JP2005078761A - Information reproducing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reproducing system which is suitable for reproducing recording magnetic domains that are recorded by near-field light. <P>SOLUTION: An information reproducing system is provided with an information recording medium 10 having a magnetic layer in which information is recorded as magnetic domains, a means 6 which locally heats the information recording medium 10 and a means 8 which detects magnetic field from the information recording medium 10. Magnetization of a magnetic layer 13 at the temperature, in which recorded magnetic domains formed in the magnetic layer 13 of the information recording medium 10 are to be reproduced, is set greater than the magnetization of the magnetic layer 13 in a room temperature and the means 8 which detects the magnetic field is arranged posterior to the means 6, which is used to locally heat the information recording medium 10, along the progressing direction of the medium 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an information reproducing system for reading out information from an information recording medium in which information is hybrid-recorded using near-field light.

  In recent years, a technique for recording information using near-field light has attracted attention. Since the near-field light can concentrate energy in a very small area compared to the propagation light, high-density recording that is impossible with normal propagation light irradiation is possible. That is, by recording information using near-field light, it is possible to record in a region smaller than the optical resolution determined from the wavelength of the laser light irradiated as propagating light and the numerical aperture NA of the optical system. .

  As a technique for information recording using near-field light, for example, Japanese Patent Application Laid-Open No. 2002-277376 discloses a near-field light probe and a near-field light recording / reproducing apparatus. In Japanese Patent Laid-Open No. 2002-277376, the thickness of the reflector formed around the optical probe having an aperture of a size less than the wavelength is made thin around the opening facing the information recording medium, and thickened in other regions. A heat sink structure is provided to release the heat of the reflector around the opening to the rear or side. Further, a heat radiating fin or a thermal insulator is provided around the reflective film. This prevents unnecessary melting of the information recording medium due to heating from the reflector around the probe opening during near-field optical recording, and forms a recording mark of about the opening size with high sensitivity and a wide power margin. be able to.

  Another example of an information recording medium using near-field light is disclosed in JP-A-2002-251787. An information recording medium disclosed in JP-A-2002-251787 is an optical information recording medium having at least a recording layer on a substrate, and performs recording, reproduction and erasure, or recording and reproduction with near-field light. In JP-A-2002-251787, a metal layer having a film thickness of 30 nm or less is provided between the substrate and the recording layer, or the metal layer is not provided, whereby the wear resistance of the optical information recording medium, Strength such as impact resistance is improved.

  By the way, in recent years, hybrid recording or optically assisted magnetic recording technology has attracted attention as a fusion technology of light and magnetism. For example, a technique is disclosed in which optically assisted magnetic recording is applied to a magnetic recording medium having a recording layer formed of a ferrimagnetic material whose compensation temperature is approximately room temperature (see, for example, Patent Document 1). In the magnetic recording medium of Patent Document 1, during recording, information is recorded by applying an external magnetic field in a state where a recording layer is irradiated with a light beam to raise the temperature of a predetermined recording portion to reduce the holding force. During reproduction, information is read out by irradiating a predetermined reproduction site with a light beam to increase the magnetization and detecting a leakage magnetic field from the reproduction site via a magnetic head. As a result, it is possible to reduce crosstalk and improve the S / N of the reproduction signal.

  Further, in the optically assisted magnetic recording technology, a technology for suppressing crosstalk from adjacent tracks using a heat distribution generated by irradiation of a light beam during information reproduction has been proposed (for example, see Non-Patent Document 1). . In this method, the magnetic compensation temperature is set to about 70 ° C., and when the assist light is irradiated during reproduction, the information is reproduced by adjusting the temperature of the adjacent track to be heated to the magnetic compensation temperature, Suppresses crosstalk from adjacent tracks.

  In the conventional optically assisted magnetic recording technology, for example, by using near-field light, magnetic recording of a recording magnetic domain smaller than the optical resolution determined from the wavelength of propagating light (for example, laser light) and the numerical aperture NA of the optical system is performed. It can be formed on a medium. However, when information recorded in the minute recording magnetic domain is reproduced by a magnetic head at room temperature, it is difficult to obtain a sufficient reproduction signal amplitude. As a method for solving this problem, as described in Patent Document 1, by increasing the magnetization of the reproducing portion (recording magnetic domain) by irradiating a light beam during reproduction, the leakage magnetic field from the reproducing portion is increased. The method of detecting with a magnetic head is a promising method. However, since the magnetic domain recorded by near-field light or the like has a very small size, there is a possibility that the temperature of a plurality of recording magnetic domains may be increased at the same time when a light beam of normal propagation light is irradiated. In such a case, it becomes difficult to separate the recording magnetic domains, and high density reproduction becomes difficult. In Patent Document 1 and Non-Patent Document 1, only a recording magnetic domain recorded with propagating light is mentioned, and no mention is made of a recording magnetic domain recorded with near-field light.

Japanese Patent Laid-Open No. 4-176034 (page 2-4, FIG. 1-10) Kunio Kojima, “Optical Assisted Magnetic Recording Technology”, Applied Physics, Vol. 72, No. 5, 2003, p. 592-595

  In view of such a situation, an object of the present invention is to provide an information reproducing system suitable for reproducing a minute size recording magnetic domain recorded with near-field light.

  According to an aspect of the present invention, there is provided an information reproducing system for reproducing information recorded by a hybrid recording method using near-field light, the information recording medium having a magnetic layer in which the information is recorded as a magnetic domain, And a means for locally heating the information recording medium and a means for detecting a magnetic field from the information recording medium, and the information recording medium is heated to the reproduction temperature by means for locally heating the information when reproducing the information. Then, an information reproducing system is provided in which the magnetization of the magnetic layer at the reproducing temperature is larger than the magnetization of the magnetic layer at room temperature.

  In the information reproducing system of the present invention, when reproducing information recorded by hybrid recording (optically assisted magnetic recording) using near-field light, a predetermined recording magnetic domain is locally heated by means for locally heating the information recording medium. Then, the leakage magnetic field from the heated recording magnetic domain is detected by the means for detecting the magnetic field to reproduce the information. At that time, in the information reproducing system of the present invention, since the information recording medium in which the magnetization of the recording magnetic domain at the reproducing temperature is larger than the magnetization of the recording magnetic domain at room temperature is used, the leakage magnetic field from the recording magnetic domain heated during information reproduction Will increase. Therefore, it is possible to reproduce information with higher sensitivity even with respect to a recording magnetic domain of a small size recorded using near-field light. Further, as means for locally heating the information recording medium, it is preferable to use means for heating using near-field light.

  In the information reproducing system of the present invention, the magnetic layer is preferably made of a ferrimagnetic material. The temperature for reproducing the recording magnetic domain of the magnetic layer is preferably not less than the compensation temperature of the magnetic layer, and the compensation temperature of the magnetic layer is preferably 100 ° C. or less.

  When the magnetic layer of the information recording medium is formed of a ferrimagnetic material, its coercive force and saturation magnetization temperature characteristics are, for example, as shown in FIG. In the example of FIG. 2, the compensation temperature Tcomp of the magnetic layer is near room temperature, and the reproduction temperature region is Tr in FIG. When a magnetic layer formed of such a ferrimagnetic material is locally irradiated with a light beam and heated to a reproduction temperature Tr, the saturation magnetization Ms of the magnetic layer is room temperature (near Tcomp) as shown in FIG. ) More. Thereby, the leakage magnetic field from the heated recording magnetic domain increases.

  In the information reproducing system of the present invention, it is preferable that the magnetic layer is formed of an amorphous material. In particular, the amorphous material preferably contains a 3d ferromagnetic transition metal and a 4f rare earth metal. The 3d ferromagnetic transition metal preferably contains at least one element of Co and Fe, and the 4f rare earth metal preferably contains at least one element selected from the group consisting of Tb, Gd and Dy. . For example, the material for forming the magnetic layer is preferably a rare earth-transition metal alloy such as TbFeCo, TbFe, GdFe, GdFeCo, TbCo, DyFeCo, DyFe, and DyCo, or a material obtained by adding Cr, Zr, or the like to these alloys. .

  In the information reproducing system of the present invention, it is preferable that the means for detecting the magnetic field is arranged behind the means for locally heating in the traveling direction of the information recording medium. Furthermore, in the information reproducing system of the present invention, it is preferable that the means for locally heating the information recording medium and the means for detecting the magnetic field are mounted on the slider.

  As means for detecting the magnetic field, a highly sensitive magnetic flux detection sensor such as a giant magnetoresistance effect (GMR) or a tunnel magnetoresistance effect (TMR) can be used. High-sensitivity magnetic flux detection sensors such as GMR and TMR have a multilayer thin film structure in which magnetic and non-magnetic thin films of nanometer order or less are stacked alternately, and the magnetization state of the multilayer film changes due to external magnetic flux. In response to this, the fact that the electrical resistance changes is utilized. A reproducing magnetic head using such a magnetic flux detection sensor is susceptible to heat and has a problem in temperature resistance characteristics.

  In the information reproducing system of the present invention, the means for detecting the magnetic field is disposed behind the means for locally heating in the traveling direction of the information recording medium (the direction opposite to the traveling direction of the slider). The means for detecting the magnetic field is forcibly cooled by the wind pressure generated by the progress of the medium. Therefore, even if a high-sensitivity magnetic flux detection sensor such as GMR or TMR is used as the means for detecting the magnetic field, the deterioration or the like can be prevented. On the other hand, when the means for detecting the magnetic field is disposed in front of the means for locally heating in the traveling direction of the information recording medium, the heat generated by the means for locally heating The wind pressure generated by the travel is accumulated in the means for detecting the magnetic field.

  In the information reproducing system of the present invention, information recorded as magnetic domains on an information recording medium by a hybrid recording method using near-field light is used by means for locally heating the information recording medium and means for detecting a magnetic field. Reproduce. At that time, since the information recording medium in which the magnetization of the magnetic layer at the reproducing temperature is larger than the magnetization of the magnetic layer at room temperature is used, even a minute magnetic domain recorded by near-field light is reproduced with higher sensitivity. And high-resolution reproduction is realized with near-field light.

  Further, in the information reproducing system of the present invention, the means for detecting the magnetic field is disposed behind the means for locally heating in the traveling direction of the information recording medium, so the wind pressure generated by the traveling of the information recording medium The means for detecting the magnetic field is forcibly cooled, and the deterioration of the means for detecting the magnetic field can be prevented.

  Hereinafter, embodiments of the information reproducing system of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

  A schematic diagram of the information reproducing system of this embodiment is shown in FIG. The information reproducing system of this example includes an information recording medium 10 and a recording / reproducing head 100 as shown in FIG. The recording / reproducing head 100 includes a slider 4 on which a reproducing magnetic field detecting element 8 and a recording magnetic head 9 are mounted, and an optical system such as a reflecting mirror 2 and a condenser lens 3 for guiding the light beam 1 to the slider 4. Is done.

  As shown in FIG. 1, the slider 4 is held by an arm 5 and floats on the information recording medium 10 when the information recording medium 10 moves. As shown in FIG. 1, a taper-shaped hole 7 whose cross section decreases downward is formed at the approximate center of the slider 4, and the light beam 1 is further provided at the bottom of the taper-shaped hole 7. A lens 6 (means for locally heating the information recording medium) that collects light and generates near-field light is provided. In the information reproducing system of this example, the information recording medium 10 is locally heated by the near-field light generated by the lens 6.

  Further, on the surface of the slider 4 facing the information recording medium 10, as shown in FIG. 1, a magnetic field detection element 8 (information) for detecting a leakage magnetic field from a recording magnetic domain formed on the information recording medium 10. Means for detecting a magnetic field from the recording medium) and a recording magnetic head 9 for recording information on the information recording medium 10 are provided. As the magnetic field detection element 8, a highly sensitive magnetic flux detection sensor such as GMR or TMR can be used. However, as shown in FIG. 1, the magnetic field detection element 8 is a lens for locally heating the information recording medium 10 in the traveling direction of the information recording medium 10 relative to the slider 4 (white arrow in FIG. 1). It is arranged behind 6.

  In the information reproducing system of this example, as shown in FIG. 1, the magnetic field detecting element 8 is arranged behind the lens 6 for locally heating the information recording medium 10 in the traveling direction of the information recording medium 10. Yes. Therefore, since the slider 4 travels in the direction opposite to the traveling direction of the information recording medium 10, the magnetic field detecting element 8 is forcibly cooled by the wind pressure generated by the travel of the slider 4. Therefore, even if a high-sensitivity magnetic flux detection sensor such as GMR or TMR is used for the magnetic field detection element 8, the deterioration or the like can be prevented.

  Next, the information recording medium 10 produced in this example will be described. As shown in FIG. 1, the information recording medium 10 has a structure in which a heat sink layer 12, a magnetic layer 13, and a protective layer 14 are sequentially laminated on a substrate 11.

  The magnetic layer 13 is a layer in which information is recorded as minute magnetic domains, and can be formed by a method such as sputtering or vapor deposition. In this example, a ferrimagnetic material is used as the magnetic layer 13.

  FIG. 2 shows the temperature characteristics of the coercive force Hc and the saturation magnetization Ms of the magnetic layer 13 formed using a ferrimagnetic material. FIG. 2A shows the temperature characteristic of the coercive force Hc of the magnetic layer 13, and FIG. 2B shows the temperature characteristic of the saturation magnetization Ms of the magnetic layer 13. The region Tr in FIG. 2 is a reproduction temperature region during information reproduction in the information reproduction system of this example, and the region Tw in FIG. 2 is a recording temperature region during information recording. As shown in FIG. 2, the magnetic layer 13 of the information recording medium 10 of the present invention has a magnetization characteristic having a compensation temperature Tcomp in a temperature region of 100 ° C. or lower, for example, near room temperature. At the compensation temperature Tcomp, the saturation magnetization Ms becomes 0 and the coercive force Hc diverges. In this example, a TbFeCo amorphous alloy was used as the ferrimagnetic material, and the composition was adjusted so that the compensation temperature of the magnetic layer 13 was not more than room temperature.

  In the information recording medium 10 of this example, the reproduction temperature Tr is set to be higher than the compensation temperature Tcomp of the magnetic layer and slightly lower than the temperature at which the saturation magnetization becomes maximum, as shown in FIG. The Therefore, when a predetermined recording magnetic domain is locally irradiated with a light beam or the like and heated to the reproduction temperature Tr during reproduction, the saturation magnetization of the recording magnetic domain increases. When the saturation magnetization increases, the leakage magnetic field from the recording magnetic domain also increases, so that the reproduction output obtained from the recording magnetic domain also increases. In this example, near-field light is used as a light beam for locally irradiating the recording magnetic domain, so the area to be heated becomes very small and the temperature of multiple recording magnetic domains is not increased at the same time, resulting in high resolution. Playback becomes easy. However, when the reproduction temperature Tr is set near the temperature at which the saturation magnetization becomes maximum, the saturation magnetization increases. However, as shown in FIG. 2A, the coercive force is decreased, and the magnetization of the recording magnetic domain is easily reversed. Therefore, the reproduction temperature Tr is preferably set to be slightly lower than the temperature at which the saturation magnetization is maximized. Note that the recording temperature Tw is set to a temperature higher than the reproduction temperature Tr because the coercive force Hc of the magnetic layer 13 needs to be sufficiently lowered in order to facilitate recording during information recording.

  When recording information on the information recording medium 10 produced in this example, the information recording medium 10 is locally irradiated with near-field light generated by the lens 6 provided on the slider 4 in FIG. Information was recorded by heating and applying a magnetic field to the heated area with the recording magnetic head 9. The information recorded using the near-field light is reproduced by locally irradiating the information recording medium 10 with the near-field light generated by the lens 6 so that a leakage magnetic field from the heated recording magnetic domain is detected. This was done by detecting at 8. When reproducing information, a light beam such as a laser beam can be used as the light beam 1 applied to the lens 6.

  Next, the spatial distribution of the leakage magnetic field generated from the recording magnetic domain formed in the magnetic layer 13 of the information recording medium 10 during information reproduction will be described with reference to FIGS. When the information recording medium 10 is irradiated with near-field light generated from the lens 6 provided on the slider 4 during reproduction, the temperature distribution of the magnetic layer 13 of the information recording medium 10 becomes as shown in FIG. The temperature rises as the near-field light emitting part is approached. At the time of information reproduction, the leakage magnetic field from the magnetic layer 13 is detected by the magnetic field detection element 8, and the temperature region directly below the magnetic field detection element 8 corresponds to the reproduction temperature Tr in FIG.

  The spatial distribution of the leakage magnetic field in the temperature distribution shown in FIG. 3 is shown in FIG. Here, as an example, as shown in FIG. 4, the magnetic domain 21 in which the downward magnetization is recorded, and adjacent to the rear of the magnetic domain 21 in the traveling direction of the information recording medium 10 (white arrow in FIG. 4), Consider a leakage magnetic field (thick line in FIG. 4) generated from the magnetic domain 22 in which the upward magnetization is recorded.

  When the magnetic domain 21 is located directly below the magnetic field detection element 8 (in the case of FIG. 4A), the magnetic domain 21 has the temperature distribution of FIG. 3, and the downward magnetization of the magnetic domain 21 increases toward the high temperature side. Therefore, the downward leakage magnetic field generated from the magnetic domain 21 also increases toward the high temperature side as shown in FIG. Therefore, the magnetic field detection element 8 can detect the downward leakage magnetic field of the magnetic domain 21 with higher sensitivity. On the other hand, with respect to the magnetic domain 22, the boundary region between the magnetic domain 21 and the magnetic domain 22 is slightly heated. In the vicinity, as shown in FIG. 4A, the upward leakage magnetic field is slightly increased.

  Next, when the information recording medium 10 advances until the half region on the magnetic domain 21 side of the magnetic domain 22 is located directly below the magnetic field detection element 8, the spatial distribution of the leakage magnetic field below the magnetic field detection element 8 is as shown in FIG. It becomes like this. In this case, since the half region on the magnetic domain 21 side of the magnetic domain 22 has a temperature distribution as shown in FIG. 3, the upward magnetization increases toward the high temperature side in the half region on the magnetic domain 21 side of the magnetic domain 22. The upward leakage magnetic field also increases toward the high temperature side as shown in FIG. Therefore, in the state of FIG. 4B, the magnetic field detection element 8 can detect the upward leakage magnetic field of the magnetic domain 22 with higher sensitivity.

  Furthermore, when the information recording medium 10 advances and the half region opposite to the magnetic domain 21 of the magnetic domain 22 is located directly below the magnetic field detection element 8, the spatial distribution of the leakage magnetic field below the magnetic field detection element 8 is as shown in FIG. It changes as shown in (c).

  In the above embodiment, near-field light is generated using the lens 6 in FIG. 1 during information reproduction, but the present invention is not limited to this. For example, near-field light may be generated using a near-field optical probe, SIL, bowtie antenna, optical waveguide, or the like.

In the information reproducing system of the present invention, when information is reproduced, the recording magnetic domain formed in the magnetic layer of the information recording medium is locally heated so that the leakage magnetic field from the recording magnetic domain can be increased and detected. High resolution playback is possible. In the information reproducing system of the present invention, the magnetic field detecting means is arranged behind the locally heating means in the traveling direction of the information recording medium, so that the magnetic field is detected by the wind pressure generated by the traveling of the information recording medium. The means for forcibly cooling is able to prevent deterioration of the means for detecting the magnetic field. Therefore, in the information reproduction system of the present invention, an information reproduction system that reproduces information while heating an information recording medium that has been recorded with ultra-high density (for example, several hundred Gbits / inch ² or more) using near-field light or the like. A suitable system can be provided.

It is a schematic block diagram of the information reproduction | regeneration system of an Example. It is the figure which showed the magnetization characteristic of the magnetic layer of an Example, Fig.2 (a) is a temperature characteristic of a coercive force, FIG.2 (b) is a temperature characteristic of saturation magnetization. It is the figure which showed the temperature distribution of the magnetic field detection element vicinity at the time of reproduction | regeneration. FIG. 4A is a diagram showing the spatial distribution of the leakage magnetic field in the vicinity of the magnetic field detection element, and FIG. 4A is the distribution of the leakage magnetic field when the magnetic domain 21 is located directly below the magnetic field detection element 8, and FIG. 4 is a distribution of the leakage magnetic field when the half region of the magnetic domain 22 on the magnetic domain 21 side is located directly below the magnetic field detection element 8, and FIG. 4C shows the half region of the magnetic domain 22 on the side opposite to the magnetic domain 21. This is the distribution of the leakage magnetic field when it is located directly below the magnetic field detection element 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light beam 4 Slider 6 Lens 8 Magnetic field detection element 9 Recording magnetic head 10 Information recording medium 13 Magnetic layers 21 and 22 Recording magnetic domain 100 Recording / reproducing head

Claims (10)

An information reproduction system for reproducing information recorded by a hybrid recording method using near-field light,
An information recording medium having a magnetic layer in which the information is recorded as magnetic domains;
Means for locally heating the information recording medium;
Means for detecting a magnetic field from the information recording medium,
When the information recording medium is heated to the reproduction temperature by the means for locally heating the information, the magnetization of the magnetic layer at the reproduction temperature is larger than the magnetization of the magnetic layer at room temperature. Information reproduction system. 2. The information reproducing system according to claim 1, wherein the magnetic layer is made of a ferrimagnetic material. 3. The information reproduction system according to claim 2, wherein the reproduction temperature is equal to or higher than the compensation temperature of the magnetic layer. The information reproducing system according to any one of claims 2 to 3, wherein the compensation temperature of the magnetic layer is 100 ° C or lower. The information reproducing system according to any one of claims 2 to 4, wherein the magnetic layer is formed of an amorphous material. 6. The information reproducing system according to claim 5, wherein the amorphous material includes a 3d ferromagnetic transition metal and a 4f rare earth metal. 7. The information reproducing system according to claim 6, wherein the 3d ferromagnetic transition metal contains at least one element of Co and Fe. The information reproduction system according to claim 6, wherein the 4f rare earth metal contains at least one element selected from the group consisting of Tb, Gd, and Dy. The information according to any one of claims 1 to 8, wherein the means for detecting the magnetic field is arranged behind the means for locally heating in the traveling direction of the information recording medium. Playback system. The information reproduction system according to claim 1, wherein the reproduction temperature is lower than a temperature at which saturation magnetization of the magnetic layer is maximized.

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