JP2007134004A - Heat assisted magnetic recording medium and heat assisted magnetic recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat assisted magnetic recording medium suitable for suppressing heat expansion in a track crossing direction in a recording layer during information recording, and to provide a heat assisted magnetic recording device provided with the heat assisted magnetic recording medium. <P>SOLUTION: The heat assisted magnetic recording medium 10 has the recording layer 12 and is rotated during information recording. The recording layer 12 includes a plurality of streaks of recording magnetic part 12a extending in parallel around a rotational center of rotational operation and a non-magnetic part 12b interposed between the streaks of the recording magnetic part 12a adjacent to each other. The thermal conductivity of the non-magnetic part 12b is 1/100 times as high as the thermal conductivity of the recording magnetic part 12a or lower. The heat assisted magnetic recording device X is provided with the heat assisted magnetic recording medium 10, a magnetic field applying means for applying a magnetic field to the heat assisted magnetic recording medium and a heating means for locally heating the heat assisted magnetic recording medium 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium and a magnetic recording apparatus that are accompanied by thermal assistance during information recording.

  A magnetic disk (magnetic recording medium) is known as a recording medium for configuring a storage device such as a hard disk. The magnetic disk has a laminated structure including a disk substrate and a recording layer having a predetermined magnetic structure. With the increase in the amount of information processing in computer systems, there is a growing demand for higher recording density for magnetic disks.

  When recording information on the magnetic disk, a recording magnetic head is disposed close to the recording surface of the magnetic disk (substantially composed of a recording layer), and the magnetic head maintains the recording layer on the recording layer. A recording magnetic field stronger than the magnetic force is applied. By reversing the direction of the recording magnetic field from the magnetic head sequentially while moving the magnetic head relative to the magnetic disk, a plurality of recording marks (magnetic domains) whose magnetization directions are sequentially reversed are recorded in the circumferential direction of the magnetic disk. Or it is formed continuously in the track extending direction. At this time, by controlling the timing of reversing the recording magnetic field direction, a recording mark is formed with a predetermined length in each. In this way, a predetermined signal or information is recorded as a change in the magnetization direction in the recording layer.

  In the technical field of magnetic disks, it is known that the higher the coercivity of the recording layer, the higher the thermal stability of the magnetic domain formed in the recording layer, and the easier it is to form a stable magnetic domain that is minute or narrow. . The smaller the minimum magnetic domain (minimum recording mark) that can be stably formed in the recording layer, the higher the recording density can be obtained on the magnetic disk.

  In recording information on a magnetic disk, as described above, a recording mark cannot be properly formed unless a recording magnetic field stronger than the coercive force of the recording layer is applied. For this reason, it is conceivable to increase the strength of the recording magnetic field to be applied by the magnetic head as the coercive force set for the recording layer increases. However, the strength of the recording magnetic field that can be applied by the magnetic head is restricted, for example, from the viewpoint of the structure of the magnetic head and power consumption.

  Thus, in recording information on the magnetic disk, a so-called heat-assisted magnetic recording method may be employed. When information recording is performed on a magnetic disk by the heat-assisted magnetic recording method, for example, the recording layer of the magnetic disk is locally irradiated by laser irradiation from a predetermined optical head arranged close to the recording surface of the rotating magnetic disk. Heated sequentially. In the recording layer, the coercive force is lower in the region heated by heating than in the surrounding non-heated region. Then, a magnetic field that is stronger than the coercive force of the temperature rising area of the recording layer is applied to the temperature rising area by the magnetic head disposed close to the recording surface of the magnetic disk, and a part of the temperature rising area is magnetized in a predetermined direction. Is done. This magnetization is fixed in the course of cooling the magnetized portion. In the heat-assisted magnetic recording system, in this way, a plurality of recording marks (magnetic domains) each having a predetermined length corresponding to a recording signal are reversed along a track extending in the circumferential direction of the disk. It is formed. In a heat-assisted magnetic recording type magnetic disk, information recording is performed by applying a recording magnetic field to a portion where the coercive force has been reduced by heating in the recording layer, so that the recording layer at room temperature during information retention or information reproduction Even when the coercive force is set high, it is not necessary to excessively increase the intensity of the recording magnetic field to be applied by the magnetic head. Such a heat-assisted magnetic disk is described in, for example, Patent Document 1 and Patent Document 2 below.

JP-A-6-243527 JP 2003-157502 A

  When a recording-scheduled part in the recording layer is heated at the time of information recording on the heat-assisted magnetic disk, the temperature around the recording-scheduled part is also significantly increased. On the other hand, in the heat-assisted magnetic disk, from the viewpoint of increasing the recording density, it is preferable that the recording layer has a high coercive force. There is a need to. However, in the conventional heat-assisted magnetic disk, when information is recorded, if the degree of heating is too strong and the temperature rise range above the predetermined temperature in the recording layer is too wide, the track next to the track on which the recording marks are sequentially formed is reached. There may be a cross-write phenomenon in which the recording mark of the adjacent track is at least partially overwritten due to the unduly widening of the recording mark width and the recording mark of the adjacent track disappears or deteriorates. The cross write phenomenon is not preferable from the viewpoint of increasing the recording density of the magnetic disk because it hinders the narrowing of the track pitch. Thus, the conventional heat-assisted magnetic disk (heat-assisted magnetic recording medium) has difficulty in increasing the recording density.

  The present invention has been conceived under the circumstances as described above, and a heat-assisted magnetic recording medium suitable for suppressing the spread of heat in the track crossing direction in the recording layer during information recording, It is another object of the present invention to provide a heat-assisted magnetic recording apparatus including such a medium.

  According to the first aspect of the present invention, there is provided a heat-assisted magnetic recording medium having a recording layer and rotating during information recording. In this thermally-assisted magnetic recording medium, the recording layer includes a plurality of recording magnetic portions extending in parallel around the rotation center of the rotational operation and a nonmagnetic portion interposed between adjacent recording magnetic portions, and is nonmagnetic. The thermal conductivity of the part is 1/100 or less of the thermal conductivity of the recording magnetic part.

  In the present heat-assisted magnetic recording medium, an information track is set in the recording magnetic portion, and at the time of information recording, recording marks are sequentially formed on a predetermined information track (recording magnetic portion) by the heat-assisted magnetic recording method. In the recording layer, there is information between an information track (first information track) in which information recording is in progress and locally heated sequentially and another information track (second information track) adjacent thereto. A non-magnetic part having a thermal conductivity of 1/100 or less of the thermal conductivity of the track (recording magnetic part) is interposed. Therefore, propagation of heat supplied from the first information track to the second information track by the heating means for the purpose of raising the temperature of the first information track is suppressed to a considerable extent. Therefore, according to this magnetic recording medium, the spread of heat in the track crossing direction in the recording layer can be appropriately suppressed during information recording.

  Further, in this magnetic recording medium, the first information track to which the magnetic field is sequentially applied and the adjacent second information track in the recording layer at the time of information recording are applied by the nonmagnetic portion. It is divided. Therefore, the influence of the recording magnetic field applied by the recording element (magnetic field applying means) on the first information track is considerably attenuated. The magnetic influence of signal leakage from the recording marks recorded on the second information track when the signal of the first information track is reproduced is considerably attenuated.

  The magnetic recording medium as described above is suitable for preventing or suppressing the occurrence of the cross-write phenomenon to reduce the track pitch or increase the recording density.

  In addition, in this magnetic recording medium, the recording layer is utilized by utilizing the fact that the heat propagation from the first information track to the second information track, in which information recording is in progress and locally heated sequentially, is suppressed. It is possible to generate a temperature distribution represented by a plurality of isotherms that are non-circular and approximate to a rectangle. Specifically, in this magnetic recording medium, the temperature distribution in which the shape in each isotherm is expressed by a plurality of isotherms linear in both the track width direction and the track extension direction, and the temperature change is small over the entire track width. Can be generated in the recording layer. In the conventional heat-assisted magnetic recording medium, in the recording layer at the time of information recording, a temperature distribution represented by a plurality of circular isotherms is generated in the recording layer. It is known that when a recording magnetic field is sequentially applied to information tracks under such temperature distribution conditions, so-called arrow-shaped recording marks are sequentially formed along the information track. On the other hand, in the heat-assisted magnetic recording medium of the present invention, a temperature distribution represented by a plurality of isotherms approximating the rectangle as described above can be generated in the recording layer during information recording. The recording marks can be sequentially formed along the information track. The rectangular recording mark is more suitable for miniaturizing the mark transition width (the actual recording mark length in the track extending direction) than the conventional arrow feather-shaped recording mark, and therefore the linear recording density (track) of the medium. This is suitable for improving the recording density in the extending direction. Therefore, this magnetic recording medium is suitable for increasing the recording density by miniaturizing the recording marks.

  According to a second aspect of the present invention, a thermally assisted magnetic recording apparatus is provided. The heat-assisted magnetic recording apparatus includes the above-described heat-assisted magnetic recording medium according to the first aspect, magnetic field applying means for applying a magnetic field to the heat-assisted magnetic recording medium, and locally heating the heat-assisted magnetic recording medium. Heating means.

In the first and second aspects of the present invention, preferably, the thermal conductivity of the nonmagnetic portion of the heat-assisted magnetic recording medium is 1 × 10 ² to 1 × 10 ⁵ erg / (s · cm · deg) [ Erg / (second · centimeter · temperature)]. Such a configuration is suitable for securing the heat propagation suppressing ability in the nonmagnetic portion.

  Preferably, the nonmagnetic portion of the thermally assisted magnetic recording medium is opaque. If the non-magnetic part has an excessive transparency with respect to the irradiation laser at the time of information recording, a good temperature distribution may not be formed in the recording layer at the time of information recording. An opaque nonmagnetic portion is suitable for ensuring a good heat distribution of the recording layer that is locally heated by laser irradiation during information recording and forming a good temperature distribution.

  The thickness of the recording magnetic part of the heat-assisted magnetic recording medium is preferably less than 80 μm, more preferably 70 μm or less. Such a configuration is suitable for preventing excessive heat propagation in the thickness direction of the recording layer that is locally heated during information recording.

  Preferably, in the heat-assisted magnetic recording medium, the nonmagnetic portion closer to the center of rotation is thicker. Such a configuration is suitable for setting the above-described heat propagation suppressing ability of the non-magnetic portion (the function of suppressing heat propagation to the adjacent information track) higher in the non-magnetic portion closer to the rotation center. When recording information on a heat-assisted magnetic recording medium, the closer the information track on which recording is performed to the center of rotation of the medium, the greater the thermal energy supplied per unit time to the information track or recording layer. In such a case, it is preferable that the above-described heat propagation suppression ability is set higher as the nonmagnetic portion is closer to the center of rotation.

  Preferably, in the heat-assisted magnetic recording medium, the nonmagnetic portion closer to the rotation center has a smaller thermal conductivity. Such a configuration is more suitable for setting the heat propagation suppression capability higher for a non-magnetic portion closer to the center of rotation.

  FIG. 1 shows a partial configuration of a magnetic disk device X according to the present invention. The magnetic disk device X includes a magnetic disk 10 and a recording / reproducing head 20, and is configured to be able to execute information recording and information reproduction by the heat-assisted magnetic recording method for the magnetic disk 10.

  As shown in FIGS. 2 and 3 in addition to FIG. 1, the magnetic disk 10 has a laminated structure including a disk substrate 11, a recording layer 12, and a protective layer 13, and information by a heat-assisted magnetic recording method. The magnetic recording medium can perform recording and information reproduction. FIG. 2 is a partial enlarged cross-sectional view of the magnetic disk device X, showing a predetermined radial partial cross-section of the magnetic disk 10 and a cross-section of the recording / reproducing head 20 facing the magnetic disk 10. FIG. 3 is another partial enlarged cross-sectional view of the magnetic disk device X, and shows a predetermined circumferential partial cross-section of the magnetic disk 10 and a cross-section of the recording / reproducing head 20 facing the magnetic disk 10.

  The disk substrate 11 is a part for ensuring the rigidity of the magnetic disk 10 and is made of, for example, an aluminum alloy, glass, or resin.

As shown in FIG. 2, the recording layer 12 includes a plurality of recording magnetic portions 12a and a plurality of nonmagnetic portions 12b. The plurality of recording magnetic portions 12 a are locations where information is recorded on the magnetic disk 10, and are concentrically arranged on the disk substrate 11 with the rotation center A of the magnetic disk 10 as a common center. That is, in the magnetic disk 10, an information track is set in each recording magnetic part 12a. Such a recording magnetic part 12a is made of, for example, a Co alloy, an Fe alloy, or a rare earth transition metal amorphous alloy. 2 is 140 nm or less, for example, and the thickness of the recording magnetic part 12a to the recording layer 12 is preferably 70 μm or less. The recording magnetic part 12a having a thickness of 70 μm or less is suitable for preventing excessive heat propagation in the thickness direction of the recording layer 12 that is locally heated during information recording on the magnetic disk 10 as will be described later. It is. If excessive heat propagation occurs in the thickness direction of the recording layer 12 during information recording, it becomes difficult to form a good temperature distribution in the recording layer 12. On the other hand, each nonmagnetic portion 12b is interposed between the recording magnetic portions 12a and structurally separates the adjacent recording magnetic portions 12a. That is, the plurality of nonmagnetic portions 12b are also concentrically arranged on the disk substrate 11 with the rotation center A as a common center. The thermal conductivity of the nonmagnetic portion 12b is set to 1/100 or less of the thermal conductivity of the recording magnetic portion 12a, and is, for example, 1 × 10 ² to 1 × 10 ⁵ erg / (s · cm · deg). The width W2 shown in FIG. 2 of the nonmagnetic portion 12b is, for example, 30 to 140 nm. Such a nonmagnetic portion 12b is made of, for example, SiO ₂ or SiN, and preferably a light-shielding agent is added to ensure the opacity of the nonmagnetic portion 12b.

The protective layer 13 is a part for physically and chemically protecting the recording layer 12 from the outside, and is made of, for example, SiN, SiO ₂ , or diamond-like carbon.

  In the laminated structure of the magnetic disk 10 including the disk substrate 11, the recording layer 12, and the protective layer 13, other layers may be included as necessary. Further, the magnetic disk 10 is supported by a spindle motor 31 as shown in FIG. 1, and can rotate by the spindle motor 31 being driven to rotate.

  As shown in FIG. 3, the recording / reproducing head 20 includes a slider body 21, a condenser lens 22, a recording element 23, and a reproducing element 24. Information recording and information reproduction by the magnetic disk device X are performed. Is executed to face the recording layer 12 of the magnetic disk 10.

  The slider body 21 generates a gas lubrication film between the magnetic disk 10 and the recording / reproducing head 20 when the linear velocity of the portion facing the recording / reproducing head 20 in the rotating magnetic disk 10 is equal to or higher than a predetermined value. For a predetermined shape. The condenser lens 22 is for converging the laser L emitted from a light source (not shown) on the recording layer 12 of the magnetic disk 10. The recording element 23 is for applying a predetermined recording magnetic field H to the recording layer 12, and includes a coil for flowing a current for generating a magnetic field and a magnetic pole for converting the generated magnetic field into a strong magnetic field. Become. The applied magnetic field strength and magnetic field application timing by the recording element 23 are controlled based on a predetermined control signal from a control unit (not shown). The reproducing element 24 is for detecting a magnetic signal derived from the magnetization state of the recording layer 12 and converting it into an electric signal, and is composed of, for example, a GMR element or a TMR element.

  Such a recording / reproducing head 20 is connected to a recording / reproducing head actuator (not shown) via a plate spring-like suspension arm 32 (shown in FIG. 1). This actuator has a function of controlling the radial position of the recording / reproducing head 20 with respect to the magnetic disk 10, and is constituted by, for example, a voice coil motor. The suspension arm 32 is for applying a biasing force toward the magnetic disk 10 to the recording / reproducing head 20.

  When information is recorded on the magnetic disk 10 by the magnetic disk device X, the recording / reproducing head 20 is placed above the magnetic disk 10 while the magnetic disk 10 is rotated at a predetermined constant speed. At the same time, the recording / reproducing head 20 is positioned and controlled by the recording / reproducing head actuator to an information recording execution position (a position where the recording / reproducing head 20 faces the target recording magnetic part 12a as shown in FIG. 2). In FIG. 3, the relative movement direction of the recording / reproducing head 20 with respect to the rotating magnetic disk 10 is indicated by an arrow D.

  In the heat-assisted magnetic recording, the laser L having a predetermined power focused through the condenser lens 22 of the recording / reproducing head 20 is continuously irradiated toward the recording layer 12 of the rotating magnetic disk 10. FIG. 4A shows an example of an in-plane temperature distribution generated in the recording layer 12 by laser irradiation. The temperature distribution in FIG. 4 is represented by a plurality of isotherms corresponding to higher temperatures toward the inner side. In FIG. 4, the left side is the front in the relative movement direction of the recording / reproducing head 20 with respect to the magnetic disk 10. Along with the local temperature rise of the recording layer 12 as described above, the recording element 23 mounted on the recording / reproducing head 20 applies a recording magnetic field H to the temperature rise region in the recording magnetic portion 12a of the recording layer 12. Further, by sequentially reversing the direction of the recording magnetic field H generated by the recording element 23, a plurality of magnetic domains (record marks) whose magnetization directions are sequentially reversed in the recording magnetic part 12a are arranged in the circumferential direction of the magnetic disk 10 or in the track extending direction. Form together. At this time, by controlling the timing of reversing the direction of the recording magnetic field H, a recording mark is formed with a predetermined length in each. In the magnetic disk device X, information recording is executed as described above.

In the magnetic disk 10, the information track is set in the recording magnetic part 12a as described above, and the information track T1 in the recording layer 12 that is in the process of recording information and is locally heated sequentially is adjacent to the information track T1. A nonmagnetic portion 12b having a thermal conductivity of 1/100 or less of the thermal conductivity of the information tracks T1 and T2 (recording magnetic portion 12a) is interposed between the other information tracks T2. Therefore, propagation of heat supplied to the information track T1 by laser irradiation for the purpose of increasing the temperature of the information track T1 from the information track T1 to the information track T2 is considerably suppressed. As described above, the thermal conductivity of the nonmagnetic portion 12b is preferably set to 1 × 10 ² to 1 × 10 ⁵ erg / (s · cm · deg). This is suitable for ensuring the heat propagation suppressing ability in the nonmagnetic portion 12b.

  In the magnetic disk 10, the information track T1 to which the recording magnetic field H is sequentially applied and the information track T2 adjacent to the information track T1 in the recording layer 12 at the time of information recording are adjacent to the nonmagnetic portion 12b. It is divided by. Therefore, the influence of the recording magnetic field H applied by the recording element 23 of the recording / reproducing head 20 on the information track T1 on the information track T2, and the recording mark formed on the information track T1 and the information track T2 are formed. The magnetic influence between the recorded marks is considerably reduced.

  Therefore, in the magnetic disk 10, it is possible to prevent or suppress the occurrence of the cross write phenomenon and to reduce the track pitch or increase the recording density.

  In addition, in the magnetic disk 10, for example, as described above, the heat propagation from the information track T <b> 1 to the information track T <b> 2 that is being sequentially heated locally is suppressed, as described above. A temperature distribution as shown in FIG. 4A can be generated in the recording layer 12. Specifically, in the magnetic disk 10, the temperature distribution in which the shape in each isotherm is expressed by a plurality of isotherms that are linear in both the track width direction and the track extension direction, and the temperature change is small over the entire track width. Can be generated in the recording layer 12.

  In a conventional heat-assisted magnetic recording medium, in the recording layer at the time of information recording, for example, as shown in FIG. 5A, a temperature distribution represented by a plurality of circular isotherms (corresponding to higher temperatures toward the inner side). Occurs in the recording layer (in FIG. 5, the left side is the front in the relative movement direction of the heating means with respect to the magnetic disk). When a magnetic field is sequentially applied to the information track under such temperature distribution conditions, so-called arrow-shaped recording marks M ′ are sequentially formed along the information track T ′ as shown in FIG. 5B. It is known that

  On the other hand, in the magnetic disk 10 according to the present invention, the above-described temperature distribution represented by a plurality of isotherms approximate to a rectangle can be generated in the recording layer 12 during information recording. As shown in (b), rectangular recording marks M can be sequentially formed along the information track T1. The rectangular recording mark M is more suitable for reducing the mark transition width d (the actual recording mark length in the track extending direction) than the conventional arrow feather-shaped recording mark M ′. This is suitable for improving the density (recording density in the track extending direction). Therefore, the magnetic disk 10 is suitable for increasing the recording density by reducing the recording marks.

  In the magnetic disk 10, the nonmagnetic portion 12b closer to the rotation center A may be set wider. Further, a smaller thermal conductivity may be set for the nonmagnetic portion 12b closer to the rotation center A. These configurations are suitable for setting the above-described heat propagation suppressing ability of the nonmagnetic portion 12b to be higher as the nonmagnetic portion 12b is closer to the rotation center A. When the magnetic disk 10 is rotated at a constant rotation speed during information recording in the magnetic disk device X, the closer the information track T1 to be recorded is to the rotation center A of the magnetic disk 10, the closer to the information track T1 or the recording layer 12 is. On the other hand, the thermal energy per unit time supplied by laser irradiation is large. Therefore, in this case, it is preferable that the above-described heat propagation suppression capability of the nonmagnetic portion 12b is set higher as the nonmagnetic portion 12b is closer to the rotation center A.

  Examples of the present invention will be described below together with comparative examples.

[Example 1]
With respect to the magnetic disk adopting the following specific conditions in the configuration of the magnetic disk 10 described above, information is recorded (when laser irradiation is performed) using simulation software (trade name: LASMA, manufactured by Fuji Research Institute). The temperature distribution generated in the recording layer was simulated.

The thermal conductivity of the disk substrate 11 was 1 × 10 ² erg / (s · cm · deg). The recording magnetic part 12a of the recording layer 12 had a width (information track width) of 0.14 μm, a thickness of 30 nm, and a thermal conductivity of 1 × 10 ⁶ erg / (s · cm · deg). The nonmagnetic portion 12b of the recording layer 12 has a width of 0.14 μm, which is the same as that of the recording magnetic portion 12a, a thickness of 30 nm, which is the same as that of the recording magnetic portion 12a, and a thermal conductivity of 1 × 10 ⁴ erg / (s · cm · deg). The protective layer 13 was a SiN film having a thickness of 5 μm and a thermal conductivity of 1 × 10 ² erg / (s · cm · deg). Regarding the conditions of the irradiation laser, the laser wavelength was 400 nm, the laser beam diameter was 0.2 μm, the laser power was 0.58 mW, and the laser scanning speed (circumferential speed) was 6 m / s.

  The simulation results in this example are shown in the graph of FIG. In the graph of FIG. 6, the horizontal axis represents the circumferential position in the recording layer, and the vertical axis represents the radial distance from the center position in the width direction of the recording magnetic part 12a (information track) that receives the laser irradiation. The region S1 is 20 to 40 ° C., the region S2 is 40 to 60 ° C., the region S3 is 60 to 80 ° C., the region S4 is 80 to 100 ° C., the region S5 is 100 to 120 ° C., and the region S6. Represents a temperature range of 120 to 140 ° C., a region S7 of 140 to 160 ° C., a region S8 of 160 to 180 ° C., and a region S9 of 180 to 200 ° C. Moreover, the temperature change of the location along the broken line in the graph of FIG. 6 is shown in the graph of FIG. In the graph of FIG. 10, the horizontal axis represents the relative distance from the center position in the width direction of the information track (relative distance 1 corresponds to 0.28 μm of the information track pitch), and the vertical axis represents the relative temperature (relative temperature). 1 corresponds to 200 ° C.), and the temperature change in this example is represented by line E1.

[Example 2]
In the configuration of the magnetic disk 10 described above, the thickness of the recording magnetic portion 12a and the nonmagnetic portion 12b is 80 nm instead of 30 nm, and the laser power is 1.3 mW instead of 0.58 mW for the irradiation laser conditions. Simulated the temperature distribution generated in the recording layer during information recording (laser irradiation) under the same conditions as in Example 1.

  The simulation result in this example is shown in the graph of FIG. In the graph of FIG. 7, the horizontal axis represents the circumferential position in the recording layer, and the vertical axis represents the radial distance from the center position in the width direction of the recording magnetic part 12a (information track) that receives laser irradiation, and isotherm. The region S1 is 20 to 40 ° C., the region S2 is 40 to 60 ° C., the region S3 is 60 to 80 ° C., the region S4 is 80 to 100 ° C., the region S5 is 100 to 120 ° C., and the region S6. Represents a temperature region of 120 to 140 ° C, region S7 of 140 to 160 ° C, region S8 of 160 to 180 ° C, region S9 of 180 to 200 ° C, and region S10 of 200 to 280 ° C.

[Comparative Example 1]
A recording magnetic layer (continuous film having a thickness of 30 nm) having a thermal conductivity of 1 × 10 ⁶ erg / (s · cm · deg) is set instead of the recording magnetic portion 12a and the nonmagnetic portion 12b, and the conditions of the irradiation laser The temperature distribution generated in the recording layer during information recording (laser irradiation) was simulated under the same conditions as in Example 1 except that the laser power was changed to 0.96 mW instead of 0.58 mW.

  The simulation result in this comparative example is shown in the graph of FIG. In the graph of FIG. 8, the horizontal axis represents the circumferential position in the recording layer, the vertical axis represents the radial distance from the center position in the width direction of the information track subjected to laser irradiation, and the temperature distribution represented by the isotherm. The region S4 is 80 to 100 ° C., the region S5 is 100 to 120 ° C., the region S6 is 120 to 140 ° C., the region S7 is 140 to 160 ° C., the region S8 is 160 to 180 ° C., and the region S9 is 180 to 200 ° C. Represents the temperature range. Moreover, the temperature change of the location along the broken line in the graph of FIG. 8 is shown with the line C1 in the graph of FIG.

[Comparative Example 2]
Instead of the thermal conductivity of the non-magnetic portion 12b 1 × 10 ⁴ in the configuration of the magnetic disk 10 described above erg / (s · cm · deg ) and ^{1 × 10 5 erg / (s} · cm · deg) nm, and The temperature distribution generated in the recording layer during information recording (laser irradiation) was simulated under the same conditions as in Example 1 except that the laser power was changed to 0.8 mW instead of 0.58 mW. .

  The simulation result in this comparative example was substantially the same as the simulation result in comparative example 1. That is, the temperature distribution in the recording layer of this comparative example was substantially the same as the temperature distribution in the recording layer of comparative example 1. About this comparative example, the temperature change of the location corresponded to the location along the broken line in the graph of FIG. 8 is shown by the line C2 in the graph of FIG.

[Evaluation]
As shown in FIGS. 8 and 9, in the magnetic disks of Comparative Examples 1 and 2, a temperature distribution spreading in the track crossing direction, that is, a temperature distribution in which the temperature gradient in the track crossing direction is unduly gentle occurs. In such a magnetic disk, a cross-write phenomenon in which a recording mark of an adjacent information track disappears or deteriorates easily occurs during information recording. On the other hand, as shown in FIGS. 6, 7, and 9, in the magnetic disks of Examples 1 and 2, the temperature distribution in which the spread in the track crossing direction is suppressed, that is, the temperature gradient in the track crossing direction, is shown. A steep temperature distribution occurs. Such a magnetic disk is suitable for preventing the occurrence of the cross write phenomenon, and is therefore suitable for reducing the pitch of the track or increasing the recording density.

  On the other hand, comparing the simulation results in Examples 1 and 2, it can be seen that the magnetic disk of Example 1 can form a more preferable temperature distribution with a lower laser power than the magnetic disk of Example 2. In the magnetic disk of the first embodiment, a temperature similar to that of the magnetic disk of the second embodiment is realized in the vicinity of the center in the width direction of the information track by a laser having a lower output than that required for the magnetic disk of the second embodiment. Can do. In the magnetic disk of the second embodiment, the temperature near the boundary between the recording magnetic portion 12a and the nonmagnetic portion 12b rises excessively, whereas in the magnetic disk of the first embodiment, the recording magnetic portion 12a and the nonmagnetic portion 12b. Such an excessive temperature rise does not occur in the vicinity of the boundary. Such a difference is caused by a difference in thickness of the recording magnetic part 12a in the first and second embodiments. From the simulation results of Examples 1 and 2, it can be seen that the thickness of the recording magnetic part 12a is preferably about 30 nm (Example 1) rather than 80 nm (Example 2).

  As a summary of the above, the configurations of the present invention and variations thereof are listed below as supplementary notes.

(Appendix 1) A heat-assisted magnetic recording medium having a recording layer and rotating during information recording,
The recording layer includes a plurality of recording magnetic portions extending in parallel around the rotation center of the rotating operation, and a nonmagnetic portion interposed between adjacent recording magnetic portions,
The heat-assisted magnetic recording medium, wherein the nonmagnetic portion has a thermal conductivity of 1/100 or less of the thermal conductivity of the recording magnetic portion.
(Supplementary note 2) The heat-assisted magnetic recording medium according to supplementary note 1, wherein the nonmagnetic portion has a thermal conductivity of 1 × 10 ² to 1 × 10 ⁵ erg / (s · cm · deg).
(Supplementary note 3) The heat-assisted magnetic recording medium according to supplementary note 1 or 2, wherein the nonmagnetic portion is opaque.
(Supplementary note 4) The thermally assisted magnetic recording medium according to any one of supplementary notes 1 to 3, wherein the recording magnetic portion has a thickness of 70 μm or less.
(Supplementary note 5) The heat-assisted magnetic recording medium according to any one of supplementary notes 1 to 4, wherein the nonmagnetic portion closer to the rotation center is wider.
(Supplementary note 6) The heat-assisted magnetic recording medium according to any one of supplementary notes 1 to 5, wherein the nonmagnetic portion closer to the rotation center has a smaller thermal conductivity.
(Supplementary note 7) The heat-assisted magnetic recording medium according to any one of supplementary notes 1 to 6,
A magnetic field applying means for applying a magnetic field to the heat-assisted magnetic recording medium;
A heat-assisted magnetic recording apparatus comprising: heating means for locally heating the heat-assisted magnetic recording medium.

2 shows a partial configuration of a magnetic disk device according to the present invention. FIG. 2 is a partial enlarged cross-sectional view of the magnetic disk shown in FIG. 1 and shows a predetermined radial cross section of the magnetic disk. FIG. 3 is another partial enlarged cross-sectional view of the magnetic disk shown in FIG. 1, and shows a predetermined circumferential cross section of the magnetic disk. (A) is a schematic diagram of the temperature distribution generated in the recording layer during information recording on the magnetic disk shown in FIG. 1, and (b) is a recording mark formed sequentially along the information track of the magnetic disk shown in FIG. Is schematically represented. (A) is a schematic diagram of a temperature distribution generated in a recording layer during information recording on a conventional heat-assisted magnetic disk, and (b) is a recording mark sequentially formed along information tracks on the conventional heat-assisted magnetic disk. Is schematically represented. 2 shows a temperature distribution of a recording layer in Example 1. 2 shows a temperature distribution of a recording layer in Example 2. 2 shows a temperature distribution of a recording layer in Comparative Example 1. The temperature distribution of each recording layer in Example 1 and Comparative Examples 1 and 2 is represented.

Explanation of symbols

X Magnetic disk device 10 Magnetic disk 11 Disk substrate 12 Recording layer 12a Recording magnetic part 12b Nonmagnetic part 13 Protective layer 20 Recording / reproducing head 22 Condensing lens 23 Recording element 24 Reproducing element T1, T2, T 'Information track A Rotation center L Laser H Recording magnetic field M, M 'Recording mark d Mark transition width

Claims (5)

A heat-assisted magnetic recording medium having a recording layer and rotating during information recording,
The recording layer includes a plurality of recording magnetic portions extending in parallel around the rotation center of the rotating operation, and a nonmagnetic portion interposed between adjacent recording magnetic portions,
The heat-assisted magnetic recording medium, wherein the nonmagnetic portion has a thermal conductivity of 1/100 or less of the thermal conductivity of the recording magnetic portion. ^2. The heat-assisted magnetic recording medium according to claim 1, wherein the nonmagnetic portion has a thermal conductivity of 1 × 10 ² to 1 × 10 ⁵ erg / (s · cm · deg).   The thermally assisted magnetic recording medium according to claim 1, wherein the nonmagnetic part is opaque.   The heat-assisted magnetic recording medium according to claim 1, wherein the recording magnetic part has a thickness of 70 μm or less. The heat-assisted magnetic recording medium according to any one of claims 1 to 4,
A magnetic field applying means for applying a magnetic field to the heat-assisted magnetic recording medium;
A heat-assisted magnetic recording apparatus comprising: heating means for locally heating the heat-assisted magnetic recording medium.

Images