JP2011119006A - Perpendicular magnetic recording medium which controls exchange interaction between ferromagnetic particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase magnetic recording density of a perpendicular magnetic recording medium and improve an S/N ratio. <P>SOLUTION: In a perpendicular magnetic recording medium, at least a soft magnetic base layer, an intermediate layer, a magnetic recording layer and a protection layer are laminated on a base board. The magnetic recording layer comprises two layers, a first magnetic recording layer 161 and a second magnetic recording layer 162, which are arranged in this order from the base board side. The first magnetic recording layer 161 and the second magnetic recording layer 162 are each composed of columnar ferromagnetic particles and grain boundary materials which surround the columnar ferromagnetic particles. The grain boundary material in the first magnetic recording layer 161 is different from the material for the grain boundary material in the second magnetic recording layer 162. The first magnetic recording layer 161 has negative exchange interaction to increase recording density and improve an S/N ratio in reproduction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultra-high density magnetic recording technique, and more particularly to a technique for increasing a recording density in a perpendicular magnetic recording medium and improving an S / N ratio during reproduction.

  Digitization is progressing rapidly in various fields, prompted by the development of information processing technology. In addition to personal computers and servers that have traditionally represented hardware, the need to store large amounts of digital data has also increased in home appliances, audio and medical equipment. In order to store these enormous amounts of data, magnetic disk devices (HDDs), which are the core of nonvolatile file systems, are required to have a larger capacity than ever before. Increasing the capacity of the magnetic disk device means increasing the surface recording density, that is, the bit density recorded on the medium.

  In HDDs currently in practical use, a recording medium composed of a ferromagnetic polycrystalline thin film is used for both in-plane recording and perpendicular recording. FIG. 1 is a schematic diagram of a recording state in a conventional magnetic recording medium. A conventional polycrystalline thin film is generally composed of magnetic particles 101 having high uniaxial magnetic anisotropy and a grain boundary material 102 mainly including a nonmagnetic material surrounding the magnetic particles 101.

  The basic operation for recording information is to apply a local magnetic field to an arbitrary position on the recording medium, and to reverse the magnetization polarity at an appropriate timing to change the magnetization at approximately 180 ° (magnetization transition 103). This magnetization transition 103 is made to correspond to 1 of digital information. Moreover, detecting the spatial change of the leakage magnetic field distribution in the vicinity of the magnetization transition 103 with an appropriate magnetic field sensor corresponds to data reproduction. Actually, input / output of information in the HDD is performed through processing such as encoding / decoding before and after the recording / reproducing operation.

  The recording density is the number of magnetization transitions 103 that can be written in a unit area, and the most important factor for increasing this is how sharply and smoothly each magnetization transition 103 can be formed. This magnetization transition 103 usually has a zigzag microstructure along the grain boundary, as shown in FIG. It can be said that the average width (transition width) of this zigzag represents the steepness of the magnetization transition.

  If this width is too wide, not only the recording interval does not increase because the bit interval cannot be reduced, but also a large noise is added to the reproduction signal, so that stable reading at a low bit error rate (BER) is impossible. There's a problem. Therefore, in the current magnetic recording system, the transition width is one of the biggest factors limiting the recording density. It has been found that this transition width is strongly influenced by the magnetic interaction acting between the grains as well as the size of the ferromagnetic crystal grains.

  FIG. 1 shows a schematic diagram of the magnetization state when the size of the unit for magnetization reversal is as large as several times the crystal grain size. In such a case, in order to reduce the unit of magnetization reversal and narrow the width of the magnetization transition 103, it is conceivable to directly reduce the magnetic particle 101.

  However, if the magnetic particles 101 are excessively miniaturized, the exchange interaction and its variation are increased, and the BER is increased by increasing the cluster size and its variation. Therefore, it is important to suppress the exchange interaction that is the cause of the cluster size larger than the crystal grain size.

  “Patent Document 1” is cited as a layer structure of a perpendicular magnetic recording medium. “Patent Document 1” describes that Ru having a hexagonal close-packed structure is used as an underlayer in order to reduce the magnetic interaction between magnetic particles constituting the magnetic layer.

JP-A-2005-7401

  In perpendicular magnetic recording, the unit of reversal of the magnetization of the medium at the time of recording is large (clustering) several times the crystal grain size of the magnetic recording layer, so the magnetization transition corresponding to the bit cannot be made sufficiently narrow, This has been an obstacle to higher recording density. The cause of this clustering is due to exchange interaction between ferromagnetic particles.

  FIG. 2 is a graph in which the horizontal axis represents the exchange magnetic field (Hexch), that is, the absolute value of the exchange interaction acting between the magnetic particles, and the vertical axis represents the frequency of the exchange interaction with the average size of the magnetic particles as a parameter. is there. In FIG. 1, the average diameter of the magnetic particles decreases in the order of A, B, and C. As shown in FIG. 2, when the average size of the magnetic particles is reduced, the variation in exchange interaction increases.

  In this way, if the crystal grain size is reduced in order to reduce the inversion unit, the exchange interaction magnetic field and its variation increase, and the recording performance deteriorates by increasing the cluster size or increasing the cluster size variation. Was. Therefore, it was necessary to reduce the exchange interaction itself in order to reduce the cluster size. However, it has been very difficult to reduce the exchange interaction using a single intergranular material.

  The magnetic recording layer of the perpendicular recording medium is divided into a plurality of layers having different characteristics. If negative exchange interaction is introduced into at least one of these layers, the exchange interaction can be minimized as a whole of the magnetic recording layer due to magnetic coupling between the layers. The negative exchange interaction is a force that attempts to direct the magnetization between the ferromagnetic particles antiparallel to each other.

Since the exchange interaction of the magnetic recording layer is minimized, the magnetization of each magnetic particle can behave as if it were independent. Therefore, the zigzag width of the magnetization transition can be made almost equal to the magnetic particle size. As described above, an ultra-high recording density exceeding 1 Tb / in ² was realized, and a small-sized, large-capacity magnetic disk device with a high transfer rate could be realized at low cost.

The schematic diagram which showed the reversal unit of the magnetization transition vicinity in perpendicular magnetic recording. It is the graph which represented the dispersion | variation in the exchange magnetic field by using the diameter of the magnetic particle as a parameter. It is a schematic diagram which shows the state of the magnetic particle in a magnetic recording layer. It is a cross-sectional schematic diagram of a second magnetic recording layer. It is a cross-sectional schematic diagram of a 1st magnetic recording layer. It is a graph which shows the distribution of the exchange magnetic field in a 1st magnetic recording layer and a 2nd magnetic recording layer. It is a graph which shows the relationship between exchange interaction energy and S / N ratio. It is a graph which shows the change of S / N ratio when the exchange interaction energy of a lower magnetic recording layer is changed when the exchange interaction energy of an upper magnetic recording layer is positive. 1 is a cross-sectional structure of a magnetic disk according to the present invention. 10 shows manufacturing conditions for manufacturing the magnetic disk of FIG. It is a schematic diagram showing the operation of the magnetic disk device.

  Hereinafter, specific magnetic recording media and magnetic disk devices to which the present invention is applied will be described in detail by way of examples.

  FIG. 3 is a schematic diagram showing only the magnetic recording layer 16 extracted from the magnetic disk (magnetic recording medium) according to the present invention. In FIG. 3, the magnetic recording layer 16 is formed of a first magnetic recording layer 161 and a second magnetic recording layer 162. The second magnetic recording layer 162 is located on the surface side of the magnetic disk, that is, on the magnetic head side. The magnetic particles 1611 of the first magnetic recording layer 161 and the magnetic particles 1621 of the second magnetic recording layer 162 are approximated as having a cylindrical structure. In the example of FIG. 3, the thickness of both the first magnetic recording layer 161 and the second magnetic recording layer 162 is, for example, about 10 nm. In addition, the magnetic particle in this specification is a ferromagnetic magnetic particle.

  Corresponding to the different diameters of the magnetic particles, the diameters of the columnar structures are different. The diameters of the magnetic particles of the first magnetic recording layer 161 and the second magnetic recording layer 162 are the same. That is, the diameter of the columnar structure is equal. In each layer, the diameter of the columnar structure is different corresponding to the variation in the diameter of the magnetic particles. Hereinafter, the cylindrical structure is referred to as a magnetic particle.

  In FIG. 3, a strong positive exchange interaction acts between the magnetic particles 1621 of the second magnetic recording layer 162 and the magnetic particles 1611 of the first magnetic recording layer 161. In FIG. 3, this state is represented as Hexch >> 0. Since the positive exchange interaction has the effect of directing the magnetic moment in the same direction, the magnetic particles of the first magnetic recording layer 161 and the magnetic particles of the second magnetic recording layer 162 are in the same direction. Has a magnetic moment.

  4 is a schematic cross-sectional view of the second magnetic recording layer 162 shown in FIG. 3, and FIG. 5 is a schematic cross-sectional view of the first magnetic recording layer 161. 4 and 5 have the same structure but different materials. In FIG. 4, the magnetic particles 1621 in the second magnetic recording layer 162 are formed of an alloy of 64Co-12Cr-14Pt-10B. Between the magnetic particles 1621 in the second magnetic recording layer 162, SiO 2 is filled as the grain boundary material 1622. In FIG. 4, the average diameter D of the magnetic particles is about 10 nm, and the size dispersion is 20 to 30%. The distance d between the magnetic particles and the magnetic particles is about 2 to 3 nm.

  In FIG. 5, the magnetic particles 1611 in the first magnetic recording layer 161 are made of an alloy of 61Co-21Cr-18Pt-6molSiO2. Between the magnetic particles 1611 in the first magnetic recording layer 161, Ru is filled as the grain boundary material 1612. Note that the grain boundary material 1612 may be filled with Cr, Ir, Rh, or their oxide instead of Ru. In FIG. 5, the average diameter D of the magnetic particles is about 10 nm, and the size dispersion is 20 to 30%. The distance d between the magnetic particles and the magnetic particles is about 2 to 3 nm, which is equivalent to that in FIG.

  Since the magnetic particles 1611 in the second magnetic recording layer 161 and the magnetic particles 1621 in the second magnetic recording layer 162 need to have the same magnetic moment, the magnetic particles 1611 in the first magnetic recording layer 161 and the second magnetic recording layer 162 have the same magnetic moment. It is necessary that a strong positive exchange interaction is working with the magnetic particle 1621. However, if a strong positive exchange interaction is acting between the first magnetic recording layer 161 and the second magnetic recording layer 162, the first magnetic layer can be obtained by using the conventionally used SiO 2 as the grain boundary material. Positive exchange interaction energy acts between adjacent magnetic particles in the recording layer 161 or the second magnetic recording layer 162. This state is represented as J> 0 in FIGS.

  When positive exchange interaction energy acts between adjacent magnetic particles in the same layer, the size and variation of the magnetic recording cluster are increased. Therefore, the width of the magnetization transition is increased, which becomes an obstacle to increase in recording density. That is, even if the size of the magnetic particles is reduced in order to increase the recording density, the size of the magnetic cluster cannot be reduced and the recording density cannot be increased.

  In the present invention, in order to cope with this, the grain boundary materials in the first magnetic recording layer 161 and the second magnetic recording layer 162 are different. That is, as shown in FIG. 4, in the upper second magnetic recording layer 162, the grain boundary material 1622 between the magnetic particles is made of SiO2 as in the prior art, whereas in the lower first magnetic recording layer 161, The grain boundary material 1612 between the magnetic particles is Ru.

  In the second magnetic recording layer 162, between adjacent magnetic particles, SiO2 is used as the grain boundary material, so that positive exchange interaction energy works. On the other hand, in the first magnetic recording layer 161, since Ru is used as a grain boundary material, negative exchange interaction energy works between adjacent magnetic particles. This state is represented as J <0 in FIGS. Even if Ir, Cr, Rh, or an oxide thereof is used instead of Ru, negative exchange interaction energy can work between adjacent magnetic particles 1611 in the same magnetic recording layer 161.

  On the other hand, the magnetic particles in the first magnetic recording layer 161 and the second magnetic recording layer 162 have the same continuous columnar structure. With such a configuration, the exchange interaction energy is canceled and becomes zero between the magnetic particles in the second magnetic recording layer 162 and the first magnetic recording layer 161. This is shown in FIG. In FIG. 6, the horizontal axis is the exchange magnetic field (Hexch), and the vertical axis is the frequency of exchange interaction.

  In FIG. 6, when the exchange magnetic field is positive, that is, when the exchange magnetic field is positive, it represents the frequency of exchange interaction in the second magnetic recording layer 162, and when the exchange magnetic field is negative, that is, when the exchange magnetic field is negative, in the first magnetic recording layer 161. It represents the frequency of exchange interactions. Since the magnetic particles in the second magnetic recording layer 162 and the magnetic particles in the first magnetic recording layer 161 have the same columnar structure, the frequency curve with respect to the exchange magnetic field has a mirror-symmetrical relationship across the y axis. ing. This indicates that in the first magnetic recording layer 161 and the second magnetic recording layer 162, the exchange interaction between adjacent magnetic particles can be made zero.

  Thus, the size of the magnetic cluster can be reduced by reducing the exchange interaction between adjacent magnetic particles to zero. Further, since the transition width can be reduced, the recording density can be increased and the noise with respect to the reproduction signal can be reduced.

In FIG. 7, the horizontal axis represents the exchange interaction energy J, and the vertical axis represents the SN ratio of the reproduction signal. That is, FIG. 7 is a simulation of how the S / N ratio of the reproduction signal varies depending on the value of the exchange interaction energy J between magnetic particles in the same layer. The unit of the exchange interaction energy is ^10- 13 J / m.

  When the recording layer is divided into the first magnetic recording layer 161 and the second magnetic recording layer 162, the horizontal axis in FIG. 7 represents the sum of the magnetic particles in the first magnetic recording layer 161 and the magnetic particles in the second magnetic recording layer 162. Is the exchange interaction energy. As the total exchange interaction energy increases to a positive value, the S / N ratio decreases. In addition, the SN ratio decreases as the sum of exchange interaction energies increases toward the negative side. The SN ratio is the highest when the total exchange interaction energy is zero. That is, the S / N ratio decreases as the absolute value of the exchange interaction energy increases.

  FIG. 8 shows the exchange interaction of the lower magnetic layer 161, that is, the first magnetic recording layer 161 when the value of the exchange interaction energy of the second magnetic recording layer 162 is positive. It is the graph which evaluated how S / N ratio changed when energy was changed.

  In FIG. 8, the horizontal axis represents the exchange interaction energy of the first magnetic recording layer 161, and the vertical axis represents the SN ratio of the reproduction signal. As can be seen from FIG. 8, the S / N ratio decreases as the exchange interaction energy of the first magnetic recording layer 161 increases to the positive side. This is because since the exchange interaction energy of the second magnetic recording layer 162 is positive, the absolute value of the total exchange interaction energy of the first magnetic recording layer 161 and the second magnetic recording layer 162 becomes large.

On the other hand, in FIG. 8, when the exchange interaction energy of the first magnetic recording layer 161 is increased to the negative side, the SN ratio gradually increases, and the exchange interaction energy becomes −5 × 10 ⁻¹³ J / m. Thus, the S / N ratio becomes maximum. This is because the exchange interaction energy of the second magnetic recording layer 162 on the surface side of the magnetic disk is positive, so that the value of the exchange interaction energy of the lower first magnetic recording layer 161 is −5 × 10 ⁻¹³ J / m. This is because the exchange interaction energy between the first magnetic recording layer 161 and the second magnetic recording layer 162 is canceled and becomes zero. When the exchange interaction energy of the first magnetic recording layer 161 is further increased to the negative side, the S / N ratio decreases. That is, when the value of the first magnetic recording layer 161 is further increased to the negative side, the total absolute value of the exchange interaction energy is increased, so that the SN ratio is decreased.

  As described above, according to the present invention, the grain boundary material 1622 in the second magnetic recording layer 162 and the grain boundary material 1612 in the first magnetic recording layer 161 are different, and the sign of the exchange interaction energy in the first magnetic recording layer 161 is changed. By reversing the sign of the exchange interaction energy in the second magnetic recording layer 162, the SN ratio can be improved.

  Specifically, the exchange interaction energy of the second magnetic recording layer 162 is made positive by setting the grain boundary material 1622 in the second magnetic recording layer 162 to SiO2. On the other hand, by setting the grain boundary material 1612 in the first magnetic recording layer 161 to Ru, the exchange interaction energy of the first magnetic recording layer 161 is made negative. By controlling the film thickness and the like of the first magnetic recording layer 161 and the second magnetic recording layer 162, the optimum conditions, that is, the total exchange interaction energy can be made zero. Even if Cr, Ti, Ir, or an oxide thereof is used as the grain boundary material of the first magnetic recording layer 161, the value of the exchange interaction energy of the first magnetic recording layer 161 can be made negative.

  FIG. 9 is an example of a detailed cross-sectional structure of the magnetic disk according to the present invention, and the table shown in FIG. 10 shows manufacturing conditions for manufacturing the magnetic disk of FIG. In this embodiment, all the layers of the magnetic disk shown in FIG. 9 are formed by sputtering.

  In FIG. 9, the substrate 11 is made of glass or an Al substrate plated with a NiP alloy. On the substrate 11, an adhesion layer 12 for improving the adhesion between each layer of the recording medium and the substrate is formed. As shown in FIG. 10, the adhesion layer 12 is formed by sputtering a 65Ni35Ta target in an argon atmosphere of 1 Pa. The thickness of the adhesion layer is 10 nm.

  As shown in FIG. 9, a soft magnetic underlayer 13 is formed on the adhesion layer 12. The soft magnetic underlayer 13 has a role of increasing the recording density in the magnetic recording layer 16 by attracting magnetic flux from the write head when writing a magnetic signal to the recording layer. The soft magnetic underlayer 13 is formed of three layers, which are a first soft magnetic layer 131, a nonmagnetic layer 132, and a second soft magnetic layer 133 from the bottom.

  As shown in FIG. 10, the first soft magnetic layer 131 is formed by sputtering a 51Fe-34-Co-10Ta-5Zr target in an atmosphere with an Ar gas pressure of 0.5 Pa. The thickness of the first soft magnetic layer 131 is 15 nm.

  On the first soft magnetic layer 131, as the nonmagnetic layer 132, Ru is formed to a thickness of 0.4 nm by sputtering under an Ar gas pressure of 1 Pa. A second soft magnetic layer 133 is formed on the nonmagnetic layer 132 by sputtering a 51Fe-34-Co-10Ta-5Zr target in an atmosphere with an Ar gas pressure of 0.5 Pa. The thickness of the second soft magnetic layer 133 is 5.5 nm. The second soft magnetic layer 133 has the same components as the first soft magnetic 131 but has a different thickness.

  By making the soft magnetic underlayer 13 three layers instead of one, the magnetization state of the soft magnetic underlayer 13 is stabilized. That is, the Ru layer 132 which is a nonmagnetic layer is disposed between the first soft magnetic layer 131 and the second soft magnetic layer 133, and the exchange mutual between the first soft magnetic layer 131 and the second soft magnetic 133 is performed. By making the action energy negative, the magnetization moments of the first soft magnetic layer 131 and the second soft magnetic layer 133 are reversed, thereby stabilizing the magnetization state of the soft magnetic underlayer 13.

  As shown in FIG. 9, a seed layer 14 is formed on the soft magnetic underlayer 13. The seed layer 14 has a role of improving crystal orientation in the magnetic recording layer 16. This can increase the magnetic anisotropy of the recording layer. The seed layer 14 is formed of two layers.

  As shown in FIG. 10, the first seed layer 141 is formed by sputtering an 85.5Co-9.5Fe-5Ta target in an atmosphere with an Ar gas pressure of 0.5 Pa. The thickness of the first seed layer 141 is 7 nm. The second seed layer 142 is formed by sputtering 85.5Co-9.5Fe-5Ta on a 94Ni-6W target in an atmosphere with an Ar gas pressure of 1 Pa. The thickness of the second seed layer 142 is 3 nm.

  As shown in FIG. 9, the intermediate layer 15 is formed on the seed layer 14. The intermediate layer 15 has a role as a buffer layer between the soft magnetic underlayer 13 and the magnetic recording layer 16 and a role of controlling the particle size of the magnetic recording layer 16. For the intermediate layer 15, Ru which is a nonmagnetic material is used. As shown in FIG. 10, the intermediate layer 15 is formed to a thickness of 4 nm by sputtering a Ru target in an atmosphere with an Ar gas pressure of 1 Pa. When the intermediate layer is formed thick according to specifications, the intermediate layer is formed to a thickness of 8 nm by sputtering a Ru target in an atmosphere with an Ar gas pressure of 5 Pa. Ti may be used as the material of the intermediate layer 15.

  As shown in FIG. 9, the magnetic recording layer 16 is formed on the intermediate layer 15, and the magnetic recording layer 16 has a two-layer structure. The first magnetic recording layer 161 and the second magnetic recording layer 162 are sequentially arranged from the bottom. It has become. The thicknesses of the first magnetic recording layer 161 and the second magnetic recording layer 162 in FIG. 9 are different from those in FIG. The first magnetic recording layer 161 is made of a grain boundary material filled between magnetic particles. As shown in FIG. 10, the magnetic particles of the first magnetic recording layer 161 are formed by sputtering a target of 61Co-21Cr-18Pt-6molSiO2 in an atmosphere with an Ar gas pressure of 4.5 Pa.

  On the other hand, the grain boundary material in the first magnetic recording layer 161 is formed by sputtering Ru in Ar gas in the same atmosphere. In the first magnetic recording layer 161, first, nuclei of magnetic particles composed of 61Co-21Cr-18Pt-6molSiO2 grow, and a grain boundary material of Ru grows so as to surround the nuclei. As a result, a structure is formed in which the grain boundary material of Ru is filled between the magnetic particles. The thickness of the first magnetic recording layer 161 is 13 nm. Since the grain boundary material of the first magnetic recording layer 161 is Ru, the exchange interaction energy J takes a negative value.

  As shown in FIG. 9, the second magnetic recording layer 162 is formed on the first magnetic recording layer 161. The second magnetic recording layer 162 is also made of a grain boundary material filled between the magnetic particles. As shown in FIG. 10, the magnetic particles of the second magnetic recording layer 162 are formed by sputtering a 64-Co-12Cr-14Pt-10B target in an atmosphere with an Ar gas pressure of 0.6 Pa.

  On the other hand, the grain boundary material in the second magnetic recording layer 162 is formed by sputtering SiO 2 in Ar gas in the same atmosphere. In the second magnetic recording layer 162, first, nuclei of magnetic particles composed of 64Co-12Cr-14Pt-10B are grown, and a grain boundary material made of SiO2 is grown so as to surround the nuclei. As a result, a structure is formed in which the grain boundary material made of SiO2 is filled between the magnetic particles. The thickness of the second magnetic recording layer 162 is 3 nm. Since the grain boundary material of the second magnetic recording layer 162 is SiO2, the exchange interaction energy J takes a positive value.

  As shown in FIG. 9, a protective layer for protecting the magnetic recording layer 16 is formed on the magnetic recording layer 16. As shown in FIG. 10, the protective layer is formed by sputtering Carbon in an atmosphere with an Ar gas pressure of 0.6 Pa. The thickness of the protective film is 3 nm.

  In the magnetic disk thus formed, the exchange interaction energy of the first magnetic recording layer 161 and the exchange interaction energy of the second magnetic recording layer 162 have opposite signs. The absolute value of can be reduced, and the size of the magnetic cluster can be kept small. As a result, the transition width can be kept small, the recording density can be increased, and the SN ratio during reproduction can be improved.

  In the above description, the magnetic recording layer 16 is formed of two layers, but the present invention is also applied to the case where the magnetic recording layer 16 is formed of a plurality of magnetic recording layers 16 of three or more layers. I can do it. When the magnetic recording layer 16 is formed of three or more magnetic recording layers 16, the effect of the present invention can be obtained by setting the exchange interaction energy of at least one magnetic recording layer 16 to a negative exchange interaction energy. Can be obtained. That is, the effect of the present invention can be obtained by arranging the layers so as to reduce the absolute value of the total exchange interaction energy of each layer.

  FIG. 11 is a conceptual diagram showing the relationship between the components of the magnetic disk device. The slider on which the magnetic head 31 is mounted is supported by a suspension arm 32 and is positioned on the disk-shaped magnetic recording medium 34 by an actuator 33 to read / write information at a desired location. The rotation of the magnetic recording medium 34 is controlled by a spindle motor 35, and a signal (servo signal) indicating the position is recorded in advance in a servo area above the magnetic recording medium 34, and the servo signal read by the head is processed by the mechanism control system 45. In addition, closed loop control is performed by feeding back to the actuator 33.

  User data input through the external interface 44 is encoded and shaped by the controller 43 and the data encoding / decoding system 42 by a method suitable for the magnetic recording system, and converted into a recording current waveform by the recording / reproducing amplifier 41. Bits are written in the user data area of the magnetic recording medium 34 by exciting the recording element of the magnetic head 31. On the contrary, the magnetic field leaked from the written bit is converted into an electrical signal by sensing by the reproducing element of the magnetic head 31, and the recording / reproducing amplifier 41 and the data encoding / decoding system 42 are suitable for the magnetic recording system. User data is reproduced through the waveform shaping / decoding process.

  By using the magnetic disk according to the present invention in the magnetic disk apparatus shown in FIG. 11, a magnetic disk having a high recording density and a high SN ratio can be realized.

DESCRIPTION OF SYMBOLS 11 ... Substrate, 12 ... Adhesion layer, 13 ... Soft magnetic underlayer, 14 ... Seed layer, 15 ... Intermediate layer, 16 ... Recording layer, 17 ... Protective layer, 18 ... Nonmagnetic layer, 131 ... First soft magnetic layer, 132: Nonmagnetic layer, 133: Second soft magnetic layer, 141: First seed layer, 142: Second seed layer, 143: Third seed layer, 31: Magnetic head, 33: Actuator, 34: Magnetic recording medium, 35 ... spindle motor, 41 ... recording / reproducing amplifier, 42 ... data encoding / decoding system, 43 ... controller, 44 ... external interface, 45 ... mechanism control system, 101 ... magnetic particles, 102 ... grain boundary material, 103 ... magnetization transition.

Claims (7)

  A perpendicular magnetic recording medium in which at least a soft magnetic underlayer, an intermediate layer, a magnetic recording layer, and a protective layer are laminated on a substrate, wherein the magnetic recording layer is a first magnetic recording layer and a second magnetic recording layer from the substrate side. The first magnetic recording layer and the second magnetic recording layer are each composed of aggregates of columnar ferromagnetic particles, and the grain boundaries surrounding the ferromagnetic particles in the first magnetic recording layer A perpendicular magnetic recording medium, wherein a material of the material and a grain boundary material surrounding the ferromagnetic particles in the second magnetic recording layer are different.   2. The first magnetic recording layer or the second magnetic recording layer has a negative exchange interaction that attempts to direct magnetization between the ferromagnetic particles antiparallel to each other. Perpendicular magnetic recording media.   The at least one layer of the first magnetic recording layer or the second magnetic recording layer contains Ru, Cr, Ti, Ir, or an oxide of these metals as the grain boundary material. Perpendicular magnetic recording medium.   The first magnetic recording layer includes Ru, Cr, Ti, Ir, or an oxide of these metals as the grain boundary material, and the second magnetic recording layer includes SiO 2 as the grain boundary material. The perpendicular magnetic recording medium according to claim 1.   The perpendicular magnetic recording medium according to claim 1, wherein the first magnetic recording layer has a negative exchange interaction, and the second magnetic recording layer has a positive exchange interaction.   A perpendicular magnetic recording medium in which at least a soft magnetic underlayer, an intermediate layer, a magnetic recording layer, and a protective layer are laminated on a substrate, wherein the magnetic recording layer is a first magnetic recording layer and a second magnetic recording layer from the substrate side. Each of the plurality of magnetic recording layers is composed of an aggregate of columnar ferromagnetic particles, and at least one of the plurality of magnetic recording layers is the ferromagnetic particle. The perpendicular magnetic recording medium is characterized in that the material of the grain boundary material surrounding the magnetic material is different from the grain boundary material surrounding the ferromagnetic particles in the other magnetic recording layer.   A perpendicular magnetic recording medium in which at least a soft magnetic underlayer, an intermediate layer, a magnetic recording layer, and a protective layer are laminated on a substrate, wherein the magnetic recording layer is a first magnetic recording layer and a second magnetic recording layer from the substrate side. Each of the plurality of magnetic recording layers is made of columnar ferromagnetic particles and a grain boundary material surrounding the ferromagnetic particles, and at least of the plurality of magnetic recording layers. The perpendicular magnetic recording medium according to claim 1, wherein the first layer has a negative exchange interaction for directing magnetization between the ferromagnetic particles antiparallel to each other.

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