JP3515411B2 - Magneto-optical recording medium playback device - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for reproducing a signal by applying a magnetic field and irradiating a laser beam.

2. Description of the Related Art Magneto-optical recording media have been attracting attention as rewritable recording media having a large storage capacity and high reliability, and are being put to practical use as computer memories and the like. In addition, recently, the recording capacity is 6.1 Gby.
The tes magneto-optical recording medium has been standardized and is about to be put to practical use. In addition, a magnetic domain expansion reproducing technique has been developed in which an alternating magnetic field is applied in reproducing a signal from a magneto-optical recording medium, and the magnetic domain transferred from the reproducing layer to the recording layer is expanded by the alternating magnetic field to reproduce a signal. A magneto-optical recording medium capable of recording and / or reproducing a signal of 14 Gbytes by using is also proposed.

However, a magneto-optical recording medium which reproduces a signal by expanding magnetic domains generally has a sectional structure as shown in FIG. That is, the magneto-optical recording medium 200
Includes a reproduction layer 3, a nonmagnetic layer 4 formed in contact with the reproduction layer 3, and a recording layer 7 formed in contact with the nonmagnetic layer 4. When the recording density is improved and the magnetic domains formed in the recording layer 7 become minute, as shown in FIG. 9, when the laser beam LB is irradiated, the regions of the two magnetic domains 701 and 702 in the recording layer 7 are predetermined. When the temperature becomes higher than the temperature, the reproducing layer 3 passes through the non-magnetic layer 4.
Two magnetic domains 301 and 302 are transferred. Then, in the beam diameter of the laser beam LB, two magnetic domains 301,
Since the magnetic domains 301 and 302 cannot be detected independently, there is a problem that the conventional magneto-optical recording medium cannot accurately reproduce signals by expanding the magnetic domains. Therefore,
An object of the present invention is to provide a reproducing apparatus for a magneto-optical recording medium which solves such a problem and which can separately reproduce each magnetic domain of the recording layer to the reproducing layer with high resolution to reproduce a signal by expanding the magnetic domain. To do.

Means for Solving the Problems and Effects of the Invention The invention according to claim 1 is to provide a reproducing layer, a nonmagnetic layer formed in contact with the reproducing layer, and a perpendicular magnetization film formed in contact with the nonmagnetic layer. And a second intermediate magnetic layer formed in contact with the first intermediate magnetic layer, the in-plane magnetization film becoming a perpendicular magnetization film at a predetermined temperature or higher, and the second intermediate magnetic layer. In a reproducing device for reproducing a magneto-optical recording medium including a recording layer formed in contact with the layer, the application time of the first intermediate magnetic layer in the direction of the initialization magnetization is longer than the application time in the direction opposite to the initialization magnetization. , A magnetic head for applying an alternating magnetic field having a peak magnetic field larger than the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer to the magneto-optical recording medium, and an optical for irradiating the magneto-optical recording medium with laser light. A reproducing apparatus for a magneto-optical recording medium including a head. In the reproducing apparatus for a magneto-optical recording medium according to claim 1, when an alternating magnetic field is applied from the magnetic head to the magneto-optical recording medium and the magneto-optical recording medium is irradiated with laser light from the optical head, the second intermediate magnetic field is generated. A region of the layer above a predetermined temperature is changed from an in-plane magnetization film to a perpendicular magnetization film and exchange-coupled with a magnetic domain of the recording layer, and a region below a predetermined temperature retains in-plane magnetization and exchange-coupling with the magnetic domain of the recording layer. do not do. And the first
Of the intermediate magnetic layer above a predetermined temperature, all the regions weaker than the peak magnetic field of the alternating magnetic field to which the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer is applied. In a region having the same magnetization as the direction and stronger than the peak magnetic field of the alternating magnetic field to which the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer is applied, the magnetization is not reversed by the alternating magnetic field,
It is transferred to the reproducing layer by magnetostatic coupling through the non-magnetic layer.
Then, the magnetic domain transferred to the reproducing layer is detected by the laser beam as the magnetic domain is expanded by the applied alternating magnetic field.
In this case, since the application time in the direction of the initialization magnetization of the first intermediate magnetic layer is longer than the application time in the direction opposite to the initialization magnetization,
The magnetic domain of the recording layer having the magnetization in the direction opposite to the initialization magnetization is
After being transferred to the reproducing layer, the magnetic domain is expanded, and the magnetization in a region weaker than the peak magnetic field of the alternating magnetic field to which the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer is applied is changed by the alternating magnetic field. However, since it is not a change in the magnetization that reflects the magnetization of the recording layer, it does not affect the detection of the magnetic domain expanded in the reproducing layer. Therefore, according to the first aspect of the present invention, the low temperature region and the high temperature region within the spot diameter of the laser beam applied to the magneto-optical recording medium are masked to make the magnetic domain of the recording layer a high density reproducing layer. The transferred magnetic domain can be detected by expanding it with an alternating magnetic field. According to a second aspect of the invention, there is provided a reproducing layer, a non-magnetic layer formed in contact with the reproducing layer, a first intermediate magnetic layer formed of a perpendicular magnetization film formed in contact with the non-magnetic layer, and A second intermediate magnetic layer formed in contact with the first intermediate magnetic layer and changing from an in-plane magnetized film to a perpendicular magnetized film at a predetermined temperature or higher; and a recording layer formed in contact with the second intermediate magnetic layer. A reproducing device for reproducing a magneto-optical recording medium including
The peak magnetic field in the direction of the initializing magnetization of the intermediate magnetic layer is larger than the peak magnetic field in the direction opposite to the direction of the initializing magnetization and is larger than the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer. A reproducing apparatus for a magneto-optical recording medium, which includes a magnetic head for applying an alternating magnetic field having the above to the magneto-optical recording medium, and an optical head for irradiating the magneto-optical recording medium with laser light. In the reproducing apparatus for a magneto-optical recording medium according to claim 2, when an alternating magnetic field is applied to the magneto-optical recording medium from a magnetic head and the magneto-optical recording medium is irradiated with laser light from the optical head, a second intermediate magnetic field is generated. A region of the layer above a predetermined temperature is changed from an in-plane magnetization film to a perpendicular magnetization film and exchange-coupled with a magnetic domain of the recording layer, and a region below a predetermined temperature retains in-plane magnetization and exchange-coupling with the magnetic domain of the recording layer. do not do. Then, in a region of the first intermediate magnetic layer having a predetermined temperature or higher, a region weaker than the peak magnetic field of the alternating magnetic field to which the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer is applied, All regions have the same magnetization as the direction of the alternating magnetic field and the magnetization is inverted by the alternating magnetic field in a region stronger than the peak magnetic field of the alternating magnetic field to which the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer is applied. Instead, it is transferred to the reproducing layer by magnetostatic coupling through the non-magnetic layer. And
The magnetic domain transferred to the reproducing layer is detected by the laser beam as the magnetic domain is expanded by the applied alternating magnetic field. In this case, since the peak magnetic field in the direction of the initialization magnetization of the first intermediate magnetic layer is larger than the peak magnetic field in the direction opposite to the direction of the initialization magnetization, the magnetic domain of the recording layer having the magnetization in the direction opposite to the initialization magnetization is After being transferred to the reproducing layer, the magnetic domain is expanded, and the magnetization in a region weaker than the peak magnetic field of the alternating magnetic field to which the exchange coupling force between the first intermediate magnetic layer and the second intermediate magnetic layer is applied is changed by the alternating magnetic field. However, since it is not a change in the magnetization that reflects the magnetization of the recording layer, it does not affect the detection of the magnetic domain expanded in the reproducing layer. Therefore, according to the first aspect of the present invention, the low temperature region and the high temperature region within the spot diameter of the laser beam applied to the magneto-optical recording medium are masked to make the magnetic domain of the recording layer a high density reproducing layer. The transferred magnetic domain can be detected by expanding it with an alternating magnetic field.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. With reference to FIG. 1, a cross-sectional structure of a magneto-optical recording medium which is a target of a reproducing apparatus for a magneto-optical recording medium according to the present invention will be described. The magneto-optical recording medium 10 includes a translucent substrate 1, an underlayer 2, a reproducing layer 3, a nonmagnetic layer 4, a first intermediate magnetic layer 5, a second intermediate magnetic layer 6, and a recording layer. 7
And a protective film 8. The transparent substrate 1 is made of glass, polycarbonate, etc., the underlayer 2 is made of SiN, the reproducing layer 3 is made of transition metal-rich GdFeCo, the nonmagnetic layer 4 is made of SiN, and the first intermediate layer is formed. The magnetic layer 5 is made of transition metal-rich GdFeCo, the second intermediate magnetic layer 6 is made of rare earth metal-rich GdFeCo, the recording layer 7 is made of TbFeCo, and the protective film 8 is used.
Is made of SiN. SiN forming the underlayer 2, transition metal-rich GdFeCo forming the reproducing layer 3, SiN forming the nonmagnetic layer 4, transition-metal-rich GdFeCo forming the first intermediate magnetic layer 5, second intermediate magnetism The rare earth metal-rich GdFeCo forming the layer 6, the TbFeCo forming the recording layer 7, and the Si forming the protective film 8.
N is formed by the RF magnetron sputtering method. The underlayer 2 has a film thickness of 400 to 800Å, the reproducing layer 3 has a film thickness of 150 to 500Å, and the nonmagnetic layer 4 has a film thickness of 50 to 300Å. The layer 5 has a film thickness of 400 to 1500Å, the second intermediate magnetic layer 6 has a film thickness of 400 to 1500Å, the recording layer 7 has a film thickness of 300 to 2000Å, and the protective film 8 has a film thickness. Is 400 to 800Å. The reproducing layer 3, the non-magnetic layer 4, the first intermediate magnetic layer 5, the second intermediate magnetic layer 6, and the recording layer 7 will be described with reference to FIG. The reproduction layer 3 is
It is a perpendicular magnetization film and is initialized in advance so as to have a certain direction of magnetization by an external magnetic field when a signal is reproduced from the magneto-optical recording medium 10. However, this initialization only needs to be performed once, and when repeated reproduction is performed, it is not necessary to perform initialization for each reproduction. The first intermediate magnetic layer 5 is a magnetic layer that is a perpendicular magnetization film. Then, the first intermediate magnetic layer 5 is initialized at the same time when the reproducing layer 3 is initialized and has magnetization in a fixed direction. In addition, the second intermediate magnetic layer 6
Is an in-plane magnetized film at room temperature and a magnetic layer that becomes a perpendicular magnetized film at a predetermined temperature or higher. The recording layer 7 is a perpendicular magnetization film magnetized in different directions based on the recording signal. Therefore, the magneto-optical recording medium 10 is
As shown in FIG. 2, each layer has magnetization. The mechanism by which each magnetic domain of the recording layer 7 is transferred to the reproducing layer 3 with high resolution will be described in detail with reference to FIG. When the laser beam LB is irradiated to the magneto-optical recording medium 10 rotating at a predetermined rotation speed, the temperature of the magneto-optical recording medium 10 reaches the maximum at a position L1 behind the optical axis LB0 of the laser beam LB, and the position The temperature distribution of the magneto-optical recording medium 10 is steeper on the traveling direction 9 side of the laser beam LB than L1, and the temperature distribution of the magneto-optical recording medium is broader on the side opposite to the traveling direction 9 of the laser beam LB from the position L1. Under such temperature distribution, the second intermediate magnetic layer 6
Changes from the in-plane magnetized film to the perpendicular magnetized film at temperature T1.
Therefore, in the temperature region higher than the temperature T1 of the second intermediate magnetic layer 6, there are magnetic domains 60 and 62 having perpendicular magnetization exchange-coupled with the magnetic domains 70 and 72 of the recording layer 7, and the temperature T1
In the lower temperature region, there are magnetic domains 63 having in-plane magnetization. Further, in the temperature region of the first intermediate magnetic layer 5 higher than the temperature T2, the first intermediate magnetic layer 5 is higher than the region in the temperature range of T1 to T2.
Since the exchange coupling force between the intermediate magnetic layer 5 and the second intermediate magnetic layer 6 is weak, the magnetic field in the same direction as the initializing magnetization in the alternating magnetic field Hex is entirely directed to the initializing magnetization. as a result,
In the temperature region higher than the temperature T2 of the first intermediate magnetic layer 5, the magnetic domain 52 having the magnetization in the same direction as the initialization magnetization exists, and the region in the temperature range of T1 to T2 is exchanged with the second intermediate magnetic layer 6. Since the coupling force is stronger than the alternating magnetic field Hex, the magnetic domain 50 having the magnetization 51 in the same direction as the magnetization 61 of the magnetic domain 60 exists.
In the temperature region lower than the temperature T2, the initialized perpendicular magnetization is maintained. Then, the magnetic domain 72 existing in the temperature region higher than the temperature T2 in the recording layer 7 is transferred to the second intermediate magnetic layer 6 as the magnetic domain 62, but the first intermediate magnetic layer 5 is formed.
Transfer to the reproducing layer 3 is blocked by the magnetic domains 52 of the. Further, the magnetic domain 73 existing in the temperature region lower than the temperature T1 in the recording layer 7 is prevented from being transferred to the reproducing layer 3 by the magnetic domain 63 having the in-plane magnetization of the second intermediate magnetic layer 6. Therefore, in the recording layer 7, the magnetic domain 70 having the magnetization 71 in the temperature range from T1 to T2 becomes the perpendicular magnetization film at the temperature T1 or higher because the second intermediate magnetic layer 6 becomes the perpendicular magnetization film, so that the second intermediate magnetic layer is formed by exchange coupling. Transferred to the magnetic layer 6 as the magnetic domain 60 having the magnetization 61 in the same direction as the magnetization 71. In the first intermediate magnetic layer 5, the region in the temperature range of T1 to T2 is the exchange coupling force with the second intermediate magnetic layer 6. Is stronger than the alternating magnetic field Hex, the magnetic domain 60 of the second intermediate magnetic layer 6 is transferred to the first intermediate magnetic layer 5 as a magnetic domain 50 having a magnetization 51 in the same direction as the magnetization 61 by exchange coupling. Then, the magnetic domain 50 of the first intermediate magnetic layer 5 is transferred as the magnetic domain 30 to the reproducing layer 3 via the nonmagnetic layer 4 by the leakage magnetic field. In the present invention, the second
The temperature T1 at which the intermediate magnetic layer 6 changes from the in-plane magnetized film to the perpendicular magnetized film is set in the range of 100 to 150 ° C. The temperature difference between the temperature T1 and the temperature T2 is preferably in the range of 20 to 40 ° C. By setting T2 to T1 in the range of 20 to 40 ° C., each magnetic domain of the recording layer 7 is independently reproduced. Can be transferred to. Laser beam LB intensity, magneto-optical recording medium 10
In the magneto-optical recording medium 10, since the region where the temperature changes from T1 to T2 can be reduced to the shortest domain length by controlling the rotation speed of the recording layer 7,
Each magnetic domain can be independently transferred to the reproducing layer 3. As a result, high resolution signal reproduction is possible. Referring to FIG. 4, a process of magnetic domain expansion reproduction in the magneto-optical recording medium 10 will be described. Before the magneto-optical recording medium 10 is irradiated with the laser beam LB, the reproducing layer 3 and the first intermediate magnetic layer 5 are initialized by an external magnetic field (see (a) of FIG. 4). When the magneto-optical recording medium 10 is irradiated with laser light, the magnetic domain 70 in the recording layer 7 having a temperature in the range of T1 to T2 is transferred to the reproducing layer 3 as the magnetic domain 30 as described in FIG. (See FIG. 4B). The magnetic domains 30 transferred to the reproducing layer 3 are
Of the alternating magnetic field Hex, the magnetic domain 30 is expanded to the magnetic domain 300 at the timing when a magnetic field in the same direction as the magnetization of the magnetic domain 30 is applied. Then, the enlarged magnetic domain 300 and the laser beam L
The reflected light of the laser beam LB has its polarization plane rotated by the magneto-optical action with B, and the magnetic domain 300 is detected by detecting the reflected light with the polarized plane rotated (see FIG. 4C). In this case, the magnetic domain 50 in the first intermediate magnetic layer 5
The magnetic domain 52 existing in a higher temperature region than the region of
Although the magnetization directions change following ex, they all have the same magnetization directions and do not reflect the magnetization directions of the magnetic domains 72 of the recording layer 7, which adversely affects the expansion and detection of the magnetic domains 30. There is no such thing. After the magnetic domain 300 is detected, the laser beam LB moves, and when the temperature of the regions of the magnetic domains 70, 60, 50, 300 drops, the state returns to the initial state (see (a) of FIG. 4). Through the steps (a) to (c) of FIG. 4 described above, each magnetic domain of the recording layer 7 is independently transferred to the reproducing layer 3 and is detected in the reproducing layer 3 by being expanded by the alternating magnetic field Hex. In the above description, the reproducing layer 3 of the magneto-optical recording medium 10 has been described as a perpendicular magnetization film, but the present invention is not limited to this, and it is an in-plane magnetization film at room temperature and a perpendicular magnetization film at a predetermined temperature or higher. It may be a magnetic layer that changes to. A reproducing apparatus for a magneto-optical recording medium according to the present invention will be described with reference to FIG. A reproducing apparatus 100 for a magneto-optical recording medium includes an optical head 11, a reproduction signal amplifier circuit 12, a servo circuit 13, a servo mechanism 14, a spindle motor 15, and
A difference unit 16, a decoder 18, a control circuit 19, a magnetic head drive circuit 20, a laser drive circuit 21, and a magnetic head 22 are provided. The optical head 11 is the magneto-optical recording medium 1
0 is irradiated with laser light and the reflected light is detected. The reproduction signal amplifier circuit 12 inputs the focus error signal, the tracking error signal, and the magneto-optical signal detected by the optical head 11 and amplifies them to a predetermined value, and then extracts the focus error signal, the tracking error signal, and the magneto-optical signal. The generated synchronization signal is output to the servo circuit 13, and the magneto-optical signal is output to the differentiator 16. The servo circuit 13 controls the servo mechanism 14 based on the input focus error signal and tracking error signal, and the servo mechanism 14 controls the focus of an objective lens (not shown) in the optical head 11 based on the control of the servo circuit 13. Perform servo and tracking servo. Further, the servo circuit 13 rotates the spindle motor 15 at a predetermined rotation speed in synchronization with the input synchronization signal. The spindle motor 15 rotates the magneto-optical recording medium 10 at a predetermined rotation speed. The differentiator 16 cuts the noise of the magneto-optical signal input from the reproduction signal amplifier circuit 12, and then outputs it as a reproduction signal to the decoder 18.
The decoder 18 demodulates the reproduction signal from the differentiator 16 and outputs it as reproduction data. The control circuit 19 outputs a signal (b) (or (b2)) to the magnetic head drive circuit 20,
The signal (a) is output to the laser drive circuit 21. The magnetic head drive circuit 20 drives the magnetic head 22 based on the signal (b) (or (b2)). Laser drive circuit 21
Drives a semiconductor laser (not shown) in the optical head 11 based on the signal (a). The magnetic head 22 applies a predetermined magnetic field to the magneto-optical recording medium 10. Signals output by the control circuit 19 will be described with reference to FIG. When performing signal reproduction from the magneto-optical recording medium 10 by expanding magnetic domains, continuous laser light is emitted. Therefore, the signal output from the control circuit 19 to the laser drive circuit 21 is a signal (a) having a constant value so that the intensity of the laser light emitted from the optical head 11 is constant. In the present application, the control circuit 19 outputs the signal (a) such that the intensity of the laser beam applied to the magneto-optical recording medium 10 becomes 2.0 mW.
Output to the laser drive circuit 21. On the other hand, the control circuit 19
The signal output to the magnetic head drive circuit 20 is the signal (b)
Is. Again referring to FIG. 4, in the present invention,
The magnetic domain 70 of the recording layer 7 of the magneto-optical recording medium 10 is transferred to the second intermediate magnetic layer 6 and the first intermediate magnetic layer 5 by exchange coupling, and the magnetic domain 50 of the first intermediate magnetic layer 5 is magnetostatically coupled. When transferred to the reproducing layer 3, the magnetization of the magnetic domain 52 existing in a region higher in temperature than the region of the magnetic domain 50 in the first intermediate magnetic layer 5 is directed in the opposite direction to the magnetization 51 of the transferred magnetic domain 50. Need to be. It is the magnetic domain 5 of the first magnetic layer 5.
This is because when the magnetization direction of No. 2 is opposite to the magnetization direction 51 of the magnetic domain 50, the seed magnetic domain necessary for transfer is not generated in the reproducing layer 3 due to the influence of the magnetic domain 52. However, this is only the case where the magnetic domain having the magnetization in the opposite direction to the initializing magnetization of the reproducing layer 3 is transferred to the reproducing layer 3, and the magnetic domain having the same magnetization as the initializing magnetization of the reproducing layer 3 is reproduced. When transferring to No. 3, it is not necessary. Therefore, the alternating magnetic field applied to the magneto-optical recording medium 10 is the magnetization 51 of the magnetic domain 50.
The time for applying a magnetic field in the opposite direction to
The signal (b) shown in FIG. 6 is output from the control circuit 19 to the magnetic head drive circuit 20 because it needs to be set longer than the time for applying the magnetic field in the same direction as 1. In the present invention, the duty (t2 / t1 + t2) of the signal (b)
Is set in the range of 15 to 50%. As a result, the alternating magnetic field shown in (c) is applied to the magneto-optical recording medium 10 from the magnetic head 22. The peak magnetic field of the alternating magnetic field is +3
00Oe and -300Oe, frequency is 25MHz
Is. In general, the peak magnetic field of the alternating magnetic field may be a value that is stronger than the exchange coupling force between the first intermediate magnetic layer 5 and the second intermediate magnetic layer 6 in the region of temperature T2 or higher. Magnetic field H1
Is applied to the magnetic domain 50 of the first intermediate magnetic layer 5.
Is transferred to the reproducing layer 3, and the magnetic domain 30 transferred to the reproducing layer 3 is enlarged while the magnetic field H2 is applied. Then, after that, the magnetic domain 300 expanded in the state where the magnetic field H3 is applied disappears. The signal output from the control circuit 19 to the magnetic head drive circuit 20 is not limited to the signal (b), but may be the signal (b2) shown in FIG. Signal (b
2) is a signal for generating an alternating magnetic field (b2) from the magnetic head 22 in which the negative peak magnetic field is larger than the positive peak magnetic field. The reason why the peak magnetic field on the negative side of the alternating magnetic field applied to the magneto-optical recording medium 10 is made stronger than the peak magnetic field on the positive side is to eliminate the influence of the magnetic domain 52 of the first intermediate magnetic layer 50 and Magnetic domain 50
This is because a seed magnetic domain for transfer is surely generated in the reproducing layer 3 when the magnetic field is transferred to the reproducing layer 3. Alternating magnetic field (c
In 2), since the peak magnetic field on the negative side is stronger than the peak magnetic field on the positive side, the time period during which the magnetic field on the negative side is applied to the magneto-optical recording medium 10 can be lengthened. Here, the minus means the direction of the initialization magnetization of the first intermediate magnetic layer 5, and the plus means the first intermediate magnetic layer 5.
The direction opposite to the initialization magnetization of. In the alternating magnetic field (c2), the peak magnetic field on the positive side is +300 Oe,
The negative peak magnetic field is -500 Oe and the frequency is 25 MHz. Therefore, even when the alternating magnetic field (c2) is applied from the magnetic head 22 to the magneto-optical recording medium 10, the magnetic domain 50 of the first intermediate magnetic layer 5 is transferred to the reproducing layer 3 while the magnetic field H1 is applied. , The magnetic domain 30 transferred to the reproducing layer 3 is expanded while the magnetic field H2 is applied. Then, after that, the magnetic domain 300 expanded in the state where the magnetic field H3 is applied disappears. Figure 5 again
Signal reproduction from the magneto-optical recording medium 10 by expanding magnetic domains will be described with reference to FIG. When the magneto-optical recording medium 10 is rotated at a predetermined rotation speed by the spindle motor 15, the control circuit 19 outputs a signal (a) to the laser drive circuit 21,
The laser drive circuit 21 drives a semiconductor laser (not shown) in the optical head 11 based on the signal (a). The optical head 11 emits a laser beam having a predetermined intensity to the magneto-optical recording medium 1.
Irradiate to 0. After that, the optical head 11 detects the focus error signal and the tracking error signal, and as described above, the focus servo and the tracking servo of the objective lens (not shown) in the optical head 11 are performed. Then, after the focus servo and tracking servo of the objective lens, the control circuit 19 outputs a signal (b) (or signal (b2)) to the magnetic head drive circuit 20, and the magnetic head drive circuit 20 outputs the signal (b) (or The magnetic head 22 is driven based on the signal (b2), and the magnetic head 22 applies the alternating magnetic field (c) (or (c2)) to the magneto-optical recording medium 10. The optical head 11 is irradiated with a constant intensity laser beam and is applied with the alternating magnetic field (c) (or (c2)), and the alternating magnetic field (c) (or (c
2)) to detect a magneto-optical signal whose amplitude changes,
Output to the reproduction signal amplifier circuit 12. After that, it is output as reproduction data through the process described above. As a result, each magnetic domain of the recording layer 7 of the magneto-optical recording medium 10 is independently transferred to the reproducing layer 3 by the reproducing device 100, enlarged, and detected.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a magneto-optical recording medium targeted by the present invention.

FIG. 2 is a diagram for explaining the magnetization distribution of each layer of the magneto-optical recording medium shown in FIG.

FIG. 3 is a diagram for explaining the transfer of magnetic domains from the recording layer to the reproducing layer of the magneto-optical recording medium shown in FIG.

FIG. 4 is a diagram illustrating a process of magnetic domain expansion reproduction of the magneto-optical recording medium shown in FIG.

FIG. 5 is a block diagram of a reproducing apparatus for a magneto-optical recording medium according to the present invention.

FIG. 6 is a signal output by the control circuit shown in FIG.

7 is another signal output from the control circuit shown in FIG. 5 to the magnetic head drive circuit shown in FIG.

FIG. 8 is a cross-sectional structure of a conventional magneto-optical recording medium.

FIG. 9 is a diagram illustrating a problem of a conventional magneto-optical recording medium.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Underlayer 3 ... Reproducing layer 4 ... Nonmagnetic layer 5 ... First intermediate magnetic layer 6 ... Second intermediate magnetic layer 7 ... Recording layer 8 ... Protective layer 10, 200 ... Magneto-optical recording medium 30, 50, 52, 53, 60, 62, 63, 70, 7
2, 73, 300 ... Magnetic domains 51, 61, 71, ... Magnetization 100 ... Playback device 11 ... Optical head 12 ... Playback signal amplification circuit 13 ... Servo circuit 14 ... Servo Mechanism 15 ... Spindle motor 16 ... Difference device 18 ... Decoder 19 ... Control circuit 20 ... Magnetic head drive circuit 21 ... Laser drive circuit 22 ... Magnetic head

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 11/10-11/105

Claims (2)

(57) [Claims] 1. A reproducing layer, a nonmagnetic layer formed in contact with the reproducing layer, a first intermediate magnetic layer formed of a perpendicular magnetization film formed in contact with the nonmagnetic layer, and the first magnetic layer. A second intermediate magnetic layer formed in contact with the intermediate magnetic layer and changing from an in-plane magnetized film to a perpendicular magnetized film at a predetermined temperature or higher; and a recording layer formed in contact with the second intermediate magnetic layer In a reproducing device for reproducing a magneto-optical recording medium, an application time in a direction of initialization magnetization of the first intermediate magnetic layer is longer than an application time in a direction opposite to the initialization magnetization, and the first intermediate magnetic layer and the Magneto-optical including a magnetic head for applying an alternating magnetic field having a peak magnetic field larger than the exchange coupling force with the second intermediate magnetic layer to the magneto-optical recording medium, and an optical head for irradiating the magneto-optical recording medium with laser light. Recording medium reproducing device. 2. A reproducing layer, a non-magnetic layer formed in contact with the reproducing layer, a first intermediate magnetic layer formed of a perpendicular magnetization film formed in contact with the non-magnetic layer, and the first magnetic layer. A second intermediate magnetic layer formed in contact with the intermediate magnetic layer and changing from an in-plane magnetized film to a perpendicular magnetized film at a predetermined temperature or higher; and a recording layer formed in contact with the second intermediate magnetic layer In a reproducing device for reproducing a magneto-optical recording medium, the first intermediate magnetic layer has a peak magnetic field in a direction of initialization magnetization larger than a peak magnetic field in a direction opposite to the direction of initialization magnetization. And a magnetic head for applying an alternating magnetic field having a peak magnetic field larger than the exchange coupling force between the magneto-optical recording medium and the second intermediate magnetic layer, and an optical head for irradiating the magneto-optical recording medium with laser light. Reproducing device for magneto-optical recording medium.