JP2005251373A - Magnetic recording medium, manufacturing method of the same, and magnetic storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium which has improved resolution, excellent recording performance such as overwrite characteristic, and an excellent and high S/N ratio and thermal stability, and to provide a manufacturing method of the magnetic recording medium and a magnetic storage device thereof. <P>SOLUTION: The magnetic recording medium 10 is obtained by forming a first seed layer 12, a second seed layer 13, a first underlayer 14, a second underlayer 15, a first magnetic layer 16, a nonmagnetic binding layer 18, a second magnetic layer 19, a protective layer 20 and a lubricant layer 21 in order on a substrate 11. The first underlayer 14 is deposited by using Cr or a Cr-based alloy having a bcc crystal structure in an atmosphere added with nitrogen gas of 0.01 to 0.5% by volume by sputter technique. The second underlayer 15 is deposited in an atmosphere containing no nitride or an atmosphere added with nitrogen gas of ≤0.10% by volume by using material similar to that of the first underlayer 14. A coercive force squareness ratio is increased to properly lower an exchange coupling magnetic field. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic recording medium suitable for high-density recording, a manufacturing method thereof, and a magnetic storage device, and more particularly, a magnetic recording medium having a recording layer in which two magnetic layers are antiferromagnetically exchange-coupled, and a manufacturing method thereof And a magnetic storage device.

In recent years, high-density recording has been promoted rapidly, showing an annual growth rate of 100%. In the mainstream in-plane recording method, the limit of the surface recording density is expected to be 100 to 200 Gb / in ² . The reason is that in the high-density recording area, medium noise increases, output decreases, and S / N ratio decreases. Further, in the in-plane recording method, when the recording density is high, the self-demagnetizing field and the demagnetizing field from the adjacent bits increase with respect to the written bits, so that thermal stability becomes a problem.

  In order to reduce medium noise, it is necessary to reduce the size of magnetic particles, which are crystal grains constituting the recording layer, and to reduce the magnetic interaction between the magnetic particles. The refinement of the magnetic particles can promote the reduction of the zigzag of the boundary between the magnetization units, that is, the magnetization transition region, and reduce the medium noise. As a miniaturization technique, a technique of adding Ta, Nb, B, P or the like to a CoCr alloy constituting the recording layer is known. In addition, there is known a technique for refining the magnetic grains epitaxially grown thereon by refining the crystal grain size of the underlayer which is the base of the recording layer. Proposals have been made to reduce the thickness of the base layer and to add B to the base layer (for example, see Non-Patent Document 1).

  Further, as a technique for reducing the magnetic interaction between the magnetic particles, the Cr content of the CoCr alloy in the recording layer and the B content as an additive element are increased to promote segregation, and due to the grain boundaries between the formed magnetic particles. It is known that isolating magnetic particles is effective.

On the other hand, in the in-plane magnetic recording medium, the solitary wave half width PW50 of the reproduced output waveform is expressed by the following formula (1) between the coercive force Hc, the residual magnetization Mr, and the film thickness t of the recording layer. ) Is known to have a relationship.
PW50 = (2 (a + d) ² + (a / 2) ² ) ^1/2 (1)
Where a∝ (t × Mr / Hc) ^1/2 and d is the magnetic spacing. From equation (1), it can be seen that in order to reduce the solitary wave half width PW50, the coercive force Hc is increased and the film thickness t is reduced. Therefore, the smaller the solitary wave half width PW50 is, the higher the resolution of the reproduced signal is. Therefore, in order to increase the recording density, it is desirable to reduce the thickness of the recording layer and increase the coercive force.

  However, if the miniaturization of magnetic particles and the reduction of magnetic interaction are promoted, the demagnetizing field increases as the recording density increases, and the problem of thermal stability becomes more serious. As a countermeasure, a method of increasing the anisotropy magnetic field Hk of the recording layer has been taken. However, when the anisotropy magnetic field Hk is increased, recording becomes difficult, and the recording magnetic field increases, that is, the high saturation magnetic flux density of the recording head element. Development of magnetic pole materials is essential. The development of magnetic pole materials has to satisfy not only high saturation magnetic flux density but also various required characteristics, which is very difficult.

A magnetic recording medium (so-called synthetic ferrimagnetic medium (SFM)) including two magnetic layers that are antiferromagnetically exchange-coupled as recording layers as a magnetic recording medium that achieves both reduction of medium noise and thermal stability. It has been proposed (see, for example, Patent Document 1). In synthetic ferrimagnetic media, the volume of the magnetic particles becomes the sum of the volume of the magnetic particles of the two magnetic layers that are antiferromagnetically exchange-coupled, and the thermal stability is significantly improved. Thus, it is possible to achieve low medium noise and high S / N ratio as well as thermal stability.
JP 2001-056924 A M. Yu et al., IEEE Trans. Magn., Vol. 39 (1997) p. 2261

  However, in the synthetic ferrimagnetic medium, if the magnetic layer thinning method described above is employed in order to improve the resolution, the coercive force squareness ratio is lowered, and conversely, the resolution is lowered. Further, there arises a problem that the Siso / Nm ratio between the solitary wave average signal output Siso and the medium noise Nm, and the S / Nm ratio between the average output S and the medium noise Nm at the maximum used recording density are deteriorated.

  In addition, if the exchange coupling energy acting between the two magnetic layers is excessively large, the thermal stability is improved, but the recording performance such as overwrite characteristics and NLTS (non-linear transition shift) characteristics deteriorates. Occurs. There is a method to solve the problem by increasing the recording magnetic field, but as described above, it is difficult to increase the recording magnetic field.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to improve the resolution and to have excellent recording performance such as overwrite characteristics, and to have an excellent high S / N ratio and thermal stability. Magnetic recording medium, method of manufacturing the same, and magnetic storage device

  According to one aspect of the present invention, a substrate, an underlayer formed on the substrate, a first magnetic layer formed on the underlayer, and a non-layer formed on the first magnetic layer A magnetic coupling layer and a second magnetic layer formed on the non-magnetic coupling layer, wherein the first magnetic layer and the second magnetic layer are exchange-coupled and no external magnetic field is applied. A magnetic recording medium in which the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other, wherein the underlayer is Cr or a Cr-based alloy having a bcc crystal structure and contains nitrogen A magnetic recording medium is provided.

  According to the present invention, the recording layer is formed by sequentially laminating the first magnetic layer, the nonmagnetic coupling layer, and the second magnetic layer, and the magnetization of the first magnetic layer and the second magnetic layer are applied without applying an external magnetic field. Therefore, the magnetic recording medium of the present invention has excellent thermal stability. Furthermore, according to the present invention, by providing a base layer made of Cr containing Cr or a Cr-based alloy, the coercive force squareness ratio of the magnetic recording medium can be increased, and the resolution and S / N ratio can be improved. Therefore, a magnetic recording medium having an excellent S / N ratio and thermal stability can be realized.

  The underlayer may be formed in an atmosphere gas containing nitrogen gas of 0.01 volume% or more and 0.50 volume% or less.

  Between the underlayer and the first magnetic layer, Cr or a Cr-based alloy having a bcc crystal structure, or another underlayer containing the Cr or Cr-based alloy and containing nitrogen may be formed. . The other underlayer may be formed in an atmospheric gas containing a nitrogen gas containing 0.00% by volume or more and 0.10% by volume or less of Cr or Cr-based alloy having a bcc crystal structure. By providing such other underlayer, the coercive force squareness ratio is greatly increased, and the overwrite characteristics and the S / N ratio are greatly improved. Furthermore, you may comprise another base layer from the material which does not contain nitrogen substantially. In the specification and claims of the present application, the “material substantially free of nitrogen” refers to a material of a film formed in an atmosphere gas to which nitrogen is not added using a material that does not contain nitrogen.

  According to another aspect of the present invention, the substrate, the underlayer formed on the substrate, the first magnetic layer formed on the underlayer, and the first magnetic layer are formed. A nonmagnetic coupling layer and a second magnetic layer formed on the nonmagnetic coupling layer, wherein the first magnetic layer and the second magnetic layer are exchange-coupled and no external magnetic field is applied. A method of manufacturing a magnetic recording medium in which the magnetization of a first magnetic layer and the magnetization of a second magnetic layer are antiparallel to each other, comprising the step of forming the underlayer on the substrate, and forming the underlayer In the process, a method of manufacturing a magnetic recording medium is provided, in which Cr or a Cr-based alloy having a bcc crystal structure is formed in an atmosphere gas containing nitrogen gas.

  According to the present invention, an underlayer of a magnetic recording medium having a recording layer in which a first magnetic layer and a second magnetic layer stacked with a nonmagnetic coupling layer interposed therebetween are antiferromagnetically exchange-coupled, has a bcc crystal structure. By depositing Cr or Cr-based alloy in an atmosphere gas containing nitrogen gas, the coercive force squareness ratio of the magnetic recording medium can be increased, and the resolution and overwrite characteristics can be improved. As a result, a magnetic recording medium having excellent thermal stability and S / N ratio can be realized. Here, by forming the underlayer in an atmospheric gas containing nitrogen gas, the exchange coupling magnetic field between the first magnetic layer and the second magnetic layer is reduced, and the recording magnetic field in which each magnetization is applied from the magnetic head. It becomes easy to switch with respect to switching, and overwrite characteristics are improved. Here, the bcc structure means a body-centered cubic structure.

  The method further includes the step of forming another underlayer between the underlayer and the first magnetic layer, and the other underlayer forming step includes 0.10% by volume or less of Cr or Cr-based alloy having a bcc crystal structure. The film may be formed in an atmospheric gas containing a nitrogen gas. By depositing another underlayer between the underlayer and the first magnetic layer in an atmospheric gas containing 0.10 volume% or less of nitrogen gas using Cr or a Cr-based alloy having a bcc crystal structure, An excellent S / N ratio can be realized by increasing the coercivity squareness ratio and the like.

  In particular, the base layer is formed in an atmosphere gas containing 0.01% to 0.50% by volume of nitrogen gas, and the other base layer is formed of at least one of the group of He, Ne, Ar, Kr, and Xe. By forming the film in a rare gas atmosphere containing one kind, the coercive force squareness ratio can be remarkably increased, and the resolution, overwrite characteristics, and S / N ratio can be improved. By adding nitrogen gas, an underlayer having a good crystal grain size and crystal grain size distribution is formed, and by forming another underlayer on the underlayer in a rare gas atmosphere, the underlayer is inherited. The coercive force squareness ratio and the like can be increased and improved by the good crystal grain size and crystal grain size distribution and the good crystallinity of the other underlayer itself.

  The Cr-based alloy having a bcc crystal structure is an alloy composed of Cr and at least one additive element selected from the group consisting of Mo, W, V, and Ti, and the underlayer and the other underlayer are the same. It is good also as a structure which contains the said additive element and the additive element density | concentration in atomic percent is higher in the other base layer than the said base layer. By sequentially increasing the lattice spacing from the underlayer to another underlayer by the additive element, and improving the lattice matching with the Co-based alloy such as CoCrPt of the first magnetic layer and the second magnetic layer, the first magnetic layer and the second magnetic layer In-plane orientation and crystallinity of the magnetic layer can be improved.

  According to another aspect of the present invention, there is provided a magnetic storage device comprising any one of the above magnetic recording media or a magnetic recording medium formed by any one of the above manufacturing methods, and a recording / reproducing unit.

  According to the present invention, the magnetic recording medium has excellent coercivity squareness ratio, resolution, and overwrite characteristics, and also has excellent thermal stability and S / N ratio, and thus excellent thermal stability. And a magnetic storage device having an S / N ratio can be realized.

  According to the present invention, an underlayer of a magnetic recording medium having a recording layer in which a first magnetic layer and a second magnetic layer stacked with a nonmagnetic coupling layer interposed therebetween are antiferromagnetically exchange-coupled, has a bcc crystal structure. By depositing Cr or Cr-based alloy in an atmospheric gas containing nitrogen gas, the coercive force squareness ratio of the magnetic recording medium can be increased, and the resolution and overwrite characteristics can be improved. As a result, a magnetic recording medium and a magnetic storage device having an excellent S / N ratio and thermal stability can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a magnetic recording medium manufactured by the manufacturing method according to the present invention. Referring to FIG. 1, a magnetic recording medium 10 includes a substrate 11, a first seed layer 12, a second seed layer 13, a first underlayer 14, a second underlayer 15, and a first magnetic layer on the substrate 11. The layer 16, the nonmagnetic coupling layer 18, the second magnetic layer 19, the protective layer 20, and the lubricating layer 21 are sequentially stacked. The magnetic recording medium 10 has an exchange coupling structure in which the first magnetic layer 16 and the second magnetic layer 19 are antiferromagnetically exchange coupled via the nonmagnetic coupling layer 18, and no external magnetic field is applied. In this state, the residual magnetizations of the first magnetic layer 16 and the second magnetic layer 19 are in antiparallel directions. Hereinafter, a specific configuration and manufacturing method of the magnetic recording medium 10 will be described.

  As the substrate 11, for example, a disk-shaped plastic substrate, a glass substrate, a NiP-plated aluminum alloy substrate, a silicon substrate, or the like can be used. In particular, when the substrate 11 is in a tape shape, a plastic film such as PET, PEN, or polyimide is used. Can be used. The substrate 11 may or may not be textured. The texture processing is formed in the circumferential direction, that is, the track direction when the magnetic recording medium 10 is a magnetic disk.

  Before the first seed layer 12 is formed, the substrate 11 is heated to, for example, 180 ° C. in a vacuum or a rare gas atmosphere. Organic substances and moisture adhering to the surface of the substrate 11 can be removed, and crystal growth of each layer from the first seed layer 12 to the second magnetic layer 19 formed on the substrate 11 can be promoted. Moreover, when forming each layer from the 1st seed layer 12 to the 2nd magnetic layer 19, you may heat the board | substrate 11 in a vacuum as needed. Crystal growth can be promoted and Cr segregation in the first magnetic layer 16 and the second magnetic layer 19 can be promoted.

  Hereinafter, in the film formation process from the first seed layer 12 to the second magnetic layer 19, the film formation is performed in a rare gas atmosphere with the pressure set at, for example, 0.67 Pa unless otherwise specified.

  The first seed layer 12 is made of a non-magnetic amorphous metal such as NiP, CoW, AlTi, CrTi, etc. using a sputtering method, a vacuum evaporation method, a plating method, or the like, and the surface is textured. Well, it may not be given. When the first seed layer 12 is NiP, CoW or the like, the surface is preferably oxidized. The in-plane orientation of the c-axis of the first magnetic layer 16 and the second magnetic layer 19 is improved. A known material that improves the c-axis orientation can be used instead of NiP.

  The second seed layer 13 is made of an amorphous metal such as NiP, CoW, or CrTi, or an alloy having a B2 structure such as AlRu, NiAl, or FeAl, using a sputtering method or a vacuum deposition method.

  When the second seed layer 13 is an amorphous metal, it may contain oxygen or nitrogen. The second seed layer 13 is obtained by forming a film using such an amorphous metal material in an atmosphere containing oxygen gas or nitrogen gas. The second seed layer 13 may contain oxygen or nitrogen only near the surface thereof. The second seed layer 13 is formed by depositing an amorphous metal material in a rare gas atmosphere, and then oxidizing or nitriding the surface. By doing so, the orientation of the (200) plane or the (112) plane of the first underlayer 14 can be improved.

  The second seed layer 13 may or may not be textured. The texture processing described above is formed in the circumferential direction, that is, the track direction when the magnetic recording medium 10 is a magnetic disk. Further, one of the first seed layer 12 and the second seed layer 13 may be omitted.

  The first underlayer 14 is made of Cr or a Cr-based alloy having a bcc crystal structure and nitrogen. The first underlayer 14 is formed using Cr or a Cr-based alloy having a bcc crystal structure by sputtering in a rare gas atmosphere containing nitrogen gas. The film thickness of the first underlayer 14 is set in the range of 0.5 nm to 10 nm, and is preferably set in the range of 0.5 nm to 6.0 nm from the viewpoint of the S / N ratio. In addition, when the 2nd base layer 15 contains nitrogen, the 1st base layer 14 does not need to contain nitrogen. The first underlayer 14 can be obtained by depositing Cr or a Cr-based alloy in an atmosphere in which no nitrogen gas is added.

  The Cr-based alloy having the bcc crystal structure constituting the first underlayer 14 includes, for example, Mo, W, V, and Ti as elements added to Cr, and may contain two or more of these elements. These elements have the effect of widening the lattice spacing of Cr, and can improve the lattice matching with the first magnetic layer 16 and the second magnetic layer 19.

  The addition amount of Mo, W, and V in the Cr-based alloy is selected from the range of more than 0 atomic% and less than 100 atomic%, and is appropriately selected according to the lattice constants of the first magnetic layer 16 and the second magnetic layer 19 described later. Selected. For example, when the first magnetic layer 16 is made of a CoCr alloy and the second magnetic layer 19 is a CoCrPtB alloy, the amount of Mo added in CrMo is 20 atomic% to 35 atomic% in terms of lattice matching in the in-plane direction. In CrW, the addition amount of W is preferably 15 to 30 atomic percent, and in CrV, the addition amount of V is preferably 15 to 30 atomic percent. In particular, when the first magnetic layer 16 is made of a CoCr alloy and the second magnetic layer 19 is a CoCrPtB alloy containing about 11 atomic% Pt, the lattice matching in the in-plane direction is improved in the composition range of CrMo, CrW, and CrV. To do.

  Further, the addition amount of Ti in the CrTi alloy is preferably selected from the range of more than 0 atomic% and not more than 30 atomic%. If it exceeds 30 atomic%, the CrTi alloy tends to be microcrystallized or amorphous, and the crystal orientation of the first magnetic layer 16 and the second magnetic layer 19 deteriorates.

  The Cr-based alloy may be, for example, CrTa or CrMn having a bcc crystal structure and an in-plane crystal orientation of (200) in addition to the above-described alloys. When the first magnetic layer 16 and the second magnetic layer 19 are made of a Co-based alloy, the in-plane crystal orientation can be (110), and good c-axis orientation can be obtained.

  Further, B may be added to the above Cr or Cr-based alloy. The crystal grain size of the first underlayer 14 can be reduced, and the crystal grain size of the first magnetic layer 16 and the second magnetic layer 19 can be reduced. The addition amount of B is preferably more than 0 atomic% and not more than 10 atomic%. If the amount of B added exceeds 10 atomic%, the crystal orientation of the first magnetic layer 16 and the second magnetic layer 19 deteriorates.

  Further, the nitrogen gas added to the rare gas when forming the first underlayer 14 increases the coercive force squareness ratio, as will be apparent from examples described later, and the resolution, overwrite characteristics, S / N ratio is improved. The amount of nitrogen gas added to the rare gas is preferably selected from the range of 0.01% by volume to 0.50% by volume, more preferably 0.05% by volume to 0.50% by volume. In particular, the coercive force squareness ratio is greatly increased, and the overwrite characteristics and the S / N ratio are greatly improved. When the amount of nitrogen gas added exceeds 0.50% by volume, the coercive force is significantly lowered with respect to the amount of nitrogen gas added, so 0.50% by volume or less is preferable from the viewpoint of production stability. The rare gas is selected from at least one of the group of He, Ne, Ar, Kr, and Xe.

  Furthermore, the first underlayer 14 may be composed of a plurality of layers. In this case, it is preferable to set the total thickness of the plurality of layers to the same thickness as that of one layer. The enlargement of crystal grains constituting the first underlayer 14 can be suppressed, and the enlargement of crystal grains of the first magnetic layer 16 and the second magnetic layer 19 can be suppressed.

  The second underlayer 15 is made of Cr or a Cr-based alloy having a bcc crystal structure, or Cr or a Cr-based alloy having a bcc crystal structure and nitrogen. Furthermore, the second underlayer 15 preferably has a lower nitrogen concentration than the first underlayer. The second underlayer 15 is formed using Cr or a Cr-based alloy having a bcc crystal structure by a sputtering method in a rare gas atmosphere or a rare gas atmosphere containing nitrogen gas. The film thickness of the second underlayer 15 is set in the range of 0.5 nm to 5 nm, for example. For the Cr-based alloy having the bcc crystal structure constituting the second underlayer 15, the same material as that of the first underlayer 14 can be used.

  Furthermore, the same Cr-based alloy (when the additive elements are Mo, W, V, and Ti) are the same as the material constituting the first underlayer 14 as the material constituting the second underlayer 15. It is preferable that the second underlayer 15 has a larger amount of added element to Cr. By gradually expanding the lattice spacing in the in-plane direction from the first underlayer 14 to the second underlayer 15 by the additive element, the first magnetic layer 16 and the second magnetic layer 19 can be formed without causing excessive lattice distortion. Lattice matching can be enhanced, the in-plane orientation and crystallinity of the first magnetic layer 16 and the second magnetic layer 19 can be improved, and as a result, the S / N ratio can be improved. For the same reason, when the first underlayer 14 is made of Cr, the second underlayer 15 is preferably made of a Cr-based alloy.

  As the atmospheric gas for forming the second underlayer 15, a rare gas or a rare gas added with a nitrogen gas is used. The rare gas is the above-described rare gas, and when nitrogen gas is added, it is selected from a range of 0.10% by volume or less. The coercive force squareness ratio and the S / N ratio can be improved. If it exceeds 0.10% by volume, the average output decreases more rapidly than when nitrogen gas is not added. It is presumed that the in-plane orientation of the first magnetic layer 16 formed on the second underlayer 15 deteriorates, and the in-plane orientation is inherited by the second magnetic layer 19 and the average output is reduced. .

  For these reasons, when forming the second underlayer 15, it is particularly preferable to use a rare gas to which no nitrogen gas is added, that is, an atmosphere gas containing only a rare gas. The coercive force squareness ratio and the S / N ratio are improved as compared with the case where nitrogen gas is added, and the average output can be maintained. This is because when the nitrogen gas is not added to the second underlayer 15, the surface activity of the second underlayer 15 is higher and the first magnetic layer 16 is deposited with good crystallinity, and as a result, the crystal orientation is improved. It is assumed that there is.

  Note that when the first underlayer 14 or the second underlayer 15 is formed by sputtering, a rare gas atmosphere is used by using a material containing nitrogen as a sputtering target instead of forming a film in a rare gas atmosphere containing nitrogen gas. You may form into a film in.

  Furthermore, the second underlayer 15 may be composed of a plurality of layers. In this case, it is preferable to set the total thickness of the plurality of layers to the same thickness as that of one layer. The enlargement of the crystal grains constituting the first underlayer 15 can be suppressed, and the enlargement of the crystal grains of the first magnetic layer 16 and the second magnetic layer 19 can be suppressed.

  The second underlayer 15 may be made of the same material as the first underlayer 14. In addition, although the characteristics such as the S / N ratio are further improved when the second underlayer 15 is provided, the second underlayer 15 is not necessarily provided.

  The first magnetic layer 16 is made of Co, Ni, Fe, a Co alloy, a Ni alloy, a Fe alloy, or the like. In particular, a material obtained by adding CoCr, CoCrTa, or CoCrPt and further adding B, Mo, Nb, Ta, W, Cu, and an alloy thereof to these is preferable. The thickness of the first magnetic layer 16 is set in the range of 1 nm to 10 nm, preferably in the range of 1 nm to 5 nm. The first magnetic layer 16 is epitaxially grown on the second underlayer 15 in, for example, the (110) direction, the c-axis is oriented in the in-plane direction, and the easy magnetization axis direction is the in-plane direction. A plurality of first magnetic layers 16 may be stacked. Thereby, the c-axis orientation of the first magnetic layer 16 itself and the second magnetic layer 19 can be improved.

  The nonmagnetic coupling layer 18 is made of, for example, Ru, Rh, Ir, Ru-based alloy, Rh-based alloy, Ir-based alloy, and the like, and has a film thickness of, for example, 0.4 nm to 1.5 nm (preferably 0.6 nm to 0. 9 nm). By setting the film thickness in such a range, the magnetizations of the first magnetic layer 16 and the second magnetic layer 19 can be exchange-coupled antiferromagnetically. Of these materials, in terms of lattice matching, the nonmagnetic coupling layer 18 is preferably Ru or a Ru-based alloy. Rh and Ir have an fcc structure, while Ru has an hcp structure, and Ru is close to a = 0.27 nm as compared to the lattice constant a = 0.25 nm of the CoCrPt alloy.

  Ru-based alloys include Ru, Ti, V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Rh, Pd, Ta, W, Re, Os, Ir, Pt, and alloys thereof. Or an alloy with one of them.

  The second magnetic layer 19 has a thickness set in a range of 5 nm to 30 nm and is made of Co, Ni, Fe, a Co alloy, a Ni alloy, a Fe alloy, or the like. In particular, a material obtained by adding CoCrTa or CoCrPt and further adding B, Mo, Nb, Ta, W, Cu and alloys thereof to these is preferable. Since the stacked body from the first seed layer 12 to the second magnetic layer 19 is formed by epitaxial growth, the crystallinity is good and the crystal grain size is controlled, so that medium noise is reduced.

  The material of the first magnetic layer 16 and the second magnetic layer 19 may use the same composition. When a CoCrPt alloy is used, a larger amount of Pt may be added to the second magnetic layer 19 than to the first magnetic layer 16. Even if the amount of Pt of the second magnetic layer 19 to which a larger recording magnetic field is applied is increased, the anisotropic magnetic field is increased more than the first magnetic layer 16 and the thermal stability is improved without significantly degrading the overwrite characteristics. be able to. A plurality of second magnetic layers 19 may be stacked.

The first magnetic layer 16, the residual magnetization and the film thickness of the relationship between the second magnetic layer 19, the residual magnetization Mr ₁ and a thickness t ₁ of the first magnetic layer 16, the residual magnetization Mr ₂ and the second magnetic layer 19 When expressed as the film thickness t ₂ , it is preferable to set (Mr ₂ × t ₂ > Ms ₁ × t _1. The second magnetic layer 19 close to the magnetic head corresponds to the switching position of the recording magnetic field during recording. Thus, the NLTS characteristics are improved because the recording is performed more accurately than the first magnetic layer 16.

  The protective layer 20 is formed by using a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like, and is made of, for example, diamond-like carbon (DLC), carbon nitride, amorphous carbon, or the like. The film thickness of the protective layer 20 is set to 0.5 nm to 10 nm (preferably 0.5 nm to 5 nm).

  The lubricating layer 21 is applied by using a pulling method, a spin coating method, a liquid level lowering method, and the like. For example, an organic liquid lubricant having perfluoropolyether as a main chain and a terminal group consisting of a hydroxyl group, a phenyl group, or the like is fluorinated. Use a coating solution diluted with a solvent. The film thickness of the lubricating layer 21 is set in the range of 0.5 nm to 3.0 nm. As the organic liquid lubricant, for example, ZDol (manufactured by Monte Fluos), AM3001 (manufactured by Augmont), Z25 (manufactured by Monte Fluos), or the like can be used. The lubricant is appropriately selected according to the material of the protective layer 20. When the magnetic recording medium 10 is in the form of a tape, a die coating method or the like can also be used.

  A nonmagnetic intermediate layer made of a nonmagnetic alloy having an hcp structure in which an element or an alloy M is added to a CoCr alloy may be formed between the second underlayer 15 and the first magnetic layer 16. The nonmagnetic intermediate layer has a thickness set in the range of 1 nm to 5 nm, and M is selected from Pt, B, Mo, Nb, Ta, W, Cu, and alloys thereof. The nonmagnetic intermediate layer epitaxially grows taking over the crystallinity and crystal grain size of the second underlayer 15, improves the crystallinity of the first magnetic layer 16 and the second magnetic layer 19, and distributes the crystal grain (magnetic particle) size. The width can be reduced and the c-axis orientation in the in-plane direction (direction parallel to the substrate surface) can be promoted.

  According to the present embodiment, the first underlayer 14 of the magnetic recording medium 10 having the first magnetic layer 16 and the second magnetic layer 19 that are antiferromagnetically exchange-coupled with the nonmagnetic coupling layer 18 interposed therebetween is nitrogen gas. By forming a film using Cr or a Cr-based alloy having a bcc crystal structure by a sputtering method in a rare gas atmosphere containing a coercive force, the coercive force squareness ratio can be greatly increased and the resolution and the S / N ratio can be increased. Can be improved.

  Next, examples of the present embodiment and comparative examples will be described.

[Examples 1 to 5 and Comparative Examples 1 to 5]
Magnetic disks having the following configurations were manufactured as Examples 1 to 5 and Comparative Examples 1 to 5.
Textured glass substrate / Cr ₅₀ Ti ₅₀ film (25 nm) / Al ₅₀ Ru ₅₀ film (10 nm) / first underlayer (3 nm) / second underlayer (3 nm) / Co ₉₀ Cr ₁₀ film (2 nm) / Ru film (0.8 nm) / Co ₆₀ Cr ₁₈ Pt ₁₁ B ₈ Cu ₃ film (16 nm) / DLC film (5.5 nm) / AM3001 lubrication layer (1.5 nm). The numerical values in parentheses indicate the film thickness.

Here, each layer excluding the lubricating layer is formed using a DC magnetron sputtering apparatus, and before the Cr ₅₀ Ti ₅₀ film (25 nm) is formed, the inside of the sputtering apparatus is evacuated to 4 × 10 ⁻⁵ Pa or less, and then texture treatment is performed. The glass substrate was heat-treated at a temperature of 180 ° C. Except for the DLC film forming process, the pressure in the sputtering apparatus was set to 0.67 Pa, and the film was formed in an Ar gas atmosphere except for the first underlayer forming process of the magnetic disk of the example. In addition, the numerical value which shows the composition amount of each layer is shown by atomic%, and it is the same in this specification hereafter.

  FIG. 2 is a diagram illustrating the configuration and characteristics of the first and second underlayers of the magnetic disks according to Examples 1 to 5 and Comparative Examples 1 to 5. In FIG. 2, the numerical value indicating the element concentration (atomic%) is shown in front of the element for the composition of each layer.

  Referring to FIG. 2, in the magnetic disks of Examples 1 to 6, the first underlayer was formed in an atmosphere in which Cr or a CrMo alloy was added to Ar gas and 0.1% by volume of nitrogen gas, while comparison was made. In the magnetic disks of Examples 1 to 6, the first underlayer was formed by depositing the metal material of Examples 1 to 6 in Ar gas to which nitrogen gas was not added. The second underlayers of Examples 1 to 6 and Comparative Examples 1 to 6 are made of a CrMo alloy or a CrW alloy shown in FIG. Hereinafter, for convenience of explanation, a film formed in an atmosphere to which nitrogen gas has been added is shown with “(N)” added after the composition.

  When Examples 1 to 6 and Comparative Examples 1 to 6 were compared, Examples 1 to 6 in which the first underlayer was formed in an Ar gas atmosphere to which 0.1% by volume of nitrogen gas was added had an Ar gas atmosphere. The coercivity squareness ratio and the resolution are improved for each of Comparative Examples 1 to 6 formed therein. That is, it can be seen that the resolution can be improved by adding nitrogen gas when forming the first underlayer.

Specifically, in Example 1 (first underlayer / second underlayer = Cr (N) film / Cr ₇₅ Mo ₂₅ film, the parentheses up to Example 5 and Comparative Example 5 are the first underlayer / first underlayer). 2 shows the structure of the underlayer.) And Comparative Example 1 (Cr film / Cr ₇₅ Mo ₂₅ film) are compared with Example 1 in which nitrogen gas is added, compared to Comparative Example 1 in which nitrogen gas is not added. It can be seen that the squareness ratio is increased by 0.05 and the resolution is improved by 1%.

Further, in comparison with Example 1, Example 4 (Cr (N) film / Cr _92.5 W _7.5 film) in which the second underlayer was replaced with a Cr _92.5 W _7.5 film instead of the Cr ₇₅ Mo ₂₅ film and Comparative Example 4 (Cr Film / Cr _92.5 W _7.5 film), in Example 4, in which nitrogen gas was added, the coercive force squareness ratio increased by 0.09 compared to Comparative Example 4 in which nitrogen gas was not added, and the resolution was 2.1. % Increase.

Further, in contrast to Example 1, the first underlayer is Cr ₉₅ Mo ₅ (N) film instead of Cr (N) film. Example 5 (Cr ₉₅ Mo ₅ (N) film / Cr ₇₅ Mo ₂₅ film) Also in Comparative Example 5 (Cr ₉₅ Mo ₅ film / Cr ₇₅ Mo ₂₅ film), Example 5 to which nitrogen gas was added had a coercive force squareness ratio of 0.05 compared to Comparative Example 5 to which no nitrogen gas was added. It can be seen that the resolution is improved by 1%.

  From the above, it can be seen that forming the first underlayer made of Cr or CrMo in an Ar gas atmosphere containing nitrogen gas can increase the coercivity squareness ratio and improve the resolution.

  The magnetostatic characteristics such as the coercive force and the coercive force squareness ratio are measured with a vibrating sample magnetometer (VSM, maximum applied magnetic field 795.7 kA / m), and the coercive force and the coercive force are measured from the hysteresis loop of the obtained magnetic disk. Static magnetic properties such as coercivity squareness ratio were obtained.

  FIG. 3 is a diagram showing a hysteresis loop of the magnetic disk. Referring to FIG. 3, the coercive force squareness ratio S * is calculated from the magnetic field quantity Hr at the intersection of the tangent line of the hysteresis loop at -Hc (or Hc) and the straight line extending in parallel to the H axis from the residual magnetization Mr. = Hr / Hc.

Further, for measurement of resolution, and electromagnetic conversion characteristics such as average output, overwrite, S / Nm, and Siso / Nm in the following examples, a composite magnetic head having an inductive recording element and a GMR reproducing element was used. The peripheral speed is 12.6 m / s, the average output is the average output Siso at a linear recording density of 89 kFCI, the resolution is resolution (%) = (average output at 89 kFCI) / (average output at 357 kFCI) × 100, the overwrite is After measuring the output V ₁ at 89 kFCI, a 714 kFCI signal was written and the remaining 89 kFCI output V ₂ was measured, and 10 × log (V ₂ / V ₁ ) was overwritten (dB). S / Nm and Siso / Nm are the ratio of the average output S at 357 kFCI, the average output Siso at 89 kFCI, and the medium noise Nm, respectively, 10 × log (S / Nm), 10 × log (Siso / Nm) ( dB).

[Example 6]
Next, the nitrogen gas addition amount added to the Ar gas atmosphere when forming the first underlayer in Example 1 is in the range of 0.00 vol% to 0.50 vol% every 0.05 vol%. FIG. 4 to FIG. 10 show the characteristics of the magnetic disk of Example 6 formed differently. In Example 6, the Cr ₇₅ Mo ₂₅ film of the second underlayer is formed in an Ar gas atmosphere to which no nitrogen gas is added.

  In addition, the case where the amount of nitrogen gas added to the first underlayer is 0.00 vol%, that is, no nitrogen gas is added is shown for comparison. Each characteristic line in the figure is obtained by interpolating a characteristic value every 0.05% by volume.

The structure of the magnetic disk of Example 6 is as follows: textured glass substrate / Cr ₅₀ Ti ₅₀ film (25 nm) / Al ₅₀ Ru ₅₀ film (10 nm) / Cr (N) film (3 nm) / Cr ₇₅ Mo ₂₅ film (3 nm) / Co ₉₀ Cr ₁₀ film (2 nm) / Ru film (0.8 nm) / Co ₆₀ Cr ₁₈ Pt ₁₁ B ₈ Cu ₃ film (16 nm) / DLC film (5.5 nm) / lubricating layer (1.5 nm) . The other film forming conditions are the same as those in Example 1.

  FIG. 4 is a graph showing the relationship between the coercive force squareness ratio and the nitrogen gas addition amount in Example 6. Referring to FIG. 4, the Cr (N) film in which the first underlayer of the magnetic disk of Example 6 was formed in an atmosphere containing nitrogen gas abruptly added with a small amount of 0.05% by volume of nitrogen gas. The coercive force squareness ratio increases, shows a maximum value at an addition amount of about 0.10% by volume, and increases by 0.06 from 0.72 when nitrogen gas is not added. It can also be seen that the coercive force squareness ratio is higher and more stable when nitrogen gas is added up to 0.05% by volume than when nitrogen gas is not added. Thus, it can be seen that the coercivity squareness ratio can be significantly increased by adding a small amount of nitrogen gas to the first underlayer.

  FIG. 5 is a graph showing the relationship between the coercive force and the amount of nitrogen gas added in Example 6. Referring to FIG. 5, the coercive force of the magnetic disk of Example 6 decreases as the amount of nitrogen gas added increases. Compared to the case where nitrogen gas is not added, even when added up to 0.50% by volume, it is about 22 kA / m (278 Oe), and it has been confirmed that this decrease in coercive force does not affect the thermal stability. . Moreover, it is possible to suppress or prevent the decrease in the coercive force by setting the substrate heating temperature high. According to the study of the present inventor, it has been confirmed that when the amount of nitrogen gas added is greater than 0.50% by volume, the rate of decrease in coercive force increases, and when the amount exceeds 0.75% by volume, it rapidly decreases. Yes. Therefore, from the viewpoint of production stability, the amount of nitrogen gas added is preferably 0.50% by volume or less.

FIG. 6 is a graph showing the relationship between the exchange coupling magnetic field and the amount of nitrogen gas added in Example 6. As shown in FIG. 3, the exchange coupling magnetic field H _EX is the magnetic field at the center of the loop formed by the minor loop ML indicated by the broken line on the positive magnetic field side at point D and the major loop indicated by the solid line. In the measurement, the applied magnetic field H is once swept to the vicinity of the point D, and then the applied magnetic field H is increased in the same direction to obtain a minor loop ML. A coupled magnetic field is also obtained on the negative magnetic field side of point B. The exchange coupling magnetic field is a magnetic field in which the first magnetic layer and the second magnetic layer are applied to each other. When the exchange coupling magnetic field is large, the thermal stability is improved. It becomes difficult to switch, and the overwrite characteristics and S / Nm ratio deteriorate.

  Referring to FIG. 6, the exchange coupling magnetic field of the magnetic disk of Example 6 rapidly decreases with the addition of a small amount of nitrogen gas, and is almost constant with the addition amount of 0.05% by volume or more. This shows that the exchange coupling magnetic field can be controlled by the amount of nitrogen gas added. The nitrogen gas addition amount may be selected using an S / Nm ratio described later as an index.

  FIG. 7 is a graph showing the relationship between the average output of Example 6 and the amount of nitrogen gas added. Referring to FIG. 7, the average output of the magnetic disk of Example 6 is substantially constant with respect to the amount of nitrogen gas added in the range of more than 0.00 volume% and 0.50 volume or less. Thus, it can be easily assumed that the addition of nitrogen gas does not affect the output, and the in-plane orientation does not change due to the addition of nitrogen gas to the first underlayer.

  FIG. 8 is a graph showing the relationship between the resolution of Example 6 and the amount of nitrogen gas added. Referring to FIG. 8, the resolution of the magnetic disk of Example 6 is increased by adding a small amount of nitrogen gas of 0.05% by volume or less, and when it is 0.50% by volume or less, nitrogen gas is not added. In comparison, it can be seen that it has increased substantially. As shown in FIG. 5, it can be easily estimated that the resolution increases despite the coercive force gradually decreasing, because the coercive force squareness ratio contributes to the improvement of the resolution.

  FIG. 9 is a graph showing the relationship between the overwrite characteristics and the nitrogen gas addition amount in Example 6. Referring to FIG. 9, the overwrite characteristics of the magnetic disk of Example 6 are greatly improved by adding a small amount of nitrogen gas of 0.05% by volume or less. The coercive force shown in FIG. 5 gradually decreases in the range of the amount of nitrogen gas added, and is presumed to be caused by the decrease in the exchange coupling magnetic field shown in FIG. 6 rather than the coercive force, and is about 0.05% by volume. It can be inferred that the addition of nitrogen gas reduced the exchange coupling magnetic field and as a result improved the overwrite characteristics.

  Furthermore, when the amount of nitrogen gas added is increased, the overwrite characteristics are further improved. This is considered to be caused by a decrease in coercive force in addition to the effect of decreasing the exchange coupling magnetic field.

  FIG. 10 is a graph showing the relationship between the S / Nm ratio and the amount of nitrogen gas added in Example 6. Referring to FIG. 10, the S / Nm ratio of the magnetic disk of Example 6 is greatly improved by adding a small amount of nitrogen gas of 0.05% by volume or less, and even with a nitrogen gas addition amount of 0.50% by volume. It can be seen that the S / Nm ratio can be improved by the addition of nitrogen gas of 0.20% by volume or less, which is 0.2 dB higher than when no nitrogen gas is added. Further, from FIG. 10, as compared with the case where nitrogen gas is not added, a significant improvement in the S / Nm ratio is recognized even when a small amount of nitrogen gas is added, for example, 0.01% by volume. It turns out that it can be fully expected.

  From FIG. 4 to FIG. 9 shown so far, the resolution and overwrite characteristics are improved due to the increase in the coercivity squareness ratio and the decrease in the exchange coupling magnetic field due to the addition of nitrogen gas to the first underlayer. As a result, it is presumed that the S / Nm ratio was improved.

[Example 7]
Next, in Example 1, the characteristics of the magnetic disk of Example 7 in which the Cr (N) film of the first underlayer was varied in the range of 1.0 nm to 6.0 nm every 1.0 nm. Is shown in FIG. 11 and FIG. The configuration of the magnetic disk of Example 7 is the same as that of Example 6 except for the film thickness of the Cr (N) film. For comparison, the case where no Cr (N) film is provided is shown in FIGS. 11 and 12 with a film thickness of 0.0 nm.

  FIG. 11 is a graph showing the relationship between the coercive force squareness ratio and the Cr (N) film thickness in Example 7. Referring to FIG. 11, the coercive force squareness ratio of the magnetic disk of Example 7 is smaller than that in the case where the Cr (N) film is not provided even if the Cr (N) film is a thin film having a thickness of 0.5 nm. It can also be seen that It gradually increases when the film thickness is 1 nm or more. Therefore, it can be seen that the Cr (N) film needs to have a thickness of 0.5 nm or more.

  FIG. 12 is a graph showing the relationship between the Siso / Nm ratio and the Cr (N) film thickness in Example 7. Referring to FIG. 12, the Siso / Nm ratio of the magnetic disk of Example 7 takes a maximum value when the film thickness of the Cr (N) film is about 1.5 nm, and Cr is in the range of 0.5 nm to 6.0 nm. (N) It turns out that it is improving rather than the case where a film | membrane is not provided. Therefore, it can be seen that the thickness of the Cr (N) film may be selected in the range of 0.5 nm to 6.0 nm in combination with the result of FIG.

[Examples 8 and 9]
Next, in Example 1, the amount of nitrogen gas added to the Ar gas atmosphere when forming the Cr (N) film for the first underlayer and the Cr ₇₅ Mo ₂₅ (N) film for the second underlayer. And the same amount, and in Example 8 formed differently in the range of 0.00 vol% to 0.50 vol%, and the first underlayer is not added with nitrogen gas but added only to the second underlayer. Thus, the magnetic disk of Example 9 formed in a range of 0.00 volume% to 0.50 volume% was manufactured. That is, in Example 8, the first underlayer / second underlayer = Cr (N) film (3 nm) / Cr ₇₅ Mo ₂₅ (N) film (3 nm), and in Example 9, Cr film (3 nm) / Cr ₇₅ Mo ₂₅ The (N) film (3 nm) was used, and the other configuration was the same as in Example 1.

  FIG. 13 is a graph showing the relationship between the coercivity squareness ratio and the amount of nitrogen gas added in Example 8 and Example 9. Referring to FIG. 13, the coercive force squareness ratios of Example 8 and Example 9 show substantially the same characteristic values, and in the range where the nitrogen gas addition amount is more than 0.0 and 0.28% by volume or less, It is higher than when no gas is added. However, when nitrogen gas is added during the formation of the second underlayer as described above, the coercive force squareness ratio is lower than that in FIG. 4 in which nitrogen gas is added only to the first underlayer. It can be seen that the range of the nitrogen gas addition amount is also narrow.

FIG. 14 is a graph showing the relationship between the average output of Example 8 and Example 9 and the amount of nitrogen gas added. Referring to FIG. 14, the average output of Example 8 and Example 9 is almost the same as the case where nitrogen gas is not added in the range where the amount of nitrogen gas added is more than 0.0 and 0.10% by volume or less. When it exceeds 0.10% by volume, it decreases rapidly. It can be seen that when the nitrogen is excessively added to the Cr ₇₅ Mo ₂₅ (N) film of the second underlayer, the in-plane orientation of the first magnetic layer and the second magnetic layer is lowered. Thus, it can be seen that the amount of nitrogen added to the second underlayer is preferably set in the range of 0.00 volume% or more and 0.10 volume% or less.

FIG. 15 is a diagram showing the relationship between the resolution and the nitrogen gas addition amount in Examples 8 and 9, and FIG. 16 is a diagram showing the relationship between the S / Nm ratio and the nitrogen gas addition amount. Referring to FIGS. 15 and 16, the resolution of Example 8 and Example 9 is 0.2 vol% or less in the resolution of the Cr ₇₅ Mo ₂₅ (N) film of the second underlayer, and the S / Nm ratio. It can be seen that the case where nitrogen gas is added in the range of 0.10% by volume or less is better than the case where nitrogen gas is not added.

  From the results of FIGS. 13 to 16, it can be seen that the amount of nitrogen gas added to the second underlayer is preferably selected from the range of 0.00 volume% or more and 0.10 volume% or less.

  Next, specific examples of the magnetic recording medium according to the embodiment of the present invention will be listed with reference to the drawings. Hereinafter, in the figure, the same reference numerals are assigned to portions corresponding to the portions described above, and description thereof will be omitted as appropriate.

  First, the magnetic recording medium according to the first example of the embodiment of the invention has the configuration shown in FIG. That is, referring to FIG. 1, the magnetic recording medium 10 according to the first example includes a substrate 11, a first seed layer 12, a second seed layer 13, a first underlayer 14, a second lower layer on the substrate 11. The base layer 15, the first magnetic layer 16, the nonmagnetic coupling layer 18, the second magnetic layer 19, the protective layer 20, and the lubricating layer 21 are sequentially stacked.

  The first underlayer 14 is made of Cr or a Cr-based alloy having a bcc crystal structure and nitrogen. The first underlayer 14 is made of a material made of Cr or a Cr-based alloy having a bcc crystal structure, and the amount of nitrogen gas added to the rare gas is, for example, 0.01 volume% to 0.50 volume% (preferably 0.00. It is obtained by forming a film in an atmospheric gas set in the range of 05 volume% to 0.50 volume%).

  The second underlayer 15 is made of Cr or a Cr alloy having a bcc crystal structure, or Cr or a Cr alloy and nitrogen. The second underlayer 15 is made of a material made of Cr or a Cr-based alloy having a bcc crystal structure, and the amount of nitrogen gas added to the rare gas is, for example, in the range of 0.00 volume% or more and 0.10 volume% or less. It is obtained by forming a film in a set atmospheric gas. Furthermore, the second underlayer 15 may not substantially contain nitrogen.

  FIG. 17 is a cross-sectional view of a magnetic recording medium according to the second example of the present embodiment. Referring to FIG. 17, the magnetic recording medium 20 according to the second example includes a substrate 11 and a first seed layer 12, a second seed layer 13, a first A underlayer 14A, and a first B underlayer 14B on the substrate 11. The second underlayer 15, the first magnetic layer 16, the nonmagnetic coupling layer 18, the second magnetic layer 19, the protective layer 20, and the lubricating layer 21 are sequentially stacked.

  Each of the first A underlayer 14A and the first B underlayer 14B is made of the same material as the first underlayer 14 of the magnetic recording medium according to the first example shown in FIG. The total thickness of the first A underlayer 14A and the first B underlayer 14B is preferably set to the same thickness as when the first underlayer is a single layer. By reducing the thickness of each of the first A underlayer 14A and the first B underlayer 14B, enlargement of crystal grains in the first A underlayer 14A and the first B seed layer 12B is suppressed, and as a result, the first magnetic layer 16 and The enlargement of the crystal grains of the second magnetic layer 19 can be suppressed.

  As an example of the combination of the first A underlayer 14A and the first B underlayer 14B, the first A underlayer 14A and the first B underlayer 14B are made of a Cr-based alloy containing nitrogen similar to the magnetic recording medium according to the first example. The Cr-based alloy is a Cr-based alloy in which the first B underlayer 14B has a higher additive element concentration in atomic% than the first A underlayer 14A. With this configuration, the lattice matching between the first A underlayer 14A and the first B underlayer 14B is improved, and at the same time, the lattice matching between the first B underlayer 14B and the second underlayer 15 is improved. Can be improved. As a result, the crystallinity of the second underlayer 15 can be improved, and consequently the crystallinity of the first magnetic layer 16 and the second magnetic layer 19 can be improved. Furthermore, in the magnetic recording medium 20, it is preferable that the second underlayer 15 is made of a Cr-based alloy that does not substantially contain nitrogen.

  FIG. 18 is a cross-sectional view of a magnetic recording medium according to the third example of the present embodiment. Referring to FIG. 18, the magnetic recording medium 30 according to the third example includes a substrate 11, a first seed layer 12, a second seed layer 13, a third underlayer 31, and a first underlayer 14 on the substrate 11. The second underlayer 15, the first magnetic layer 16, the nonmagnetic coupling layer 18, the second magnetic layer 19, the protective layer 20, and the lubricating layer 21 are sequentially stacked.

  The third underlayer 31 is made of a Cr film or a Cr alloy film having a bcc crystal structure. The Cr-based alloy film having a bcc crystal structure is made of the same material as the Cr-based alloy of the first underlayer 14. The third underlayer 31 is obtained by forming a Cr film or a Cr-based alloy material in a rare gas atmosphere by a sputtering method. As described above, by providing the third base layer 31 that does not contain nitrogen as the base of the first base layer 14, the crystallinity of the initial growth layer of the first base layer 14 can be improved. Further, in the magnetic recording medium 30, it is preferable that the second underlayer 15 is made of a Cr-based alloy substantially containing nitrogen.

  FIG. 19 is a cross-sectional view of a magnetic recording medium according to the fourth example of the present embodiment. Referring to FIG. 19, the magnetic recording medium 35 according to the fourth example includes a substrate 11 and a first seed layer 12, a second seed layer 13, a first underlayer 14, and a second A underlayer 15A on the substrate 11. The second B underlayer 15B, the first magnetic layer 16, the nonmagnetic coupling layer 18, the second magnetic layer 19, the protective layer 20, and the lubricating layer 21 are sequentially stacked.

  Each of the second A underlayer 15A and the second B underlayer 15B is made of Cr or a Cr-based alloy having a bcc crystal structure, like the second underlayer 15 of the magnetic recording medium according to the first example shown in FIG. Or it consists of Cr or a Cr-type alloy and nitrogen. The total thickness of the second A underlayer 15A and the second B underlayer 15B is preferably set to the same thickness as that of the single second underlayer. By setting in this way, each of the 2A base layer 15A and the 2B base layer 15B is thinned, and the enlargement of each crystal particle is suppressed. As a result, the enlargement of the magnetic particles of the first magnetic layer 16 and the second magnetic layer 19 can be suppressed.

  As an example of the combination of the second A underlayer 15A and the second B underlayer 15B, each of the 2A underlayer 15A and the 2B underlayer 15B is made of a Cr-based alloy substantially not containing nitrogen. The Cr-based alloy is a Cr-based alloy in which the second B underlayer 15B has a higher additive element concentration in atomic% than the second A underlayer 15A. With this configuration, the lattice matching between the second A underlayer 15A and the second B underlayer 15B is improved, and at the same time, the lattice matching between the second B underlayer 15B and the first magnetic layer 16 is improved. can do. As a result, the crystallinity of the first magnetic layer 16 and the second magnetic layer 19 can be improved.

  Next, a magnetic memory device according to another embodiment of the present invention will be described. FIG. 20 is a diagram showing a main part of a magnetic memory device according to another embodiment of the present invention.

  Referring to FIG. 20, the magnetic storage device 40 generally includes a housing 41. In the housing 41, a hub 42 driven by a spindle (not shown), a magnetic recording medium 43 fixed to the hub 42 and rotated, an actuator unit 44, and attached to the actuator unit 44 in the radial direction of the magnetic recording medium 43. A moving arm 45, a suspension 46, and a magnetic head 48 supported by the suspension 46 are provided. The magnetic head 48 is a composite head composed of a reproducing head such as an MR element (magnetoresistive element), a GMR element (giant magnetoresistive element), or a TMR element (tunneling magnetic effect element) and an inductive recording head. Consists of. The basic configuration of the magnetic storage device 40 is well known, and detailed description thereof is omitted in this specification.

  In the magnetic storage device 40, the magnetic recording medium 43 is one of the magnetic recording media according to the above-described embodiments, for example, the magnetic recording media according to the first to fourth examples. The magnetic recording medium 43 has an excellent coercive force squareness ratio, resolution, overwrite characteristics, and S / N ratio, and also has excellent thermal stability. As a result, the magnetic storage device 40 having excellent thermal stability and S / N ratio can be realized.

  The basic configuration of the magnetic storage device 40 is not limited to that shown in FIG. 20, and the magnetic head 48 is not limited to the configuration described above.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the present invention described in the claims.・ Change is possible.

  For example, the magnetic recording medium of the present invention may be configured by combining the magnetic recording media according to the first to fourth examples described in the embodiments. In the above embodiment, a magnetic disk is described as an example of the magnetic recording medium, but the present invention can be applied to a magnetic tape.

In addition, the following additional notes are disclosed regarding the above description.
(Appendix 1) a substrate,
An underlayer formed on the substrate;
A first magnetic layer formed on the underlayer;
A nonmagnetic coupling layer formed on the first magnetic layer;
A second magnetic layer formed on the nonmagnetic coupling layer,
In the magnetic recording medium, the first magnetic layer and the second magnetic layer are exchange-coupled, and the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other when no external magnetic field is applied. There,
The magnetic recording medium according to claim 1, wherein the underlayer is made of Cr or Cr-based alloy having a bcc crystal structure and containing nitrogen.
(Supplementary note 2) The magnetic recording medium according to supplementary note 1, wherein the underlayer is formed in an atmosphere gas containing nitrogen gas of 0.01% by volume or more and 0.50% by volume or less.
(Additional remark 3) Between the said underlayer and the said 1st magnetic layer, the Cr or Cr type | system | group alloy which has a bcc crystal structure, or the other underlayer which contains this Cr or Cr type alloy and contains nitrogen is formed The magnetic recording medium according to appendix 1 or 2, wherein
(Supplementary note 4) The magnetic recording medium according to supplementary note 3, wherein the other underlayer is made of a material that does not substantially contain nitrogen.
(Additional remark 5) Said other underlayer is formed in the atmospheric gas containing the nitrogen gas of 0.00 volume% or more and 0.10 volume% or less of Cr or Cr-type alloy which has a bcc crystal structure. The magnetic recording medium according to supplementary note 3, characterized by:
(Additional remark 6) The nitrogen concentration in atmospheric gas at the time of forming the said other underlayer is set lower than the nitrogen concentration in atmospheric gas at the time of forming the said underlayer Magnetic recording media.
(Appendix 7) The Cr-based alloy is an alloy composed of at least one additive element of the group consisting of Mo, W, V, and Ti, and Cr. A magnetic recording medium according to claim 1.
(Supplementary note 8) The magnetic recording medium according to supplementary note 7, wherein the other underlayer has a higher concentration in atomic% of the additive element than the underlayer.
(Supplementary note 9) The magnetic layer according to supplementary note 7 or 8, wherein the underlayer includes two layers, and the layer on the first magnetic layer side has a higher concentration of the additive element in atomic% than the layer on the substrate side. recoding media.
(Supplementary note 10) The supplementary note 7 or 8, wherein the other underlayer includes two layers, and the first magnetic layer side layer has a higher concentration of the additive element in atomic% than the substrate side layer. Magnetic recording media.
(Additional remark 11) The magnetic recording medium as described in any one of Additional remarks 3-10 characterized by further providing the other underlayer which consists of Cr or a Cr-type alloy immediately under the said underlayer.
(Additional remark 12) The magnetic recording medium as described in any one of additional remarks 1-11 characterized by setting the film thickness of the said base layer in the range of 0.5 nm or more and 6.0 nm or less.
(Supplementary Note 13) A seed layer is further provided between the substrate and the base layer,
The magnetic recording medium according to any one of appendices 1 to 12, wherein the seed layer is made of a nonmagnetic amorphous metal or an alloy having a B2 structure.
(Supplementary note 14) The magnetic layer according to supplementary note 13, wherein the seed layer is formed by depositing a layer made of a nonmagnetic amorphous metal and a layer made of an alloy having a B2 structure in this order from the substrate side. recoding media.
(Supplementary note 15) The magnetic recording medium according to supplementary note 13 or 14, wherein the amorphous metal is one of a group consisting of NiP, CoW, AlTi, and CrTi.
(Supplementary note 16) The magnetic recording medium according to supplementary note 13 or 14, wherein the alloy having the B2 structure is any one of a group consisting of AlRu, NiAl, and FeAl.
(Supplementary Note 17) The first magnetic layer is any one of CoCr, CoCrPt, CrCr, or CoCrPt added with any one of the group consisting of B, Mo, Nb, Ta, W, Cu, and alloys thereof. The magnetic recording medium according to any one of supplementary notes 1 to 16, characterized in that:
(Supplementary Note 18) The first magnetic layer is made of any one of materials obtained by adding any one of B, Mo, Nb, W, Cu, and alloys thereof to CoCrTa, CrCrTa. The magnetic recording medium according to any one of Supplementary notes 1 to 16.
(Supplementary Note 19) The second magnetic layer is made of a ferromagnetic material in which CoCrPt or CoCrPt is added with any one of the group consisting of B, Mo, Nb, Ta, W, Cu and alloys thereof. The magnetic recording medium according to any one of Supplementary notes 1 to 18, which is a feature.
(Appendix 20) a substrate;
An underlayer formed on the substrate;
Other underlayers formed on the underlayer,
A first magnetic layer formed on the other underlayer;
A nonmagnetic coupling layer formed on the first magnetic layer;
A second magnetic layer formed on the nonmagnetic coupling layer,
In the magnetic recording medium, the first magnetic layer and the second magnetic layer are exchange-coupled, and the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other when no external magnetic field is applied. There,
The underlayer is made of Cr having a bcc crystal structure or a Cr-based alloy and nitrogen,
The other underlayer is made of Cr or Cr-based alloy having a bcc crystal structure, or the Cr or Cr-based alloy and nitrogen,
The magnetic recording medium, wherein the underlayer contains more nitrogen than other underlayers.
(Supplementary note 21) a disk-shaped substrate;
A seed layer made of any one of the group consisting of AlRu, NiAl, and FeAl formed on the substrate;
An underlayer formed on the seed layer in an atmosphere gas containing Cr or Cr-based alloy having a bcc crystal structure in an amount of 0.01% by volume or more and 0.50% by volume or less of nitrogen gas;
On the underlayer, another underlayer formed in an atmosphere gas containing nitrogen gas of 0.00 vol% or more and 0.10 vol% or less of Cr or Cr-based alloy having a bcc crystal structure;
A first magnetic layer formed on the other underlayer;
A nonmagnetic coupling layer formed on the first magnetic layer;
A second magnetic layer formed on the nonmagnetic coupling layer,
A magnetic disk in which the first magnetic layer and the second magnetic layer are exchange-coupled and the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other when no external magnetic field is applied.
(Supplementary Note 22) A substrate, an underlayer formed on the substrate, a first magnetic layer formed on the underlayer, a nonmagnetic coupling layer formed on the first magnetic layer, A second magnetic layer formed on the nonmagnetic coupling layer,
In the magnetic recording medium, the first magnetic layer and the second magnetic layer are exchange-coupled, and the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other when no external magnetic field is applied. A manufacturing method comprising:
Forming the base layer on the substrate;
The method for producing a magnetic recording medium is characterized in that in the step of forming the underlayer, a Cr or Cr-based alloy having a bcc crystal structure is formed in an atmosphere gas containing nitrogen gas.
(Supplementary Note 23) A step of further forming another underlayer between the underlayer and the first magnetic layer,
25. The magnetic recording according to appendix 22, wherein in the forming of the other underlayer, Cr or a Cr-based alloy having a bcc crystal structure is formed in an atmospheric gas containing 0.10% by volume or less of nitrogen gas. A method for manufacturing a medium.
(Supplementary note 24) The method for manufacturing a magnetic recording medium according to supplementary note 23, wherein the step of forming the underlayer comprises forming a film in an atmospheric gas containing 0.01% to 0.50% by volume of nitrogen gas. .
(Additional remark 25) The said Cr-type alloy which has the said bcc crystal structure is an alloy which consists of at least 1 sort (s) of additional elements among the groups which consist of Mo, W, V, and Ti, and additional notes 22-24 characterized by the above-mentioned. A method for manufacturing a magnetic recording medium according to any one of the above.
(Supplementary Note 26) The Cr-based alloy having the bcc crystal structure is an alloy made of Cr and at least one additive element out of the group consisting of Mo, W, V, and Ti.
The underlayer and the other underlayer contain the same additive element,
26. The method of manufacturing a magnetic recording medium according to any one of appendices 23 to 25, wherein the concentration of the additive element in atomic% is higher in the other underlayer than in the underlayer.
(Supplementary note 27) The method for manufacturing a magnetic recording medium according to any one of supplementary notes 21 to 26, wherein B is further added to the Cr or Cr-based alloy.
(Supplementary Note 28) The supplementary notes 23 to 27 are characterized in that in the step of forming the other underlayer, the film is formed in a rare gas atmosphere containing at least one of the group of He, Ne, Ar, Kr, and Xe. A method for manufacturing a magnetic recording medium according to any one of the above.
(Supplementary note 29) The method for manufacturing a magnetic recording medium according to any one of supplementary notes 23 to 28, wherein a film thickness of the underlayer is set in a range of 0.5 nm to 6.0 nm.
(Supplementary note 30) The magnetic recording medium according to any one of supplementary notes 23 to 28, further comprising a step of forming a seed layer having a B2 structure on the substrate before forming the underlayer. Manufacturing method.
(Supplementary note 31) The magnetic recording medium according to any one of supplementary notes 1 to 20, or the magnetic recording medium produced by the production method according to any one of supplementary notes 22 to 30, and recording / reproducing means, A magnetic storage device comprising:
(Additional remark 32) A magnetic disk apparatus provided with the magnetic disk of Additional remark 21, and a recording / reproducing means.

It is sectional drawing of the magnetic-recording medium produced with the manufacturing method which concerns on this invention. It is a figure which shows the structure and characteristic of the 1st and 2nd base layer of the magnetic disc which concerns on an Example and a comparative example. It is a figure which shows the hysteresis loop of magnetization of a magnetic disk. It is a figure which shows the relationship between the coercive force squareness ratio of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between the coercive force of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between the exchange coupling magnetic field of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between the average output of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between the resolution | decomposability of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between the overwrite characteristic of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between S / Nm ratio of Example 6, and nitrogen gas addition amount. It is a figure which shows the relationship between the coercive force squareness ratio of Example 7, and a Cr (N) film | membrane film thickness. It is a figure which shows the relationship between Siso / Nm ratio of Example 7, and a Cr (N) film | membrane film thickness. It is a figure which shows the relationship between coercive force squareness ratio of Example 8 and Example 9, and nitrogen gas addition amount. It is a figure which shows the relationship between the average output of Example 8 and Example 9, and nitrogen gas addition amount. It is a figure which shows the relationship between the resolution | decomposability of Example 8 and Example 9, and nitrogen gas addition amount. It is a figure which shows the relationship between S / Nm ratio of Example 8 and Example 9, and nitrogen gas addition amount. It is sectional drawing of the magnetic-recording medium based on the 2nd example of embodiment. It is sectional drawing of the magnetic-recording medium based on the 3rd example of embodiment. It is sectional drawing of the magnetic-recording medium based on the 4th example of embodiment. It is a figure which shows the principal part of the magnetic storage apparatus which concerns on other embodiment of this invention.

Explanation of symbols

10, 20, 30, 35, 43 Magnetic recording medium 11 Substrate 12 First seed layer 13 Second seed layer 14 First underlayer 15 Second underlayer 16 First magnetic layer 18 Nonmagnetic coupling layer 19 Second magnetic layer 20 Protective layer 21 Lubricating layer 40 Magnetic storage device

Claims (17)

A substrate,
An underlayer formed on the substrate;
A first magnetic layer formed on the underlayer;
A nonmagnetic coupling layer formed on the first magnetic layer;
A second magnetic layer formed on the nonmagnetic coupling layer,
In the magnetic recording medium, the first magnetic layer and the second magnetic layer are exchange-coupled, and the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other when no external magnetic field is applied. There,
The magnetic recording medium according to claim 1, wherein the underlayer is made of Cr or Cr-based alloy having a bcc crystal structure and containing nitrogen.   2. The magnetic recording medium according to claim 1, wherein the underlayer is formed in an atmospheric gas containing nitrogen gas of 0.01 volume% or more and 0.50 volume% or less.   Between the underlayer and the first magnetic layer, Cr or a Cr-based alloy having a bcc crystal structure, or another underlayer containing the Cr or Cr-based alloy and containing nitrogen is formed. The magnetic recording medium according to claim 1 or 2.   4. The magnetic recording medium according to claim 3, wherein the other underlayer is made of a material that does not substantially contain nitrogen.   The other underlayer is formed of Cr or a Cr-based alloy having a bcc crystal structure in an atmosphere gas containing 0.00 vol% or more and 0.10 vol% or less of nitrogen gas. The magnetic recording medium according to claim 3.   The Cr-based alloy is an alloy composed of Cr and at least one additive element selected from the group consisting of Mo, W, V, and Ti. The magnetic recording medium described.   The magnetic recording medium according to claim 6, wherein the other underlayer has a higher concentration in atomic% of the additive element than the underlayer.   8. The magnetic recording medium according to claim 6, wherein the underlayer is composed of two layers, and the layer on the first magnetic layer side has a higher concentration of the additive element in atomic% than the layer on the substrate side.   8. The magnetic recording according to claim 6, wherein the other underlayer is composed of two layers, and the layer on the first magnetic layer side has a higher concentration of the additive element in atomic% than the layer on the substrate side. Medium.   The magnetic recording medium according to any one of claims 3 to 9, further comprising another underlayer made of Cr or a Cr-based alloy immediately below the underlayer. Further comprising a seed layer between the substrate and the underlayer;
The magnetic recording medium according to claim 1, wherein the seed layer is made of a nonmagnetic amorphous metal or an alloy having a B2 structure. A substrate, an underlayer formed on the substrate, a first magnetic layer formed on the underlayer, a nonmagnetic coupling layer formed on the first magnetic layer, and the nonmagnetic coupling A second magnetic layer formed on the layer,
In the magnetic recording medium, the first magnetic layer and the second magnetic layer are exchange-coupled, and the magnetization of the first magnetic layer and the magnetization of the second magnetic layer are antiparallel to each other when no external magnetic field is applied. A manufacturing method comprising:
Forming the base layer on the substrate;
The method for producing a magnetic recording medium is characterized in that in the step of forming the underlayer, a Cr or Cr-based alloy having a bcc crystal structure is formed in an atmosphere gas containing nitrogen gas. Further comprising forming another underlayer between the underlayer and the first magnetic layer,
13. The magnetic layer according to claim 12, wherein in the step of forming the other underlayer, Cr or a Cr-based alloy having a bcc crystal structure is formed in an atmospheric gas containing 0.10% by volume or less of nitrogen gas. A method for manufacturing a recording medium.   14. The method of manufacturing a magnetic recording medium according to claim 13, wherein in the step of forming the underlayer, the film is formed in an atmospheric gas containing 0.01% by volume to 0.50% by volume of nitrogen gas. The Cr-based alloy having the bcc crystal structure is an alloy made of Cr and at least one additive element out of the group consisting of Mo, W, V, and Ti,
The underlayer and the other underlayer contain the same additive element,
15. The method for manufacturing a magnetic recording medium according to claim 13, wherein the other underlayer has a higher additive element concentration in atomic% than the underlayer.   In the other underlayer forming step, the film is formed in a rare gas atmosphere containing at least one selected from the group consisting of He, Ne, Ar, Kr, and Xe. A method for manufacturing a magnetic recording medium according to any one of the preceding claims. A magnetic recording medium according to any one of claims 1 to 11, or a magnetic recording medium formed by the manufacturing method according to any one of claims 12 to 16,
And a magnetic storage device.

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