JP4220508B2 - Perpendicular magnetic recording medium and magnetic recording / reproducing apparatus using the same - Google Patents

Description

  The present invention relates to a perpendicular magnetic recording type magnetic recording / reproducing apparatus and a perpendicular magnetic recording medium used therefor.

  Conventionally, in a perpendicular double-layer medium in which a perpendicular magnetic recording layer is laminated on a soft magnetic layer having a high magnetic permeability, the soft magnetic layer passes a recording magnetic field from a magnetic head for magnetizing the perpendicular magnetic recording layer in the horizontal direction. It plays a part of the function of the magnetic head that recirculates to the magnetic head side, and plays the role of improving the recording and reproducing efficiency. However, on the other hand, the soft magnetic layer tends to form a magnetic domain in order to reduce magnetostatic energy, and at this time, a domain wall is formed at the boundary between the magnetic domain and the magnetic domain. It is known that spike-like noise occurs in the region where the domain wall exists. In order to suppress this spike noise, the formation of the domain wall of the soft magnetic layer may be suppressed. As a method for this purpose, many media have been proposed in the past in which a hard magnetic layer is provided under the soft magnetic layer and the easy magnetization direction of the soft magnetic layer is fixed in the radial direction (see, for example, Patent Document 1).

  However, since the soft magnetic layer is directly formed on the hard magnetic layer in the above-described medium, the exchange coupling interaction acts between them more strongly than necessary. The soft magnetic layer is characterized in that the magnetization direction changes greatly even when a weak external magnetic field of, for example, about 7900 A / m is applied.

  At this time, the stronger the coupling with the soft magnetic layer, the more easily the hard magnetic layer is affected, and the phenomenon that the magnetization direction of the hard magnetic layer, that is, the easy axis of magnetization, deviates from the radial direction, so-called demagnetization occurs. was there. In fact, in a magnetic recording / reproducing apparatus (HDD), a voice coil motor (VCM) using a permanent magnet for driving an arm is in a positional relationship close to a magnetic disk. The leakage magnetic flux generated from the VCM has a magnitude of about 7900 A / m even near the outer periphery of the magnetic disk. For this reason, when the above-described medium is used in an HDD, a demagnetization may occur, which is a particularly serious problem.

Although it is convenient to use a hard magnetic layer in terms of controlling the direction of the easy axis of the soft magnetic layer, the hard magnetic layer is basically the same as the in-plane magnetic recording medium, and is the source of medium noise. Become. Although the thickness of the soft magnetic layer is preferably thin from the viewpoint of dust generation during production and the cost, etc., the soft magnetic layer becomes thinner and the closer the distance between the hard magnetic layer and the magnetic head, the more Noise increases. One means for reducing noise from the hard magnetic layer is to make it thinner. Decreasing the thickness of the hard magnetic layer is advantageous from the viewpoint of improving the film forming process and cost, but if exchange coupling is working strongly, it is likely to cause demagnetization. There was a problem.
JP-A-5-258274

  The present invention has been made in view of the above prior art, and an object of the present invention is to provide a perpendicular magnetic recording medium in which occurrence of demagnetization due to an external magnetic field is suppressed and medium noise is reduced.

According to the present invention, in the perpendicular magnetic recording medium in which an in-plane hard magnetic layer, an in-plane soft magnetic layer, and a perpendicular magnetic recording layer are sequentially laminated on a substrate, the in- plane hard magnetic layer has a thickness of 50 nm or less. The in- plane hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled to each other than when the in-plane soft magnetic layer is formed directly on the uniform in-plane hard magnetic layer. A perpendicular magnetic recording medium is provided.

  The perpendicular magnetic recording medium of the present invention is roughly classified into the following six viewpoints.

  A perpendicular magnetic recording medium according to a first aspect of the present invention is provided on a substrate, an in-plane hard magnetic layer having a thickness of 50 nm or less formed on the substrate, and the in-plane hard magnetic layer. A magnetic layer having a saturation magnetization smaller than that of the inner hard magnetic layer, an in-plane soft magnetic layer provided on the magnetic layer, and a magnetic recording layer are provided.

  A perpendicular magnetic recording medium according to a second aspect of the present invention includes a substrate, an in-plane hard magnetic layer formed on the substrate and having a thickness of 50 nm or less, and an in-plane hard magnetic layer provided on the in-plane hard magnetic layer. And a non-magnetic layer having a thickness of 5 nm or less, an in-plane soft magnetic layer provided on the non-magnetic layer, and a magnetic recording layer provided on the in-plane soft magnetic layer.

  A perpendicular magnetic recording medium according to a third aspect of the present invention is a substrate, an in-plane hard magnetic layer having a thickness of 50 nm or less formed on the substrate, provided on the in-plane hard magnetic layer, and cobalt. A nonmagnetic layer mainly contained, an in-plane soft magnetic layer provided on the nonmagnetic layer, and a perpendicular magnetic recording layer provided on the inplane soft magnetic layer are provided.

  A perpendicular magnetic recording medium according to a fourth aspect of the present invention is a substrate, an in-plane hard magnetic layer formed on the substrate, having a thickness of 50 nm or less, provided on the in-plane hard magnetic layer, and containing ruthenium. A nonmagnetic layer mainly contained, an in-plane soft magnetic layer provided on the nonmagnetic layer, and a perpendicular magnetic recording layer provided on the inplane soft magnetic layer are provided.

  The perpendicular magnetic recording medium according to the fifth aspect of the present invention is a substrate, an in-plane hard magnetic layer formed on the substrate and having a thickness of 50 nm or less, and this surface provided on the in-plane hard magnetic layer. It comprises an oxide layer of an inner hard magnetic layer, an in-plane soft magnetic layer provided on the oxide layer, and a perpendicular magnetic recording layer provided on the in-plane soft magnetic layer.

  A magnetic recording / reproducing apparatus according to a sixth aspect of the present invention includes a magnetic recording medium according to any one of the first to fifth aspects, a driving unit that supports and rotationally drives the perpendicular magnetic recording medium, An element for recording information on the perpendicular magnetic recording medium, a magnetic head having an element for reproducing recorded information, and the magnetic head movable relative to the perpendicular magnetic recording medium And a supported carriage assembly.

  According to the present invention, it is possible to obtain a perpendicular magnetic recording medium in which occurrence of demagnetization due to an external magnetic field is suppressed and medium noise is reduced.

  In the perpendicular magnetic recording medium in which an in-plane hard magnetic layer, an in-plane soft magnetic layer, and a perpendicular magnetic recording layer are stacked, the present inventors suppress the occurrence of demagnetization due to the external magnetic field and reduce the medium noise. In order to achieve this, we conducted intensive research.

  As a result, the present inventors have formed an in-plane soft magnetic layer directly on a uniform in-plane hard magnetic layer in order to suppress the occurrence of demagnetization due to an external magnetic field without increasing medium noise. In particular, the inventors have focused on obtaining a medium in which the in-plane hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled, and have reached the present invention.

  For this purpose, in the magnetic characteristics of the composite layer portion of the in-plane hard magnetic layer and the in-plane soft magnetic layer, the substantial coercive force of the in-plane hard magnetic layer is directly applied to the in-plane hard magnetic layer on the surface. It is desirable that it be larger than when the inner soft magnetic layer is formed. Thereby, the exchange coupling between the hard magnetic layer and the soft magnetic layer can be moderately weakened, and the occurrence of demagnetization can be further suppressed.

  Furthermore, it is desirable that the substantial coercive force of the in-plane hard magnetic layer in the composite layer portion is smaller than the coercivity of the in-plane hard magnetic layer alone. Thereby, the magnetization direction of the soft magnetic layer can be more strongly fixed, and the occurrence of demagnetization can be further suppressed.

  In the present invention, the exchange coupling between the hard magnetic layer and the soft magnetic layer refers to an action in which the magnetization of the hard magnetic layer and the magnetization of the soft magnetic layer are exchange coupled.

  According to a first aspect of the present invention, a substrate, an in-plane hard magnetic layer formed on the substrate, an in-plane soft magnetic layer formed on the in-plane hard magnetic layer, and an in-plane soft magnetic layer are formed. Provided is a magnetic recording medium having a magnetic recording layer having a magnetic layer having a saturation magnetization smaller than that of the in-plane hard magnetic layer between the in-plane hard magnetic layer and the in-plane hard magnetic layer. Is done.

  In the invention according to the first aspect, by providing a magnetic layer having a saturation magnetization smaller than that of the in-plane hard magnetic layer, the exchange coupling between the hard magnetic layer and the soft magnetic layer is adjusted appropriately without being weakened, and the medium noise is reduced. Can be prevented from increasing due to an external magnetic field. Further, by reducing the thickness of the hard magnetic layer by that amount, medium noise can be reduced.

  According to the second to fourth aspects of the present invention, the in-plane hard magnetic layer formed on the substrate, the in-plane soft magnetic layer formed on the in-plane hard magnetic layer, and the in-plane soft magnetic layer are formed. In a magnetic recording medium having a magnetic recording layer formed on a magnetic layer, a magnetic recording medium is provided in which a predetermined nonmagnetic layer is provided between an in-plane hard magnetic layer and an in-plane soft magnetic layer.

  In the invention according to the second aspect, the nonmagnetic layer mainly contains cobalt.

  In the invention according to the third aspect, the nonmagnetic layer mainly contains ruthenium.

  In the invention according to the fourth aspect, the nonmagnetic layer has a thickness of less than 0.5 nm.

  In the invention according to the second to fourth aspects, by providing a predetermined nonmagnetic layer, the exchange coupling between the hard magnetic layer and the soft magnetic layer is moderately weakened, and an external magnetic field is generated without increasing the medium noise. It is possible to suppress demagnetization.

  Furthermore, according to the fifth aspect of the present invention, a substrate, an in-plane hard magnetic layer formed on the substrate and having a thickness of 50 nm or less, an in-plane soft magnetic layer formed on the in-plane hard magnetic layer, And a magnetic recording medium having a magnetic recording layer formed on the in-plane soft magnetic layer, wherein an in-plane hard magnetic layer oxide layer is provided between the in-plane hard magnetic layer and the in-plane soft magnetic layer Is provided.

  In the invention according to the fifth aspect, by providing the oxide layer, it is possible to moderately weaken the exchange coupling between the hard magnetic layer and the soft magnetic layer, and to suppress demagnetization due to an external magnetic field without increasing the medium noise. I can do it.

  FIG. 1 is a diagram showing an example of the configuration of the magnetic recording medium of the present invention.

  As shown in the figure, the magnetic recording medium of the present invention has a configuration in which an in-plane hard magnetic layer 2, an intermediate layer 3, an in-plane soft magnetic layer 4, and a magnetic recording layer 5 are provided in this order on a substrate 1. As the intermediate layer 3, a magnetic layer having a saturation magnetization smaller than that of the in-plane hard magnetic layer 4, a nonmagnetic layer, or an oxide layer of the in-plane hard magnetic layer 4 is provided.

  The nonmagnetic layer preferably mainly contains at least one of cobalt, ruthenium, vanadium, chromium, copper, and molybdenum.

  When the main component is cobalt, the thickness of the nonmagnetic layer is preferably 1 nm to 5 nm. Also, cobalt can be used in combination with ruthenium or chromium.

  When the main component is ruthenium, the thickness of the nonmagnetic layer can be 0.5 nm to 0.9 nm.

  When vanadium, chromium, copper, and molybdenum are main components, the thickness of the nonmagnetic layer is less than 0.5 nm. At this time, considering the manufacturing process of the medium, if the layer thickness per layer is too thin, it becomes difficult to control the layer thickness and maintain uniformity over the entire surface of the disk. It is preferable to have a thickness of For these reasons, the preferred thickness of the nonmagnetic layer is not less than 0.3 nm and less than 0.5 nm.

  As a method for increasing the thickness of the intermediate layer while keeping the exchange coupling at an appropriate size, it is conceivable that the intermediate layer has a certain degree of magnetism. At this time, the magnitude of the saturation magnetization is preferably smaller than the hard magnetic layer in consideration of inserting an intermediate layer for the purpose of weakening the coupling.

  The saturation magnetization of the magnetic layer is preferably ¼ or less of the saturation magnetization of in-plane hard magnetism.

  For a magnetic layer having a saturation magnetization smaller than that of the hard magnetic layer provided between the hard magnetic layer and the soft magnetic layer, 3d such as Fe, Co, or Ni is used from the viewpoint of easy mixing with other metals and crystal structure. It is preferable to add a magnetic metal. For example, when a CoCrPt alloy is used for the hard magnetic layer and CoZrNb is used for the soft magnetic layer, Co is contained in both layers. RuCo or CoCr having the same hexagonal close-packed structure as the layer is desirable. Here, since CoZrNb is amorphous, the crystallinity of the soft magnetic layer is not taken into consideration. However, when the soft magnetic layer is crystalline, Fe of a body-centered cubic structure or a face-centered cubic structure is considered in consideration of epitaxial growth. It is considered good to use Ni as needed.

  The thickness of the in-plane hard magnetic layer is preferably 50 nm or less, more preferably 5 nm to 50 nm, and still more preferably 10 nm to 40 nm. When the thickness of the in-plane hard magnetic layer is 50 nm or less, the medium noise can be further reduced. If the thickness is less than 5 nm, sufficient magnetic properties and magnetization effects tend not to be obtained. If the thickness exceeds 50 nm, sufficient magnetization can be achieved even when a soft magnetic layer is formed directly on the hard magnetic layer without using a nonmagnetic layer. Magnetic effect can be obtained and medium noise tends to increase.

  On the other hand, the thickness of the in-plane soft magnetic layer is preferably 20 nm or more, more preferably 20 nm to 500 nm, and still more preferably 50 nm to 400 nm. If the thickness of the in-plane soft magnetic layer exceeds 500 nm, dust is likely to be generated during sputtering, and irregularities on the surface of the magnetic recording medium increase, making it difficult to reduce the flying height of the head. It is possible to further suppress demagnetization. When the thickness is less than 20 nm, the coercive force of the portion corresponding to the soft magnetic layer increases, and there is a tendency that sufficient soft magnetic properties are not exhibited.

  As the in-plane hard magnetic layer, for example, an alloy mainly containing Co, Cr, and Pt, or a rare earth magnetic alloy such as SmCo can be used.

  The in-plane hard magnetic layer may further include at least one selected from the group consisting of palladium, ruthenium, and rhodium.

  Examples of the in-plane soft magnetic layer include CoZrNb, FeTaC, FeZrN, FeSi alloy, FeAl alloy, FeNi alloy such as permalloy, FeCo alloy such as permendur, FeCoNi alloy such as permin bar, NiCo alloy, Sendust, MnZn ferrite , NiZn-based ferrite, MgZn-based ferrite, MgMn-based ferrite, FeAlGa, FeCuNbSiB, FeGaGe, FeGeSi, FeNiPb, FeRuGaSi, FeSiB, FeSiC, FeZrB, FeZrBCu, CoFeSiB, CoTi, CoZrTa, etc. Can be used.

  As the perpendicular magnetic recording layer, for example, as the perpendicular magnetic recording layer, in addition to an alloy containing Co, Cr and Pt as main components similar to the in-plane magnetic recording medium, for example, a CoCr alloy, a CoPt alloy, CoPtO, CoPtCrO, CoPtB, CoPtCrB, and a multilayer structure of Co and an alloy mainly composed of at least one selected from the group consisting of Pt, Pd, Rh, and Ru, and CoCr / PtCr with Cr, B, and O added thereto, CoB / PdB, CoO / RhO, etc. can be used.

  In the present invention, a nonmagnetic underlayer can be provided between the soft magnetic layer and the perpendicular magnetic recording layer.Since the crystallinity of the soft magnetic layer surface differs depending on the material, the magnetization of the perpendicular magnetic recording layer In order to control the crystal orientation so that the axial direction becomes the vertical direction, it is preferable to provide a nonmagnetic underlayer. By providing this nonmagnetic underlayer, it is necessary to improve the crystal grain size, medium noise, recording resolution, and the like.

  Further, when a material containing at least one selected from Co, Cr and Pt is used for the magnetic recording layer, this nonmagnetic underlayer is similarly coated with Co, Cr and Pt from the viewpoint of lattice mismatch. It is desirable to use a material having a composition that becomes non-magnetic using. On the other hand, in addition to using Pt alone as the nonmagnetic underlayer, good magnetic characteristics and recording / reproducing characteristics can be obtained by using Pd, Rh, and Ru. Therefore, between the soft magnetic layer and the perpendicular magnetic recording layer, By using an alloy mainly composed of at least one selected from the group consisting of Co, Cr, Pt, Pd, Rh, and Ru, further improvement in magnetic characteristics and recording / reproducing characteristics can be expected.

  Further, before forming the nonmagnetic underlayer, for example, B, C, Al, Si, P, Ti, Zr, Hf, Cr, V, Nb, Ta, Ru, Rd, Pd, Pt, Cu, Ag, Au, and NiAl, NiTa in which these are combined with magnetic metals such as Fe, Co, and Ni, and oxides and nitrides thereof can be used.

  As the non-magnetic substrate, a glass substrate, an Al-based alloy substrate, a Si single crystal substrate having an oxidized surface, or a substrate having a surface plated with NiP or the like can be used.

  Further, although only the sputtering method is taken up as a film forming method for each layer, a similar effect can be obtained by a vacuum evaporation method or the like.

  According to a sixth aspect of the present invention, the perpendicular magnetic recording medium according to any one of the first to fifth aspects, a drive mechanism for supporting and rotating the perpendicular magnetic recording medium, and the perpendicular magnetic recording medium A magnetic head having an element for recording information, an element for reproducing recorded information, and a carriage assembly that movably supports the magnetic head with respect to a perpendicular magnetic recording medium. A magnetic recording / reproducing apparatus is provided.

  FIG. 2 is a partially exploded perspective view showing an example of the configuration of the magnetic recording / reproducing apparatus of the present invention.

  As shown in the figure, a rigid magnetic disk 121 for recording information according to the present invention is mounted on a spindle 122 and is driven to rotate at a constant rotational speed by a spindle motor (not shown). A slider 123 mounted with a single pole type recording head for recording information by accessing the magnetic disk 121 and an MR head for reproducing information is attached to the tip of a suspension 124 made of a thin plate spring. The suspension 124 is connected to one end side of an arm 125 having a bobbin portion for holding a drive coil (not shown).

  On the other end side of the arm 125, a voice coil motor 126, which is a kind of linear motor, is provided. The voice coil motor 126 is composed of a drive coil (not shown) wound around the bobbin portion of the arm 125, and a magnetic circuit composed of a permanent magnet and a counter yoke arranged so as to sandwich the coil.

  The arm 125 is held by ball bearings (not shown) provided at two locations above and below the fixed shaft 127, and is driven to rotate and swing by a voice coil motor 126. That is, the position of the slider 123 on the magnetic disk 121 is controlled by the voice coil motor 126. In FIG. 2, reference numeral 128 denotes a lid.

  Hereinafter, the present invention will be specifically described with reference to examples.

Example 1
As the nonmagnetic substrate 1, a glass substrate satisfying the standard specifications of a 2.5 inch magnetic disk was prepared.

  The nonmagnetic substrate was heated to 200 ° C., and the following layers were formed in this order by DC magnetron sputtering in an Ar atmosphere with a gas pressure of 0.6 Pa.

  First, a CrMo alloy having a thickness of 40 nm was formed as a nonmagnetic underlayer on the nonmagnetic substrate. On top of this, Co-22 at. % Cr-13 at. An in-plane hard magnetic layer was formed by sequentially laminating% Pt hard magnetic layers.

  Thereafter, a 0.7 nm thick Ru layer was formed as a nonmagnetic intermediate layer on the in-plane hard magnetic layer.

  Further, on the Ru layer, a Co-5 at. % Zr-10 at. A% Nb alloy was formed.

  On the in-plane soft magnetic layer, a Co-37 at. % Cr-8 at. % Pt alloy with a thickness of 20 nm and a perpendicular magnetic recording layer of Co-20 at. % Cr-10 at. % Pt-2at. % B alloy was successively formed with a thickness of 30 nm, and 7 nm of C was formed thereon as a protective layer to obtain a perpendicular magnetic recording medium.

  FIG. 3 is a cross-sectional view showing the configuration of the obtained perpendicular magnetic recording medium.

  As shown in the figure, this perpendicular magnetic recording medium has a nonmagnetic underlayer 6, an in-plane hard magnetic layer 7, a nonmagnetic intermediate layer 8, an in-plane soft magnetic layer 9, and a nonmagnetic underlayer 10 on a nonmagnetic substrate 1. The perpendicular magnetic recording layer 11 and the protective layer 12 are sequentially stacked.

  In this way, after the perpendicular magnetic recording medium continuously formed in the vacuum chamber is taken out into the atmosphere, the magnetized device using a specially produced electromagnet is used to outwardly protrude 15 kOe in the radial direction of the substrate on the disk. The in-plane hard magnetic layer was magnetized in the radial direction. The following perpendicular magnetic recording media are all magnetized unless otherwise specified.

  The recording / reproducing characteristics of the perpendicular magnetic recording medium thus manufactured were evaluated using a spin stand. As a recording / reproducing head, a single-pole head using a magnetoresistive effect is used as a reproducing element, a reproducing signal output S is a linear recording density of 50 kFCI, and a ratio of reproducing signal output to medium noise (S / Nm) is linear recording. Measurement was performed at a density of 400 kFCI.

  As a result, no spike noise was observed on the entire surface of the disk, and a good S / Nm value of 22 dB was obtained.

  When the recording / reproduction characteristics were similarly evaluated after the film formation and before the above-described magnetization, a plurality of spike noises having the same magnitude as the reproduction signal were observed. From this, it was found that by performing the magnetization operation, the in-plane hard magnetic layer was actually magnetized uniformly in the radial direction of the substrate, and the formation of the domain wall was suppressed.

  This perpendicular magnetic recording medium was incorporated in a magnetic recording / reproducing apparatus (HDD), and after performing a recording / reproducing operation, the medium was taken out from the HDD. Again, using a spin stand, the recording / reproducing characteristics after the recording / reproducing operation were evaluated.

  As a result, in the medium of Example 1, no spike noise was observed as in the case before the recording / reproducing operation, and no other deterioration of the recording / reproducing characteristics was particularly observed. From this, in Example 1, it is presumed that no demagnetization due to leakage magnetic flux from the VCM in the HDD occurred.

Comparative Example 1
A perpendicular magnetic recording medium was obtained in the same manner as in Example 1 except that the nonmagnetic intermediate layer was not formed between the in-plane hard magnetic layer and the in-plane soft magnetic layer. For the obtained perpendicular magnetic recording medium, the recording / reproducing characteristics before magnetization and before and after the recording / reproducing operation were evaluated in the same manner as in Example 1.

  As a result, no spike noise was observed on the entire disk surface before the recording / reproducing operation, and a good value of S / Nm of 22 dB was obtained.

  In the invention according to the fifth aspect, by providing the oxide layer, it is possible to moderately weaken the exchange coupling between the hard magnetic layer and the soft magnetic layer, and to suppress demagnetization due to an external magnetic field without increasing the medium noise. I can do it.

  In the magnetic recording medium after the recording / reproducing operation, a change was observed in which a plurality of spike noises having the same magnitude as the reproduced signal were observed at the outer peripheral portion of the disk. From this, it was presumed that in Comparative Example 1, the magnetization loss occurred at the outer peripheral portion of the disk due to the leakage magnetic flux from the VCM in the HDD.

  As described above, spike-like noise at the outer periphery of the disk was observed in Comparative Example 1, but not in Example 1. Therefore, a Ru nonmagnetic intermediate layer was placed between the in-plane hard magnetic layer and the in-plane soft magnetic layer. It has been found that the formation is effective for suppressing spike-like noise of the perpendicular magnetic recording medium, that is, preventing demagnetization.

Experimental example 1
Next, in order to investigate in detail the presence or absence of the occurrence of spike noise, the media of Experimental Example 1 and Comparative Experimental Example 1 were manufactured by paying attention to the magnetization state of the composite layer of the hard magnetic layer and the soft magnetic layer.

  As Experimental Example 1, a sample was prepared in the same manner as in Example 1, except that the CoCrPt nonmagnetic underlayer and the CoCrPtB perpendicular magnetic recording layer were not produced, but the C protective layer was formed directly on the CoZrNb in-plane soft magnetic layer. .

  Further, as Comparative Experimental Example 1, a sample similar to Comparative Example 1 was prepared, except that the CoCrPt nonmagnetic underlayer and the CoCrPtB perpendicular magnetic recording layer were not produced, and the C protective layer was formed directly on the CoZrNb in-plane soft magnetic layer. Produced.

  The samples of Comparative Experimental Example 1 and Experimental Example 1 were each incorporated in an HDD and continuously operated for 1 week while being kept at 75 ° C. in a thermostatic bath. Thereafter, each magnetic recording medium was taken out, and the magnetization direction on the surface of the soft magnetic layer was observed using an optical surface analyzer (OSA). The OSA observation results of Comparative Experimental Example 1 and Experimental Example 1 are shown in FIGS. 4 and 5, respectively.

  As shown in FIG. 4, the outer peripheral portion of the sample is white in FIG. 4, whereas FIG. 5 shows a uniform color on the entire surface of the sample. In the OSA evaluation results, it is difficult to specify the direction in which the magnetization is directed, but when the magnetic domains with different magnetization directions are in contact, the color appears different, so magnetization is performed in the radial direction. 5 and the presence or absence of spike noise, the magnetization of the portion reversed in white in FIG. 4 does not change from the initially magnetized state in FIG. We were able to estimate that it was off.

  Therefore, in the comparative experimental example 1 in which the in-plane soft magnetic layer was directly formed on the in-plane hard magnetic layer as a result of incorporating the samples of Experimental Example 1 and Comparative Experimental Example 1 into the HDD in the same manner as the magnetic recording medium. It was found that the out-of-magnetization (due to VCM) occurred in the outer peripheral portion, whereas the occurrence was suppressed in Experimental Example 1 in which the nonmagnetic intermediate layer was formed. Therefore, it has been found that the formation of the nonmagnetic intermediate layer between the in-plane hard magnetic layer and the in-plane soft magnetic layer is effective in preventing the perpendicular magnetic recording medium from being demagnetized.

In order to investigate in more detail the out-of-magnetization, the magnetic characteristics were evaluated using a vibrating sample magnetometer (VSM). For the perpendicular magnetic recording media of Experimental Example 1 and Comparative Experimental Example 1, the sample was cut into a 1 cm ² square around the middle periphery of the sample, and a magnetic field was applied in the in-film direction by VSM. The magnetization curves at this time are shown in FIG.

  In FIG. 6, although partially overlapping, the dotted line is a graph representing Comparative Experimental Example 1, and the solid line is a graph representing Experimental Example 1.

  As shown in FIG. 6, in Experimental Example 1, since the nonmagnetic intermediate layer is formed between the hard magnetic layer and the soft magnetic layer, the exchange interaction between these magnetic layers was weakened, so It was found that the hard magnetic layer was inverted after the majority of the magnetic layer was inverted. On the other hand, in Comparative Experimental Example 1, since the soft magnetic layer is directly formed on the hard magnetic layer, the exchange coupling interaction between these layers is strong, so that both layers are gradually reversed. I understood it.

  Model diagrams for explaining the magnetization state at this time are shown in FIGS. In both cases, the lower layer shows the hard magnetic layer 2 and the upper layer shows the soft magnetic layer 4, and the magnetization direction before applying the external magnetic field H as shown by the thick arrow is opposite to H as shown by the dotted arrow. Suppose that it was suitable. Arrow a represents the radial direction of the medium.

  7 and 8 show the magnetization states of the soft magnetic layer and the hard magnetic layer when an external magnetic field H opposite to the magnetization direction is applied to the magnetic recording media of Comparative Experimental Example 1 and Experimental Example 1, respectively. ing. 9 and 10 show the magnetization states of Comparative Experimental Example 1 and Experimental Example 1 after removing the external magnetic field (H = 0), respectively. Since the soft magnetic layer is easily affected by an external magnetic field, first, it is assumed that an external magnetic field is applied so that the magnetization of the soft magnetic layer is rotated by 90 °. Further, the double line between the arrows in FIG. 7 represents a case where the exchange coupling interaction is strong, and the dotted line between the arrows in FIG. 8 represents a case where the exchange coupling interaction is weak.

  At this time, in Comparative Experimental Example 1, since the exchange coupling interaction between both magnetic layers is strong, the hard magnetic layer is also dragged away from the original direction indicated by the dotted arrow as shown in FIG. After that, even if the external magnetic field is strengthened, the soft magnetic layer is basically reversed first, and then the hard magnetic layer is also reversed faster than the single case due to the strong exchange coupling interaction. . In such a magnetization reversal mechanism, when the magnetic field is removed from the state of FIG. 7, the state is as shown in FIG. 9, and the magnetization direction does not return to the original direction represented by the dotted arrow. From this, it can be seen that demagnetization occurs.

  In Experimental Example 1, as indicated by the dotted line between the arrows, the exchange coupling interaction between the two magnetic layers is weakened, so the hard magnetic layer is not dragged by the magnetization rotation of the soft magnetic layer and does not move from the original direction. . However, when the external magnetic field is further strengthened after that, since the magnetic coupling is performed to some extent, the hard magnetic layer is dragged by the soft magnetic layer and the magnetic field is weaker than that of the single case. It will be reversed. Further, in the case of such a magnetization reversal mechanism, when the magnetic field is removed from the state of FIG. 8, it returns to the original magnetization direction as shown in FIG.

  The difference between the magnetization curves of Comparative Experimental Example 1 and Experimental Example 1 shown in FIG. 6 is considered to arise from the above-described magnetization reversal mechanism. That is, in general, it can be said that when the exchange coupling between the hard magnetic layer and the soft magnetic layer is strong, it becomes a magnetization curve as in Comparative Experiment Example 1, and when it is weak, it becomes a magnetization curve as in Experiment Example 1. Further, from the same concept as described in FIGS. 7 to 10, when the exchange coupling between the hard magnetic layer and the soft magnetic layer is strong, demagnetization tends to occur, and when it is weak, demagnetization occurs. It can be estimated that it becomes difficult.

  Accordingly, in Example 1 and Experimental Example 1, the non-magnetic layer was prevented by forming a nonmagnetic layer between the hard magnetic layer and the soft magnetic layer. This is likely to occur when the exchange coupling between the two magnetic layers is strong as in FIG. 2, and it can be said that prevention of demagnetization is achieved by weakening the exchange coupling. Therefore, it can be seen that weakening the exchange coupling between the hard magnetic layer and the soft magnetic layer has an effect on prevention of demagnetization of the perpendicular magnetic recording medium.

On the other hand, in FIG. 6, the most different point between the magnetization curves of Comparative Experimental Example 1 and Experimental Example 1 is the vicinity indicated by Hc ^Hard at the top of the figure. The dotted line shows the position where the saturation magnetization of only the hard magnetic layer is subtracted from the saturation magnetization of the entire composite layer of the hard magnetic layer and the soft magnetic layer, and the intersection of this dotted line and each magnetization curve is substantially It is considered that it corresponds to the coercive force Hc of only a hard magnetic layer. Therefore, hereinafter, for convenience, this value will be referred to as Hc ^Hard and used as a measure of the exchange coupling strength between the hard magnetic layer and the soft magnetic layer.

When a nonmagnetic layer is formed between two ferromagnetic layers as in Experimental Example 1, the strength (absolute value) of the exchange interaction decreases with an increase in the thickness of the nonmagnetic layer. When the nonmagnetic layer thickness is 0 and the interaction is maximum as in Comparative Experimental Example 1, Hc ^Hard is minimized, and when the nonmagnetic layer thickness is sufficiently thick and there is no interaction, Hc ^Hard is only the hard magnetic layer. Is equal to the value of Hc. Therefore, in order to obtain exchange coupling with a desired strength, it is important to examine the change in Hc ^Hard with respect to the nonmagnetic layer thickness.

Experimental example 2
As Experimental Example 2, several samples were produced in the same manner as in Experimental Example 1 except that the Ru layer was formed as a nonmagnetic intermediate layer by changing the thickness in the range of 0 to 2 nm.

FIG. 12 shows the result of evaluating the Hc ^Hard of the obtained sample by VSM and examining its nonmagnetic layer thickness dependency.

From FIG. 12, it can be seen that the value of Hc ^Hard increases monotonously from the Ru layer thickness of 0 nm and saturates when it exceeds 1 nm. Usually, in a thin film in which a ferromagnetic transition metal and a nonmagnetic metal are multilayered, ferromagnetic and antiferromagnetic coupling appear periodically with respect to the thickness of the nonmagnetic layer. Therefore, this Hc ^Hard value is also periodic. Although no antiferromagnetically coupled state was observed from the shape of the magnetization curve, all the media produced in Experimental Example 2 were ferromagnetically coupled. It is thought that there is. For example, when Ru is used as a nonmagnetic intermediate layer between ferromagnetic layers, it is generally known that antiferromagnetic coupling can be obtained with a layer thickness of about 0.8 nm. However, the sample having a layer thickness of about 0.8 nm according to this experimental example was not particularly different from a sample having another layer thickness that is considered to be ferromagnetically coupled.

In FIG. 12, the saturation value of Hc ^Hard was about 2.8 kOe which is almost equal to Hc of only the hard magnetic layer. For this reason, it is considered that there is almost no influence on the hard magnetic layer from the soft magnetic layer in this region. When the Ru layer thickness is 1 nm or more, the hard magnetic layer and the soft magnetic layer are hardly exchange-coupled. In this sample, the magnetization of the soft magnetic layer is uniformly fixed in the radial direction by magnetization. Therefore, it can be determined that the Ru layer thickness is preferably 1 nm or less.

On the other hand, since the effect of suppressing the demagnetization can be obtained regardless of the thickness of the nonmagnetic layer, the minimum value of the nonmagnetic layer thickness is about 0.2 nm, which is about 1 atomic layer. It is considered preferable. However, since the effect of suppressing demagnetization is greater when the strength of exchange coupling is smaller, the Ru layer thickness is more preferably 0.5 as judged from the magnitude of Hc ^Hard in the graph of FIG. Or about 0.9 nm.

  Here, considering the magnetization curve of FIG. 6 and the magnetization reversal mechanism as shown in FIGS. 7 to 10, the VCM in the HDD is demagnetized by the leakage magnetic field of the VCM in the magnetization direction of the medium, for example, radially outward. It can be seen that it does not occur when the direction is the same as, and is likely to occur when the direction is reverse, for example, inward in the radial direction.

0.5nm thickness of the Ru layer of the in Experimental Example 2, the samples that do not form a sample and Ru layer of 0.8 nm, was examined with magnetic field ^{H R} magnetization recovery rate.

Figure 11 shows a diagram illustrating an example of a magnetization curve for explaining the definition of the magnetic field H ^R magnetization recovery rate.

  As shown at point A in the figure, the magnet was once magnetized to saturation using VSM. Thereafter, similarly to the leakage magnetic field in the reverse direction by the VCM, a magnetic field in the reverse direction to the remanent magnetization direction was applied, and the ease of occurrence of demagnetization was examined.

First, in the magnetization curves relating to these samples, as shown by the point B, the state of the residual magnetization Mr on the major loop was set. Thereafter, the residual magnetization as shown in point C from the application of the reverse of the (negative) field H ^R, was calculated residual magnetization value Mr ^R when returning to 0 as shown at point D.

Here, a value obtained by dividing the residual magnetization value Mr ^R by Mr, that is, Mr ^R / Mr is defined as a magnetization recovery rate. We examined the change in the magnetization recovery rate for H ^R. In this magnetization recovery rate, for example, a magnetic field is applied until saturation in the negative direction, and the magnetization recovery rate in a state where the magnetization is not recovered at all, that is, in a completely reversed state is -1.

The residual magnetization a graph showing the relationship between the reverse (negative) field H ^R and the magnetization recovery ratio in FIG. In the figure, the curve 103 indicates the case without the Ru layer, and the curves 102 and 101 indicate the cases when the Ru layer is 0.5 nm and 0.8 nm, respectively.

From the graph of FIG. 13, it can be considered that no demagnetization has occurred in any sample because the residual magnetic field returns almost to the original value even when a reverse magnetic field is applied up to −0.2 kOe. , and the magnetic field H ^R of more reverse direction is increased, the thinner the medium of the Ru layer thickness, fast magnetization recovery rate is lowered, pinning failure was found to be likely to occur.

  As shown in FIG. 12, when the Ru layer thickness exceeds 1 nm, exchange coupling between the hard magnetic layer and the soft magnetic layer hardly works as can be seen from FIG. It is difficult to carry out, and it is difficult to stably direct the magnetization of the soft magnetic layer in one direction.

  As described above, from Experimental Example 2, the formation of a thicker nonmagnetic intermediate layer within a range in which sufficient magnetization can be performed between the hard magnetic layer and the soft magnetic layer is an effect of demagnetization of the perpendicular magnetic recording medium. It turned out to be effective in terms of suppression.

  Further, regarding Ru, the layer thickness capable of sufficient magnetization is preferably estimated to be about 0 to about 0.9 nm, and the more preferable Ru layer thickness is about 0.5 nm to about 0 from the viewpoint of both magnetization strength and magnetization recovery rate. .9 nm.

From the above results, it is clear that as the strength of the exchange interaction is reduced, the demagnetization can be suppressed and the magnetization recovery rate can be increased. Since the Hc ^Hard increases as the magnitude of the exchange coupling interaction decreases, there is a correlation between the magnetization recovery rate and Hc ^Hard, and in order to increase the magnetization recovery rate and make it difficult to cause demagnetization. , Hc ^Hard was found to be larger.

For example, if one of the means for reducing the exchange coupling between the hard magnetic layer and the soft magnetic layer is to form a nonmagnetic intermediate layer between the two magnetic layers, it is determined by examining the dependence of Hc ^{Hard on} the thickness of the nonmagnetic layer. A preferable nonmagnetic layer thickness that achieves both a magnetic effect and resistance to demagnetization can be roughly determined.

Experimental Example 3 and Comparative Experimental Example 2
As Experimental Example 3, several samples were produced in the same manner as in Experimental Example 1 except that the CoCrPt hard magnetic layer thickness was changed to 50, 35, 20, and 15 nm.

  In Comparative Experiment Example 2, several samples were produced in the same manner as Comparative Experiment Example 1 except that the CoCrPt hard magnetic layer thickness was changed to 50, 35, and 20 nm.

The samples of Example 3 and Comparative Example 2, the results of examining the change in the magnetization recovery rate for H ^R by VSM, respectively shown in FIGS. 14 and 15. In FIG. 15, curves 104, 105, and 106 indicate cases where the CoCrPt hard magnetic layer thicknesses are 20 nm, 35 nm, and 50 nm, respectively. In FIG. 14, curves 107, 108, and 109 indicate cases where the CoCrPt hard magnetic layer thicknesses are 15 nm, 20 nm, 35 nm, and 50 nm, respectively.

From FIG. 15, in Comparative Experimental Example 2, as the thickness of the hard magnetic layer is decreased, the magnetization recovery rate is decreased, the resistance to demagnetization is decreased, and even the magnetization effect cannot be sufficiently obtained at 20 nm. I understood that. On the other hand, as shown in FIG. 14, in Experimental Example 3, the magnetization recovery rate is greatly reduced when the thickness of the hard magnetic layer is reduced to 15 nm. than 50nm of the medium in example 3 were found to be maintained high magnetization recovery rate to large H ^R.

  It has been found that the CoCrPt hard magnetic layer used has magnetic properties such as in-plane coercivity and in-plane squareness ratio that are clearly reduced when the layer thickness is 20 nm or less. The decrease in the magnetization recovery rate at 15 nm of the hard magnetic layer thickness in Experimental Example 3 is attributed to this, and if a hard magnetic layer having good magnetic properties even when the layer thickness is 10 nm or less is used, the magnetization recovery as shown in FIG. It is estimated that the rate deterioration can be prevented. For this reason, in Experiment 3, the minimum value of the hard magnetic layer thickness that can maintain a high recovery rate is 20 nm. However, considering the characteristics of the hard magnetic layer, the thickness can be reduced to 10 nm or less. Is fully possible.

  Therefore, reducing the exchange coupling between the hard magnetic layer and the soft magnetic layer by providing a nonmagnetic intermediate layer such as a Ru layer can prevent demagnetization by reducing the thickness of the hard magnetic layer and improving the magnetization recovery rate. It can be seen that there is an effect of achieving both.

Comparative Example 2
As Comparative Example 2, a perpendicular magnetic recording medium was manufactured in the same manner as Comparative Example 1 except that the CoCrPt hard magnetic layer thickness was changed to 50, 35, and 20 nm.

  When the recording / reproduction characteristics of the obtained magnetic recording medium were evaluated using a spin stand, spike-like noise was not observed in the media having CoCrPt hard magnetic layer thicknesses of 50 and 35 nm. However, a plurality of spike noises were observed in the 20 nm medium with the thin hard magnetic layer. This is considered to be because a sufficient magnetization effect was not obtained, and therefore the recording / reproducing characteristics could not be sufficiently evaluated. On the other hand, the S / Nm of the medium having a hard magnetic layer thickness of 50 and 35 nm was 22 and 24 dB, respectively, which was equal to or better than that of Comparative Example 1. Therefore, it has been found that reducing the hard magnetic layer thickness to some extent is effective in improving the medium noise of the perpendicular magnetic recording medium.

  The perpendicular magnetic recording medium of Comparative Example 2 was incorporated in the HDD, and after performing the recording / reproducing operation, the medium was taken out from the HDD, and the recording / reproducing characteristics were evaluated again using a spin stand. As a result, a change was observed in which a plurality of spike-like noises having the same magnitude as the reproduced signal were observed on the outer periphery of every disk. From this, it was presumed that in Comparative Example 2, the magnetization was lost at the outer peripheral portion of the disk due to the leakage magnetic flux from the VCM in the HDD regardless of the thickness of the hard magnetic layer.

Example 2
As Example 2, a perpendicular magnetic recording medium was manufactured in the same manner as in Example 1 except that the thickness of the CoCrPt hard magnetic layer was changed to 50, 35, 20 and 15 nm. When the recording / reproduction characteristics of the obtained magnetic recording medium were evaluated using a spin stand, spike-like noise was not observed in the media with CoCrPt hard magnetic layer thicknesses of 50, 35, and 20 nm. Some spike-like noise was observed in the medium with the thinnest hard magnetic layer having a thickness of 15 nm. This is due to the magnetic characteristics of the hard magnetic film used, as shown in Experimental Example 3, and is thought to be due to the occurrence of demagnetization. Therefore, the recording / reproducing characteristics cannot be fully evaluated. It was. On the other hand, the S / Nm of the medium having a hard magnetic layer thickness of 50, 35, and 20 nm was 22, 24, and 26 dB, respectively, which were as good as or better than Example 1. Therefore, it has been found that reducing the hard magnetic layer thickness to some extent is effective in improving the medium noise of the perpendicular magnetic recording medium.

  Each of the perpendicular magnetic recording media was incorporated in the HDD, and after performing the recording / reproducing operation, the medium was taken out from the HDD, and the recording / reproducing characteristics were evaluated again using a spin stand. As a result, in the medium of Example 5, except for the medium having a hard magnetic layer thickness of 15 nm, no spike noise was observed as in the case before the recording / reproducing operation, and no other deterioration of the recording / reproducing characteristics was observed. From this, it is presumed that the medium other than the hard magnetic layer thickness of 15 nm in Example 5 did not cause demagnetization due to the leakage magnetic flux from the VCM in the HDD.

  Therefore, for the medium having a hard magnetic layer thickness of 50 to 20 nm, spike-like noise was observed in Comparative Example 2 and demagnetization occurred, but this was not observed in Example 2. In addition, reducing the exchange coupling between the soft magnetic layers and improving the resistance to demagnetization, while reducing the thickness of the hard magnetic layer suppresses spike noise in the perpendicular magnetic recording medium and prevents the demagnetization. It turned out to be effective.

Experimental Example 4
A sample was prepared in the same manner as in Experimental Example 1 except that the thickness of the CoZrNb soft magnetic layer was 20 nm. FIG. 16 shows the result of measuring the magnetization curve in the in-plane direction of the obtained sample using VSM. Compared with the magnetization curve of FIG. 6, it is basically the same in that the hard magnetic layer is reversed after the majority of the soft magnetic layer is reversed first, but the coercive force of the portion corresponding to the soft magnetic layer is increased. As a result, it was found that sufficient soft magnetic properties were not exhibited.

Example 3 and Experimental Example 5
A perpendicular magnetic recording medium similar to Examples 1 and 2 and samples similar to Experimental Examples 1 to 4 were prepared except that V, Cr, Cu, Mo and Rh were used instead of the Ru nonmagnetic intermediate layer, respectively. When the same experiment was conducted, almost the same result was obtained. ^However, the non-magnetic layer thickness dependency of ^{Hc Hard,} and near 0.6~0.7nm nonmagnetic layer thickness also is for any medium, the result that ^{Hc Hard} is saturated with a thin layer thickness than in the case of Ru Obtained.

  For this reason, it is generally considered that the range of the thickness of the nonmagnetic intermediate layer in which the magnetization effect and the resistance to demagnetization are compatible is preferably 0.3 to 0.5 nm.

Example 4 and Experimental Example 6
Except that Co was added to the Ru nonmagnetic intermediate layer to obtain a CoRu alloy intermediate layer, perpendicular magnetic recording media similar to those in Examples 1 and 2 and Experimental Examples 1 to 4 were manufactured and the same experiment was performed. Almost similar results were obtained.

However, Co-40 at. As a result of investigating the dependence of Hc ^{Hard on} the CoCr alloy layer thickness for% Ru, it was found that Hc ^Hard saturates in the vicinity of 5 nm where the CoCr alloy layer thickness is thicker than in the case of Ru. In view of both the magnetization strength and the magnetization recovery rate, the preferable thickness of the Co-containing alloy nonmagnetic intermediate layer is considered to be 1 to 5 nm.

Furthermore, when the composition of Co was increased to give a weak magnetism of saturation magnetization of 10 to 60 emu / cm ³ , the saturation layer thickness tended to increase further as Co increased, that is, the saturation magnetization increased. However, the basic tendency has not changed, and it has been possible to achieve both the magnetization effect and the resistance to demagnetization.

Example 5 and Experimental Example 7
A perpendicular magnetic recording medium similar to that in Examples 1 and 2 and Experimental Examples 1 to 4 was produced and the same experiment was performed except that a CoCr alloy intermediate layer was used instead of the Ru nonmagnetic intermediate layer. Similar results were obtained.

However, Co-40 at. As a result of investigating the dependence of Hc ^{Hard on} the CoCr alloy layer thickness for% Cr, it was found that Hc ^Hard saturates in the vicinity of 5 nm, where the CoCr alloy layer thickness is thicker than in the case of Ru. In view of both the magnetization strength and the magnetization recovery rate, the preferable thickness of the Co-containing alloy nonmagnetic intermediate layer is considered to be 1 to 5 nm.

Furthermore, when the composition of Co was increased to give a weak magnetism of saturation magnetization of 10 to 60 emu / cm ³ , the saturation layer thickness tended to increase further as Co increased, that is, the saturation magnetization increased. However, the basic tendency has not changed, and it has been possible to achieve both the magnetization effect and the resistance to demagnetization.

  Further, similar results were obtained even when Pt, B, and Ta were added to the CoCr alloy intermediate layer.

In addition, since the saturation magnetization of the CoCrPt hard magnetic layer used in the examples was about 240 emu / cc, good characteristics can be obtained if the saturation magnetization of the weak magnetic intermediate layer is less than a quarter of that of the hard magnetic layer. It is considered to be obtained. This time, no experiment was performed on an intermediate layer having a saturation magnetization of 60 emu / cm ³ or more. However, if the saturation magnetization is smaller than that of the hard magnetic layer, the same effect can be obtained in principle.

  From the above results, it was found that the optimum film thickness was increased by using a weak magnetic material with some magnetism rather than using a nonmagnetic material for the intermediate layer.

Example 6
Instead of forming a Ru non-magnetic intermediate layer, after laminating an in-plane hard magnetic layer, oxygen is introduced into the chamber to oxidize the surface, and an oxide layer is formed between the in-plane hard magnetic layer and the in-plane soft magnetic layer. A perpendicular magnetic recording medium was manufactured in the same manner as in Example 1 except that.

  When the recording / reproduction characteristics of the obtained magnetic recording medium were evaluated using a spin stand, no spike noise was observed on the entire disk surface, and the S / Nm was 22 dB, which was a good value equivalent to that in Example 1. Indicated.

  This perpendicular magnetic recording medium was incorporated in the HDD, and after recording / reproducing operation, the medium was taken out from the HDD, and recording / reproducing characteristics were evaluated again using a spin stand. As a result, no spike-like noise was observed as before the recording / reproducing operation, and no other deterioration of the recording / reproducing characteristics was observed. From this, it is presumed that in this magnetic recording medium, no demagnetization due to leakage magnetic flux from the VCM in the HDD occurred.

  Therefore, spike-like noise due to demagnetization was observed in the outer peripheral portion of the disk in Comparative Example 1 and not in Example 6. Therefore, an oxide layer was formed between the in-plane hard magnetic layer and the in-plane soft magnetic layer. This has been found to be effective in preventing the magnetization of the perpendicular magnetic recording medium from coming off.

The figure showing an example of a structure of the magnetic recording medium of this invention 1 is a partially exploded perspective view of an example of the configuration of a magnetic recording / reproducing apparatus of the present invention. The figure showing another example of a structure of the magnetic recording medium of this invention A photograph showing an OSA observation result of an example of a sample according to a conventional example A photograph showing an OSA observation result of an example of a sample according to the present invention Magnetization curves of the samples shown in FIGS. Model diagram for explaining the magnetization state of the conventional example Model diagram for explaining the magnetization state of the magnetic recording medium of the present invention Model diagram for explaining the magnetization state of the conventional example Model diagram for explaining the magnetization state of the magnetic recording medium of the present invention Diagram illustrating the definition of the magnetic field H ^R magnetization recovery rate Graph showing the relationship between non-magnetic layer thickness and Hc ^Hard Graph showing the relationship between the magnetic field H ^R and the magnetization recovery ratio Change in the magnetization recovery rate for H ^R of the magnetic recording medium of the present invention Change in the magnetization recovery rate for H ^R of a conventional magnetic recording medium Magnetization curves of other samples according to the invention

Explanation of symbols

        DESCRIPTION OF SYMBOLS 1 ... Substrate, 2, 7 ... In-plane hard magnetic layer, 3, 8 ... Intermediate layer, 4, 9 ... In-plane soft magnetic layer, 5, 11 ... Magnetic recording layer, 10 ... Nonmagnetic underlayer, 12 ... Protective layer , 121 ... Magnetic disk, 122 ... Spindle, 123 ... Slider, 124 ... Suspension, 125 ... Arm, 126 ... Voice coil motor, 127 ... Fixed shaft

Claims (26)

In a perpendicular magnetic recording medium in which an in-plane hard magnetic layer, an in-plane soft magnetic layer, and a perpendicular magnetic recording layer are sequentially laminated on a substrate, the in- plane hard magnetic layer has a thickness of 50 nm or less, The in-plane hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled to each other as compared with the case where the in-plane soft magnetic layer is directly formed on the uniform in-plane hard magnetic layer. Perpendicular magnetic recording medium. In the magnetic characteristics of the composite layer portion of the in- plane hard magnetic layer and the in-plane soft magnetic layer, the substantial coercive force of the in-plane hard magnetic layer is directly on the uniform in-plane hard magnetic layer. 2. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is larger than the case where the in-plane soft magnetic layer is formed . The perpendicular magnetic recording medium according to claim 2, substantial coercivity of the in-plane hard magnetic layer may be smaller than the uniform the in-plane hard magnetic layer alone coercivity. Substrate, is formed on the substrate in-plane hard magnetic layer having a thickness of less than 50 nm, is provided on the said surface hard magnetic layer, a magnetic layer having a saturation magnetization smaller than said surface hard magnetic layer, the The in-plane soft magnetic layer provided on the magnetic layer and the perpendicular magnetic recording layer are provided, and the in-plane soft magnetic layer is formed directly on the uniform in-plane hard magnetic layer. A perpendicular magnetic recording medium characterized in that a hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled . 5. The perpendicular magnetic recording medium according to claim 4, wherein the magnetic layer has a saturation magnetization of ¼ or less of the saturation magnetization of the in-plane hard magnetism . The perpendicular magnetic recording medium according to claim 4, wherein the magnetic layer has a saturation magnetization of 60 emu / cc . The perpendicular magnetic recording medium according to claim 4, wherein the magnetic layer includes at least one selected from the group consisting of iron, cobalt, and nickel . The perpendicular magnetic recording medium according to claim 7, wherein the magnetic layer is an alloy mainly containing cobalt and ruthenium . The perpendicular magnetic recording medium according to claim 7 , wherein the magnetic layer is an alloy mainly containing cobalt and chromium . The perpendicular magnetic recording medium according to claim 7 , wherein the magnetic layer further includes at least one selected from the group consisting of platinum, boron, and tantalum . Substrate, is formed on the substrate in-plane hard magnetic layer having a thickness of less than 50 nm, is provided on the said surface hard magnetic layer, a nonmagnetic layer mainly containing cobalt, provided on the nonmagnetic layer And a perpendicular magnetic recording layer provided on the in-plane soft magnetic layer, and the in-plane soft magnetic layer is directly formed on the uniform in-plane hard magnetic layer. In the perpendicular magnetic recording medium , the in-plane hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled . The perpendicular magnetic recording medium according to claim 11, wherein the nonmagnetic layer further includes ruthenium . The perpendicular magnetic recording medium according to claim 11, wherein the nonmagnetic layer further contains chromium . The non-magnetic layer, a perpendicular magnetic recording medium according to any one of claims 11 to 13, characterized in that it has a thickness of 1 to 5 nm. A substrate, an in-plane hard magnetic layer formed on the substrate and having a thickness of 50 nm or less, provided on the in-plane hard magnetic layer, mainly containing ruthenium and having a thickness of 0.5 nm to 0.9 nm On the uniform in- plane hard magnetic layer , comprising: a non-magnetic layer comprising: an in - plane soft magnetic layer provided on the non-magnetic layer; and a perpendicular magnetic recording layer provided on the in- plane soft magnetic layer. direct the plane than the case of forming a soft magnetic layer, a perpendicular magnetic recording medium characterized Rukoto said plane hard magnetic layer and the in-plane soft magnetic layer has been weakly exchange coupling. A substrate, an in-plane hard magnetic layer formed on the substrate and having a thickness of 50 nm or less, a nonmagnetic layer having a thickness of less than 0.5 nm provided on the in-plane hard magnetic layer, on the nonmagnetic layer An in-plane soft magnetic layer and a perpendicular magnetic recording layer provided on the in-plane soft magnetic layer, and the in-plane soft magnetic layer is formed directly on the uniform in-plane hard magnetic layer. The perpendicular magnetic recording medium is characterized in that the in-plane hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled to each other . The perpendicular magnetic recording medium according to claim 16, wherein the nonmagnetic layer includes at least one selected from the group consisting of vanadium, chromium, copper, molybdenum, and rhodium . The non-magnetic layer, a perpendicular magnetic recording medium according to claim 1 6 or 17, characterized in that it has a thickness of less than or 0.3 nm 0.5 nm. A substrate, an in-plane hard magnetic layer formed on the substrate and having a thickness of 50 nm or less, an oxide layer of the in-plane hard magnetic layer provided on the in-plane hard magnetic layer, and provided on the oxide layer And a perpendicular magnetic recording layer provided on the in-plane soft magnetic layer, and the in- plane soft magnetic layer is directly formed on the uniform in-plane hard magnetic layer. In the perpendicular magnetic recording medium , the in-plane hard magnetic layer and the in-plane soft magnetic layer are weakly exchange-coupled . The perpendicular magnetic recording medium according to claim 1, wherein the in-plane hard magnetic layer has a thickness of 5 to 50 nm . The plane soft magnetic layer, a perpendicular magnetic recording medium according to any one of claims 1 to 20, characterized in that it has a more 20nm thickness. The perpendicular magnetic recording medium according to claim 21 wherein the plane soft magnetic layer, to not 20nm characterized by having a thickness of 500 nm. The perpendicular magnetic recording medium according to any one of claims 1 to 22, wherein the in-plane hard magnetic layer is an alloy mainly composed of cobalt, chromium, and platinum . 24. The perpendicular magnetic recording medium according to claim 23, wherein the in-plane hard magnetic layer further includes at least one selected from the group consisting of palladium, ruthenium, and rhodium. The perpendicular magnetic recording medium according to claim 1, wherein the in-plane hard magnetic layer is magnetized in the same direction as the in-plane soft magnetic layer. 26. The perpendicular magnetic recording medium according to claim 1, a drive mechanism for supporting and rotating the perpendicular magnetic recording medium, and an element for recording information on the perpendicular magnetic recording medium And a magnetic head having an element for reproducing recorded information, and a carriage assembly that movably supports the magnetic head with respect to the perpendicular magnetic recording medium. apparatus.

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