a seed element.
(Appendix 8) A soft magnetic backing layer is further provided between the substrate and the recording layer,
The soft magnetic backing layer has two soft magnetic layers and a nonmagnetic coupling layer sandwiched between the two soft magnetic layers, and the two soft magnetic layers are antiferromagnetically exchange-coupled. The perpendicular magnetic recording medium according to any one of appendices 1 to 7.
(Appendix 9) Recording / reproducing means having a magnetic head;
A magnetic storage device comprising: the perpendicular magnetic recording medium according to any one of appendices 1 to 7.

1 is a schematic cross-sectional view of a first example perpendicular magnetic recording medium according to a first embodiment of the invention. It is a schematic sectional drawing of the perpendicular magnetic recording medium of the 2nd example which concerns on 1st Embodiment. It is a characteristic view of the perpendicular magnetic recording medium of an Example and a comparative example. It is a top view which shows the principal part of the magnetic memory device based on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 63 Perpendicular magnetic recording medium 11 Substrate 12, 32 Soft magnetic backing layer 13 Orientation control layer 14 Underlayer 15 Intermediate layer 16 Recording layer 18 First magnetic layer 19 Second magnetic layer 20 Protective film 21 Lubricating layer 33 First soft magnetic Layer 34 Nonmagnetic coupling layer 35 Second soft magnetic layer 60 Magnetic storage device

Claims (5)

A perpendicular magnetic recording medium comprising a substrate and a recording layer,
The recording layer is formed by sequentially laminating a first magnetic layer and a second magnetic layer from the substrate side,
Each of the first magnetic layer and the second magnetic layer has an easy magnetization axis in a direction substantially perpendicular to the substrate surface, and separates the magnetic particles from a plurality of magnetic particles made of a ferromagnetic material. It consists of a non-solid solution phase made of a non-magnetic material,
The inclinations of the applied magnetic field strength equivalent to the coercive force of the magnetization curve when a magnetic field is applied along the direction perpendicular to the substrate surfaces of the first magnetic layer and the second magnetic layer are α ₁ and α _2. And the anisotropic magnetic fields of the first magnetic layer and the second magnetic layer are H _k1 and H _k2 , respectively.
The perpendicular magnetic recording medium, wherein the first magnetic layer and the second magnetic layer have a relationship of α ₁ <α ₂ and H _k1 <H _k2 . The ferromagnetic material is made of CoCrPt or CoCrPt-M, and the M is made of at least one material selected from the group consisting of B, Mo, Nb, Ta, W, Cu and alloys thereof.
2. The perpendicular magnetic recording medium according to claim 1, wherein the second magnetic layer has a higher Pt content and a lower Cr content than the first magnetic layer. A perpendicular magnetic recording medium comprising a substrate and a recording layer,
The recording layer is formed by sequentially laminating a first magnetic layer and a second magnetic layer from the substrate side,
Each of the first magnetic layer and the second magnetic layer has an easy magnetization axis in a direction substantially perpendicular to the substrate surface, and separates the magnetic particles from a plurality of magnetic particles made of a ferromagnetic material. It consists of a non-solid solution phase made of a non-magnetic material,
The ferromagnetic material is made of CoCrPt or CoCrPt-M, and the M is made of at least one material selected from the group consisting of B, Mo, Nb, Ta, W, Cu and alloys thereof;
The first magnetic layer and the second magnetic layer have substantially the same Pt content,
The perpendicular magnetic recording medium, wherein the second magnetic layer has a higher Co content and a lower Cr content than the first magnetic layer.   The perpendicular magnetic recording medium according to claim 1, wherein the second magnetic layer has a smaller film thickness than the first magnetic layer. Recording / reproducing means having a magnetic head;
A magnetic storage device comprising: the perpendicular magnetic recording medium according to claim 1.

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