JP2001155390A - Method for reproducing information and device for recording and reproducing information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording medium and an information recording device of high performance by providing a method for forming a minute magnetic region and a method for reproducing the formed magnetic region with high sensitivity. SOLUTION: In the information recording device having at least a very minute light source and the information recording medium for recording information, an information recording medium surface is irradiated with light emitted from the very minute light source, frequency (or wavelength) or light intensity is modulated by optical interaction between the light before irradiating the information recording medium surface and the light after reflection on the medium surface and thereby resonance state of a laser light source is changed. The purpose is realized by using a reproducing system in which information recorded on the information recording medium is reproduced by detecting change of the resonance state of the laser light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording apparatus for storing a large amount of information quickly and accurately, and more particularly to an information recording apparatus suitable for high-density information recording with high performance and high reliability. It relates to the reproduction method.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in the advanced information society, and multimedia in which various forms of information are integrated has rapidly spread. There are a magnetic disk device and an optical disk device as information recording devices supporting this.
These devices are used in fields that take advantage of their respective characteristics.

[0003] At present, the magnetic disk drive is being downsized while improving the recording density. In parallel,
The cost reduction of disk devices is rapidly progressing. By the way, in order to realize high density of magnetic disk,
1) Reducing the distance between the disk and the magnetic head 2)
Indispensable techniques include increasing the coercive force of the medium and 3) devising a signal processing method. Above all, in a magnetic recording medium, an increase in coercive force is indispensable for realizing high-density recording. In addition, in order to achieve high-density recording exceeding 40 Gb / in ² , the unit in which magnetization reversal occurs must be reduced. For that purpose, it is necessary to reduce the size of the magnetic particles, and as a method for achieving this, it has been proposed to provide a seed layer below the magnetic film. One example is USP-4652499.

On the other hand, in an optical disk device that performs recording, reproduction, or erasing using a laser beam, it is effective to form a minute magnetic domain using a laser beam having a short wavelength in order to perform high-density recording. In this case, the wavelength of the laser beam becomes shorter, and the Kerr effect exhibited by the amorphous alloy of the rare earth element and the iron group element, which is the recording medium, decreases, so that the reproduction output-to-noise ratio (S / N) decreases. In some cases, stable information recording cannot be performed. To solve this problem, P that exhibits a large Kerr effect even in the short wavelength region of 400 nm or less
An artificial lattice film in which t and Co are alternately stacked has been proposed.
As an example, JP-A-1-251356 can be mentioned.
In addition, a recording method using a lens having a large aperture ratio has been proposed. Further, in the reproducing method, a reproducing method using a magnetic super-resolution method (MSR) has been proposed in addition to the reproducing method using the short wavelength light. In addition, there has been proposed a magnetic domain enlarging method in which a magnetic domain formed at the time of reproduction is enlarged to increase a reproduction signal.

[0005]

In the above prior art,
First, in a magnetic disk, there is a limit in controlling the crystal grain size distribution of an information recording magnetic film by a seed layer, and fine particles and coarse particles may coexist. These fine particles and coarse particles are
When recording information (when reversing the magnetization), it is affected by the leakage magnetic field from the surrounding magnetic particles, and conversely, for large particles, it has an ultra-high density exceeding 40 Gb / inch ² to give an interaction. When performing recording, there were cases where stable recording could not be performed. This tendency is the same in a Co—Cr-based magnetic film for perpendicular magnetic recording.

On the other hand, in the magneto-optical recording, when an artificial lattice film in which Pt and Co are alternately laminated is used as a recording film, a large Kerr rotation angle can be obtained in a short wavelength region of 400 nm or less.
The moving speed of the domain wall is high, and particularly when performing mark length recording, it causes jitter, and stable recording and reproduction cannot be performed. Further, although minute recording is possible, the resolution can be improved by the MSR method, but it is sometimes difficult to improve the reproduction signal output. In the magnetic domain expansion reproduction technology, the reproduction output can be increased by enlarging the magnetic domain at the time of reproduction.
The miniaturization of the magnetic domain size has rapidly progressed, and further improvement in the reproduction sensitivity has been desired.

Therefore, a first object of the present invention is to provide a method for reproducing a minute magnetic domain with high sensitivity. A second object of the present invention is to provide a high-performance information recording medium and an information recording device by providing a method for forming a minute magnetic domain and a method for reproducing the formed magnetic domain with high sensitivity. As described above, an object of the present invention is to provide an information reproducing method and an information recording medium suitable for performing ultra-high-density recording exceeding 40 Gb / inch ² and an information recording apparatus using them.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an information recording apparatus having at least an extremely small light source and an information recording medium for recording information, wherein a semiconductor laser is used as a light source and the semiconductor laser is in the optical path. This light is applied to the surface of the information recording medium using a very small light source provided with a slit with a minute pinhole formed therein, and the light reflected on the medium surface is taken back to the semiconductor laser element as light, By modulating the frequency (or wavelength) or light intensity of the light by the optical interaction that occurs between the light before irradiation and changing the resonance state of the semiconductor laser and detecting it as an electric signal, This can be realized by using a method of reproducing information recorded on an information recording medium. Here, the modulation of the reflected light from the recording medium is caused by the magneto-optical effect of the information recording medium. It is preferable that the magneto-optical effect referred to here is the Kerr effect and / or the Faraday effect.

As the information recording medium, it is most preferable to use a material having perpendicular magnetic anisotropy and a magneto-optical effect, and more specifically, to use an amorphous alloy of a rare earth element and an iron group element. It is. In addition to being a single magnetic layer, it is more preferable that the medium is composed of a plurality of magnetic layers with the preceding magnetic layer interposed therebetween. In this case, one of them is a recording layer for recording information, and the other magnetic layer is a magnetic domain recorded on the recording layer at the time of reproduction is transferred to the reproducing layer, and the magnetic domain is a magnetic domain larger than the recording layer. It is particularly preferable to reproduce information by using Further, of the magnetic layers, the magnetic layer on the reproduction light irradiation side induces perpendicular magnetic anisotropy by applying light irradiation and / or a magnetic field. The above-mentioned amorphous alloy of a rare earth element and an iron group element is used as a rare earth element as Tb, G
d, at least one element selected from Ho.Dy,
At least selectable from Fe, Co, and Ni as iron group elements
Most preferably, it is composed of one kind of element. Also,
As the nonmagnetic material, an oxide or nitride of silicon, tantalum, aluminum, titanium, or chromium is used.
Further, as a very small light source, it is most effective that a minute pinhole is provided in the course of the light source, and the diameter of the pinhole is 300 nm or less.

[0010] By the way, considering the whole process from recording to reproduction of information, at least an information recording medium formed on a circular substrate, a laser light source narrowed down to a certain spot size by a lens, a micro light source, and a magnetic field are applied. Using an information recording device equipped with an electromagnet, a disk drive system, and an electric circuit, as a recording / reproducing method, a laser light source and a magnetic field narrowed down to a certain spot size by at least a lens in order to record information on a magnetic recording medium. The information is reproduced using an electromagnet for applying the information, and the reproduction of information is performed using an extremely small light source. Alternatively, reproduction of information from a magnetic recording medium is performed using an extremely small light source and an electromagnet for applying a magnetic field. Such a magnetic domain is formed using at least a laser light source and a magnetic head. In this case, at least the magnetic domain formed by performing recording using the laser light source and the magnetic head has a width of the magnetic domain measured in a direction in which the information recording medium moves, the width being shorter than the magnetic gap length in the magnetic head. It is unique. More preferably, the size of the magnetic domain of the information recorded on the recording layer of the information recording medium is most preferably 0.1 μm or less as measured in the direction in which the information recording medium moves.
It is most preferable to record, reproduce, or erase various types of information using an information recording medium, an information reproducing method, and an information recording device. In particular, it is preferable that the information to be recorded or reproduced is at least one of audio information, code data, image information, and control information for controlling the magnetic disk device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to embodiments.

(Embodiment 1) In this embodiment, an information recording apparatus is constructed by using one magnetic film as an information recording layer. FIG. 1 shows a schematic diagram of a cross-sectional structure of the manufactured disk. First, a 3.5 ″ diameter glass substrate was used as the disk substrate (1). The substrate used here is only one example, and any size disk substrate can be used.
It goes without saying that the effects of the present invention are not affected even if a resin such as polycarbonate or amorphous polyolefin is used. Further, it is needless to say that a substrate having an uneven guide groove may be used for positioning the magnetic head or the optical head, or the uneven guide groove may be formed after forming the information recording medium.

On this substrate (1), Al-T is used as a light reflecting film (2).
An i film was formed to a thickness of 30 nm. Pure Ar as discharge gas, Al ₉₀ T
the i ₁₀ alloy was used, respectively to the target. The pressure during sputtering is 15 mTorr, and the input RF power is 0.5 kW / 150 mmφ.
Here, no difference was found between the composition of the obtained thin film and the composition of the target. Next, a silicon nitride film was formed by a sputtering method as the inorganic compound thin film (3). Ar / N ₂ was used for the discharge gas, with Si as the target.
The pressure during sputtering is 10mTorr, and the input RF power is 0.7kW / 150mm
φ. The thickness of the formed inorganic compound thin film is 15 nm. On this film, a Tb-Fe-Co film was formed as a magnetic film (4) to a thickness of 25 nm by a sputtering method. Tb prepared by hot static pressure press (HIP) method as a target for sputtering
_{A 26} Fe ₆₂ Co ₁₂ alloy was used, the pressure during sputtering was 5 mTorr, and the input RF power was 1.5 kW / 150 mmφ. Here, when the target is manufactured by the HIP method, it has an effect that the oxygen content in the target can be reduced and the composition difference between the target and the film can be significantly reduced. Finally, the inorganic compound thin film
As (3), a silicon nitride film is 65 nm thick by sputtering.
Was formed to a film thickness of Ar / O ₂ was used for the discharge gas, with Si as the target. The pressure during sputtering is 10mTorr,
The input RF power is 0.7kW / 150mmφ. Here, the thickness of the formed inorganic compound thin film is determined by the wavelength of light used for reproduction.

Next, the magnetic properties of the magnetic film were measured.
The obtained magnetic properties are as follows: coercive force is 10.0 kOe, perpendicular magnetic anisotropy energy is 5 × 10 ⁷ erg / ml, saturation magnetization is 120 emu
/ ml, the Kerr rotation angle was 0.89 °. The Curie temperature is 210 ° C and the compensation temperature is 80 ° C.

The reproduction characteristics of the disk using the magnetic film having the above magnetic characteristics were evaluated. FIG. 2 shows an outline of the apparatus used for the evaluation. As the information recording medium (103), a medium in which a magnetic domain having a width of 0.30 μm in the track direction and 0.5 μm in the direction perpendicular to the track was formed in advance was used. For reproduction, a semiconductor laser light (100) having a wavelength of 680 nm was used, and the light was irradiated to the information recording medium (103) through a slit (101) having a pinhole (102) having a diameter of 200 nm. When the light reflected back from the information recording medium returns to the light source, the resonance state of the laser light source changes. Since this change changes depending on the direction of magnetization of the magnetic layer, information can be reproduced. By using this method, magnetic domains with a width in the track direction of 0.3 μm to 0.2 μm (0.4
μm) was successfully reproduced. When the reproduction signal output was measured, it was C / N = 55 to 58 dB.

In this embodiment, the case where the Tb-Fe-Co system is used for the information recording film has been described, but in addition to this material system, Dy-Fe-Co, Ho-
Fe-Co, Gd-Tb-Fe-Co, Gd-Dy-Fe-Co, Gd-Ho-Fe-Co, Tb-Dy-Fe
Similar effects can be obtained by using -Co, Tb-Ho-Fe-Co, or Dy-Ho-Fe-Co. In particular, in a system containing Gd, the perpendicular magnetic anisotropy is reduced, but a large magneto-optical effect is obtained. Here, in a system containing two or more kinds of rare earth elements, the composition of the rare earth element is determined by the total amount without depending on the kind of the element. Also,
It goes without saying that the same effect can be obtained even if a part of Fe is replaced with Ni.

(Embodiment 2) The information recording medium (103) of Embodiment 1
And a magnetic field modulation recording method in which continuous light is irradiated from an optical head and information is recorded by applying a magnetic field by a flying magnetic head (110) at the same time. FIG. 3 shows a schematic diagram of the magnetic field recording method used. Here, a very small light source for reproduction may be attached to the flying magnetic head. Recording was performed on the information recording film (103) using the flying magnetic head (110). At the same time, laser light (continuous light) focused to 0.6 μm with a lens was irradiated. Here, a pulse light of about 20 ns to 60 ns may be used. In this case, the area where the temperature rises effectively becomes narrow, which is suitable for high-density recording. The formed magnetic domain had a width measured in the track direction of about 0.15 μm. The width, measured perpendicular to the track, was 0.7 μm.
When the magnetic domains formed on this information recording medium were reproduced using the ultra-small light source system shown in FIG. 2 as in Example 1, good reproduction was possible. When the playback signal output was measured, C / N = 54
dB. The S / N was found to be 34 dB. As described above, it was found that information recorded by using an extremely small light source can be favorably reproduced.

(Embodiment 3) In this embodiment, recording is performed on the information recording medium of the previous embodiment 1 by using both a thin film magnetic head and a laser light source. This is the case where an extremely small light source is used. FIG. 4 shows an outline of the recording system. The magnetic head used for recording is attached to a support spring (202). FIG. 5 shows the details of the recording head used. For recording, a thin-film magnetic head using a soft magnetic film having a high saturation magnetic flux density of 2.1 T for the magnetic core (302) was used. The distance (flying distance) between the head surface and the magnetic recording medium is 12 nm, and the gap width (301) is 0.20 μm. At the time of recording, a magnetic field is applied from this thin-film magnetic head and the laser light source (111)
, A pulse light was applied through a lens (112). The pulse width to be applied varies depending on the width of the magnetic domain to be formed. Here, a laser pulse of 40 ns was applied. According to the magnetic domain observation, the width of the formed magnetic domain is 0.
It was 1 μm. As described above, it was found that a magnetic domain narrower than the gap width of the magnetic head can be formed by using the magnetic head and the laser light source together for recording.

Next, a signal (700 kFCI) corresponding to 40 Gb / inch ² was recorded on this disk. When the recorded signal was reproduced, the S / N was 30 dB. When the defect rate of this disk was measured, the value was 1 × 10 ⁻⁵ or less when no signal processing was performed.

(Embodiment 4) In this embodiment, an information recording medium of a type in which magnetic domains recorded during reproduction are enlarged is used. FIG. 6 shows the structure of the manufactured information recording medium. A 3.5 ″ diameter glass substrate was used as the disk substrate (1). The substrate used here is only one example, and 2.
It goes without saying that the effect of the present invention is not affected by using a disk substrate of any size such as 5 ″ or by using a resin such as polycarbonate or amorphous polyolefin. Needless to say, a substrate having an uneven guide groove may be used for the positioning, or the uneven guide groove may be formed after forming the information recording medium.

On this substrate (1), an Al-T
An i film was formed to a thickness of 30 nm. Pure Ar as discharge gas, Al ₉₀ T
the i ₁₀ alloy was used, respectively to the target. The pressure during sputtering is 15 mTorr, and the input RF power is 0.5 kW / 150 mmφ.
Here, no difference was found between the composition of the obtained thin film and the composition of the target. Next, a silicon nitride film was formed by a sputtering method as the inorganic compound thin film (3). Ar / N ₂ was used for the discharge gas, with Si as the target.
The pressure during sputtering is 10mTorr, and the input RF power is 0.7kW / 150mm
φ. The thickness of the formed inorganic compound thin film is 15 nm. Next, a magnetic film composed of two layers was formed via a nonmagnetic layer. As the magnetic film I (5), a Tb-Fe-Co film was formed to a thickness of 100 nm by a sputtering method. Tb ₂₆ Fe ₆₂ Co prepared by hot static pressure press (HIP) was used as a sputtering target.
_{Using 12} alloy, the pressure during sputtering is 5 mTorr, and the input RF power is 1.5 kW / 150 mmφ. Here, when the target is manufactured by the HIP method, the oxygen content in the target can be reduced, and at the same time, the composition difference between the target and the film can be significantly reduced. On this, a non-magnetic layer (6)
A silicon nitride film was formed to a thickness of 10 nm. Ar / N ₂ was used for the discharge gas, with Si as the target. The pressure during sputtering is 10mTorr and the input RF power is 0.7kW / 150mmφ
It is. Subsequently, a Gd-Fe-Co film was formed as a magnetic layer II (7) by a sputtering method. A Gd _{2 6} Fe ₆₄ Co ₁₀ alloy produced by a hot static pressure press (HIP) method was used as a sputtering target, and Ar was used as a discharge gas. The sputtering conditions were as follows: the sputtering pressure was 5 mTorr, and the input RF power was 1.5 kW / 15
0 mmφ. The thickness of the magnetic layer II is 20 nm. As described above, when the magnetic film was formed via the nonmagnetic layer, the magnetic layers were magnetostatically coupled to each other. Finally, the inorganic compound thin film
As (3), a silicon nitride film was formed to a thickness of 65 nm by a sputtering method. Ar / O ₂ was used for the discharge gas, with Si as the target. The pressure during sputtering is 10 mTorr, and the input RF power is 0.7 kW / 150 mmφ. Here, the thickness of the formed inorganic compound thin film is determined by the wavelength of light used for reproduction.

An 800 kFCI signal was recorded on the above disk using a laser light source (optical head) and an electromagnet. Here, recording is performed by raising the magnetic layer I and the magnetic layer II to the Curie temperature and applying a magnetic field from the outside in the process of cooling the portions to direct the magnetization in a desired direction. The recorded information is stored in the magnetic layer I. At the time of reproduction, an extremely small light source and a magnetic head are used. When a magnetic field is applied from the outside by the magnetic head, the information of the magnetic layer I is transferred to the magnetic layer I.
It is enlarged and transcribed to I. This information was reproduced using laser light from a very small light source. A part of the light coming out of the pinhole is fractionated and used as a reference light, and the light reflected from the information recording medium and returned returns an optical interaction between the light from the light source, Thereby, information is reproduced by detecting that the resonance state of the semiconductor laser changes. When the reproduced signal output was measured by using this method, the C / N was 53 to 56 dB.

(Embodiment 5) In this embodiment, using the information recording medium of Embodiment 4, continuous light is irradiated from an optical head, and at the same time, information is recorded by applying a magnetic field by a floating magnetic head. This is a case where a magnetic field modulation recording method is used. The schematic diagram is as shown in FIG. Here, it goes without saying that an extremely small light source for reproduction may be attached to the flying magnetic head. First, recording was performed on the information recording film using a flying magnetic head. The formed magnetic domain was about 0.1 μm. When the magnetic domains formed on this information recording medium were reproduced using the same microscopic light source system as in Example 4, good reproduction was possible. When the reproduced signal output was measured, it was C / N = 56 dB. When the S / N was determined, it was 35 dB. As described above, it was found that information recorded by using an extremely small light source can be favorably reproduced.

(Embodiment 6) In this embodiment, recording is performed on the information recording medium of the previous embodiment 4 by using both a thin-film magnetic head and a laser light source. This is the case where an extremely small light source is used. FIG. 4 shows an outline of the recording system. For recording, a thin-film magnetic head using a soft magnetic film having a high saturation magnetic flux density of 2.1 T was used. The distance (flying distance) between the head surface and the magnetic recording medium is 12 nm, and the gap width is 0.20
μm. At the time of recording, a magnetic field was applied from the thin-film magnetic head and pulse light was applied from a laser light source. The pulse width to be applied varies depending on the width of the magnetic domain to be formed. Here, a laser pulse of 40 ns was applied.
According to the magnetic domain observation, the width of the formed magnetic domain was 0.1 μm as measured in the track direction. As described above, it was found that a magnetic domain narrower than the gap width of the magnetic head can be formed by using the magnetic head and the laser light source together for recording.

Next, a signal (700 kFCI) corresponding to 40 Gb / inch ² was recorded on this disk. When the recorded signal was reproduced, the S / N was 35 dB. When the defect rate of this disk was measured, the value was 1 × 10 ⁻⁵ or less when no signal processing was performed. Here, for comparison, when reproduction was performed using the optical head used for recording, S /
N was 28 dB. Thus, the S / N was low. this is,
This was due to low reproduction sensitivity. Further, in this case, the crosstalk was large and the resolution was low. The reason may be that the light spot cannot be made small and that the temperature of the information recording medium increases due to light irradiation. Conversely, this is a feature of the present invention.

[0026]

According to the present invention, a laser beam (extremely small light source) passing through a slit of 300 nm or less is used as a light source for reproduction,
Due to the optical interference between the polarized light on the surface of the information recording medium having a magneto-optical effect and the light from the light source, the frequency of the light
(Or wavelength) and a change in light intensity, which are detected as a change in the resonance state of the laser light source, can be reproduced. According to this method, a large light reproduction output can be obtained even for a minute magnetic domain of about 0.1 μm or less. As a result, it was possible to provide a reproducing method capable of reproducing data with good resolution and sensitivity even with a domain size of 0.1 μm or less. In particular, when the magnetic domain expansion reproducing method is used as a reproducing method for a magneto-optical disk, the effect obtained is large.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an information recording medium.

FIG. 2 is a diagram showing an information reproducing method using a minute light source.

FIG. 3 is a diagram showing an information recording method using a flying magnetic head.

FIG. 4 is a diagram showing an information recording method in which a magnetic head and an optical head are combined.

FIG. 5 is a diagram showing a structure of a thin-film magnetic head.

FIG. 6 is a schematic diagram showing a cross-sectional structure of an information recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Light reflection film 3 ... Inorganic compound film 4 ... Magnetic film 5 ... Magnetic layer I 6 ... Non-magnetic layer 7 ... Magnetic layer II 100 ... Laser light source 101 ... Slit 102 ... Pinhole 103 ... Information recording medium 110 ... Floating magnetic head 111… Laser beam 112… Lens 201… Magnetic head 202… Support spring 301… Magnetic gap 302… Magnetic core 303… Insulator 304… Current terminal 305… Thin film coil

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Teruaki Takeuchi 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Koichiro Wakabayashi 1-1-88 Ushitora, Ibaraki City, Osaka Hitachi Maxell Co., Ltd. F term (reference) 5D075 AA03 BB05 BB06 BB08 CC11 CD06 EE03 FF04 FF12 5D119 AA12 BA01 BB05 FA05 FA28

Claims (12)

[Claims] 1. An information reproducing method for reproducing an information recording medium using a very small light source, wherein the very small light source comprises:
A semiconductor package having at least a slit having a pinhole having a diameter of 50 nm or more and 300 nm or less provided in the course of a semiconductor laser and a laser beam emitted from the semiconductor laser, and transmitting the light emitted from the pinhole to the information recording medium. The light emitted to the surface of the information recording medium is reflected by the surface of the information recording medium, and the light reflected from the medium is taken back to the semiconductor laser element as light, and optical light generated between the reflected light and the light before reflection. An information reproducing method, wherein information is reproduced from the information recording medium by performing modulation by a simple interaction and detecting the degree of modulation. 2. The information reproducing method according to claim 1, wherein the modulated optical interaction is at least one selected from a frequency, a wavelength, and a light intensity. 3. The information reproducing method according to claim 1, wherein the modulated optical interaction occurs due to a magneto-optical effect of the information recording medium. 4. The information reproducing method according to claim 1, wherein a width of the recording mark measured in a moving direction of the information recording medium is smaller than a diameter of the pinhole. 5. The information reproducing method according to claim 1, wherein the information recording medium has a magnetic layer made of a material having perpendicular magnetic anisotropy and having a magneto-optical effect. 6. The information reproducing method according to claim 5, wherein said magnetic layer is an amorphous alloy of a rare earth element and an iron group element. 7. The magnetic layer transfers a magnetic domain recorded on the recording layer during reproduction via the recording layer for recording information and the recording layer and the non-magnetic layer, and the magnetic domain is shifted from the recording layer. 7. The information reproducing method according to claim 6, comprising a plurality of magnetic layers including at least a reproducing layer that forms a large magnetic domain. 8. The information reproducing method according to claim 7, wherein a perpendicular magnetic anisotropy is induced in the reproducing layer by light irradiation and / or application of a magnetic field. 9. The polarization plane is rotated by the Kerr effect and / or the Faraday effect when the light applied to the reproduction layer from the extremely small light source is reflected by the reproduction layer. Information reproduction method described. 10. A laser light source, a lens for narrowing laser light emitted from the laser light source to a fixed spot size, a magnetic head for applying a magnetic field, and a disk drive for rotating an information recording medium. An information recording / reproducing apparatus comprising at least a unit and an electric circuit, characterized in that a slit having a pinhole having a diameter of 50 nm or more and 300 nm or less is provided on the way of laser light emitted from the laser light source. 11. The information recording / reproducing apparatus according to claim 10, wherein the electric circuit includes a circuit for converting a change in the resonance state of the laser into an electric signal and detecting the electric signal as a reproduced signal. 12. The information recording method according to claim 1, wherein the information recorded on the information recording medium is at least one of audio information, code data, image information, and control information for controlling a magnetic disk drive. apparatus.