JPH06162593A - Initializing method for magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve the reliability of a magneto-optical recording medium by initializing the initializing layer of the recording medium and preventing the operational defect of overwrite caused by the destruction of the initializing layer. CONSTITUTION:When data are '1', the write operation is same as writing by a normal method, and the data are magnetized in the same direction as a bias magnetic field. When data are '0', on the other hand, a magneto-optical disk is irradiated with stronger laser light than that at the time when the data are written as '0'. Thus, the temperature of the laser light-irradiated part is increased almost to the Curie temperature of a magnetic layer 13 and when the temperature is lowered after a magnetic layer 15 is disappeared, the magnetic layer 13 is magnetized in the same direction as a magnetic layer 14. Therefore, magnetic layers 14-16 can be overwritten many times in the same direction. When an error rate is smaller than a prescribed reference value after the write is completed, it is verified that the initializing layer 16 is normally initialized and normally overwritten. On the other hand, when the error rate is larger than a prescribed reference value, the destruction of the layer 16 is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium initialization method, and more particularly to a magneto-optical recording medium initialization method having an initialization layer.

In a magneto-optical recording medium, particularly a rewritable magneto-optical disk, a submicron-order recording mark is recorded on the medium by using a laser beam, and by reproducing this, a floppy disk which has been a conventional recording medium is recorded. Since the recording capacity can be remarkably increased as compared with a disk or a hard disk, in recent years, it has been highlighted as a large-capacity external recording medium for a computer.

For example, a magneto-optical disk has a diameter of 3.5 inches and has a storage capacity of about 128 MB per side. On the other hand, a 3.5 inch diameter floppy disk has a storage capacity of about 1 MB per side, so one magneto-optical disk can have a storage capacity of 128 floppy disks. As described above, the magneto-optical disk is an exchangeable recording medium having a very high recording density.

However, the magneto-optical disk is more advantageous than the hard disk in terms of storage capacity and exchangeability, but regarding the data transfer rate, for example, the rotation speed is 36.
The rotation speed is 2400-3000 rpm for magneto-optical disks, while it is about 3 MB / s for 00 rpm hard disks.
It is about 640 KB / s. In the case of a magneto-optical disk, this is done by not overwriting such that new recording information is directly overwritten on the recording track that is being performed on the hard disk at the time of recording. This is because it is necessary to record at least one rotation for erasing, one rotation for recording, and one rotation for verifying, and the transfer speed becomes slower by the amount of erasing.

Therefore, in recent years, a recording method for overwriting a magneto-optical disk has been actively developed. A magneto-optical recording medium having an initialization layer is known as a magneto-optical recording medium capable of performing such overwrite (Lecture No. 23a of the 13th Academic Meeting of the Applied Magnetics Society of Japan).
C-4). This magneto-optical recording medium needs to be able to overwrite again even if the initialization layer is destroyed.

[0006]

2. Description of the Related Art Conventional recording methods for overwriting are roughly classified into a magnetic field modulation method and an optical modulation method. The magnetic field modulation method is a recording method in which a magneto-optical disk with a single-layer film is overwritten by using a magnetic head. The polarity of the magnetic field applied to the magnetic disk is reversed. Therefore, in this magnetic field modulation method, the overwrite speed is determined by the magnetic field reversal time of the magnetic head.

On the other hand, the optical modulation method overwrites the magneto-optical disk having a multilayer film by changing the intensity of laser light. Therefore, in this light modulation method, the overwrite speed is determined by the intensity change time of the laser light, and generally has an advantage that high-speed recording is possible as compared with the magnetic field modulation method.

In this optical modulation method, for example, a magneto-optical recording medium having a sectional structure as shown in FIG. 7 can be used. This recording medium has a two-layer structure in which a protective film 2, a first magnetic layer 3, a second magnetic layer 4 and a protective layer 5 are sequentially laminated on a disk-shaped transparent substrate 1 (the protective layers 2 and 5 are (Not counting). The protective layers 2 and 5 are each made of Tb-SiO ₂ . The first magnetic layer 3 is TbFe
It is made of Co and is used as a memory layer. The second magnetic layer 4 is made of TbDyFeCo and is used as a recording layer.

The first magnetic layer 3 of this magneto-optical recording medium is set to have a lower Curie temperature and a higher coercive force than the second magnetic layer 4. Since the magnetic field of the initializing magnet is smaller than the coercive force of the first magnetic layer 3 and larger than the coercive force of the second magnetic layer 4, only the second magnetic layer 4 moves in the same direction as the initializing magnetic field by the initializing magnet. Is magnetized.

The first magnetic layer 3 is formed into the second magnetic layer 3 by the exchange coupling force.
The magnetization directions are aligned in the same direction as the magnetization of the magnetic layer 4 of FIG. 2, but when the laser light intensity is high, the two magnetic layers 3 and 4 are heated to the Curie temperature or higher. The bias magnetic field magnetizes the second magnetic layer 4, and the first magnetic layer 3 is also magnetized in the same direction as the second magnetic layer 4 (Japanese Patent Laid-Open No. 62-175948).

Overwriting can be performed using the above-mentioned magneto-optical recording medium having a two-layer structure, but the initialization magnetic field requires a strength considerably larger than the bias magnetic field, and the initialization magnet becomes large. Therefore, as a magnetic recording medium having a four-layer structure as shown in FIG.

In the figure, first to fourth magnetic layers 13 to 16 are sequentially laminated on a disk-shaped transparent substrate 11 via a protective layer 12, and a protective film 17 is further formed on the fourth magnetic layer 16. It is covered. The first magnetic layer 13 is made of TbFeCo,
Information is recorded and retained. The second magnetic layer 14 is TbDyF
It is made of eCo and determines the direction of magnetization of the first magnetic layer 13. The third magnetic layer 15 is made of TbFe and has a Curie temperature set lower than those of the other magnetic layers 13, 14, 16. Further, the fourth magnetic layer 16 is made of TbCo and is a layer for initializing the second magnetic layer 14, and is set to have the highest Curie temperature and functions as the initializing magnet.

When overwriting is performed on the four-layered magneto-optical recording medium by an optical modulation method, a low-power laser beam is irradiated from the substrate 11 side so that the first magnetic layer 13 is formed into a second layer. The second magnetic layer 14 is once magnetized in the direction of the bias magnetic field by recording "0" by magnetizing in the same direction as the magnetic direction of the magnetic layer 14 of FIG. Then by exchange coupling force first
Magnetizing the magnetic layer 13 in the same direction as the second magnetic layer 14,
Record “1”.

The fourth magnetic layer 16, which is the initialization layer, is magnetized together with the third magnetic layer 15 in the direction opposite to the bias magnetic field in advance, and at the end of recording, regardless of the recorded information, the fourth magnetic layer 16 and the second magnetic layer 14 are formed. The third magnetic layer 15 is magnetized in the same direction as the magnetization of the initialization layer (fourth magnetic layer 16).

[0015]

Therefore, in the four-layered magneto-optical recording medium shown in FIG. 8 described above, the fourth magnetic layer 16 as the initialization layer must always be magnetized in the initialization direction. There is. However, the fourth magnetic layer 16 is only magnetized in a predetermined direction in a strong magnetic field after the magneto-optical recording medium is manufactured, and has a coercive force larger than an external magnetic field so as not to cause magnetization reversal during recording. However, the fourth magnetic layer 16 may be destroyed for some reason.
However, conventionally, there is no means for determining whether or not the initialization layer (fourth magnetic layer 16) has been destroyed. Therefore, when the initialization layer is destroyed, the overwriting is performed in the same manner as when other causes of defects are generated. could not.

The present invention has been made in view of the above points,
An object of the present invention is to provide a method for initializing a magneto-optical recording medium which solves the above problems by performing initialization when the initialization layer is destroyed.

[0017]

FIG. 1 is a flow chart for explaining the principle of the method of the present invention.
And the second step 102 are sequentially executed. Here, the first step 101 uses a memory layer used for recording and reproducing information, an initialization layer that is always magnetized in one direction, and an exchange coupling force formed between the memory layer and the initialization layer. Verification is performed on a magneto-optical recording medium having a plurality of layers formed on at least a substrate, and when the error rate is equal to or higher than a first reference value, known data is written after erasing.

In a second step 102, verification is performed on the magneto-optical recording medium that has undergone the first step 101, and when the error rate is less than a second reference value, the initialization layer is initialized. Write.

[0019]

When the cause of failure in recording on the magneto-optical recording medium is destruction of the initializing layer, the error rate is small and the degree of defects is small compared to other causes of defects. When it is determined in step 102 that the error rate after verification is less than the second reference value, it can be determined that the cause of the failure is the destruction of the initialization layer. Therefore, at this time, writing is performed in the second step 102 so that the magnetization direction of the initialization layer is the original direction. Thereby, the initialization layer of the magneto-optical recording medium can be initialized.

[0020]

2 is a block diagram showing an example of a magneto-optical disk device used in the method of the present invention. In the figure, a magneto-optical disk device 20 records information on the magneto-optical disk 10 by an optical head 21, and also reproduces, erases, and verifies already recorded information. The magneto-optical disk 10 is a magneto-optical recording medium using the conventional rare earth-transition metal amorphous ferrimagnetic alloy having a four-layer structure shown in FIG. 8, and includes a first magnetic layer 13 used for recording and reproducing information. , A second magnetic layer 14 that assists writing and erasing to the first magnetic layer 13, a fourth magnetic layer 16 that is always magnetized in one direction, that is, an initialization layer, and a fourth magnetic layer. At least on the substrate 11, there is a third magnetic layer 15 that transmits the magnetization of 16 to the second magnetic layer 14 by a magnetic interaction (exchange coupling force) below the Curie temperature of the layer.

The magneto-optical disk 10 is rotated in a predetermined direction by the spindle motor 22 shown in FIG. A laser beam 23 is irradiated from the optical head 21 to the substrate 11 side of the magneto-optical disk 10, and a bias magnetic field Hb is applied from the direction of the protective film 17 by a bias magnet 24 near the irradiation position. The magneto-optical disk 10 does not require an initialization magnet because the fourth magnetic layer 16 which is an initialization layer has a role of an initialization magnet.

The drive controller 25 is a control device for controlling the operation of the entire magneto-optical disk device 20, and is connected to a host device (usually a computer) via a predetermined external interface (eg SCSI interface). The signal processing circuit 26 generates data modulated by a predetermined modulation method during recording and demodulates a reproduction pulse during reproduction. The optical head control circuit 27 converts the recording data into recording pulses during recording, and performs AGC (automatic gain control) or waveform equalization on the reproduction signal from the optical head 21 during reproduction, and converts it into pulses.

The optical head 21 generates a laser beam 23 whose light intensity is modulated by a recording pulse from the optical head control circuit 27 and irradiates the magneto-optical disk 10 with the laser beam 23. At the time of reproduction, the laser power of the laser beam 23 is used. The magneto-optical disk 10 is irradiated with a controlled constant value, and the reflected light from the magneto-optical disk 10 is received through an optical system to detect a change in the quantity of the reflected light or a rotation of the reflective polarization plane to reproduce a reproduction signal or the like. To get

The bias magnet control circuit 28 also supplies a drive current to the bias magnet 24 to generate a bias magnetic field, and the direction of the bias magnetic field also depends on a control signal input from the drive controller 25 via the bus 30. Control. The error rate determination circuit 29 determines the error rate based on the reproduction pulse input from the signal processing circuit 26 via the bus 30, and notifies the drive controller 25 of the determination result via the bus 30.

Although most of the configuration shown in FIG. 2 is known, this embodiment is characterized in that the drive controller 25 executes the post-processing routine shown in FIG. 3 after writing by overwriting. Have. That is,
As shown in FIG. 3, a verify operation is performed to confirm whether or not the writing by the overwrite performed immediately before is normal (step 41), and the error rate determination circuit 2 is executed.
According to 9, it is determined whether or not the error rate at that time is smaller than the first reference value (step 42).

When the error rate is less than the first reference value, it is determined that the overwrite writing is normally performed, and this routine is ended. On the other hand, when the error rate is equal to or higher than the first reference value, there are many data errors, so erasing and writing are sequentially performed by the normal method (step 4).
4). This is an operation for discriminating whether the cause of non-recording is due to malfunction of overwriting (breakage of the initialization layer) or other cause (dirt of the magneto-optical disk 10 or the like).

Here, the erase and write operations in the above-mentioned normal method will be described in more detail. In the erasing by the normal method, as shown in FIG. 4A, the direction of the bias magnetic field by the bias magnet 24 with respect to the magneto-optical disk 10 is set by the bias magnet control circuit 28 on the side opposite to that at the time of writing (FIG.
(A) (upward) and the light intensity of the laser light 23 from the optical head 21 is set to a large value (high power) so that the temperature of the second magnetic layer 14 rises to near the Curie temperature. .

As a result, the magnetization direction of the second magnetic layer 14 is magnetized in the direction of the bias magnetic field, as schematically shown in FIG. 4 (B). At this time, the first and third magnetic layers 13
Since Nos. 15 and 15 are above the Curie temperature, the magnetization disappears. At this time, the direction of the magnetization of the fourth magnetic layer (hereinafter referred to as the initialization layer) 16 is unknown, so that it is shown by a broken line in FIG.

Here, the Curie temperature of each magnetic layer is highest in the initialization layer 16 and is set to be smaller in the order of the second magnetic layer 14, the first magnetic layer 13 and the third magnetic layer 15 in the following order. There is.
Therefore, as the laser light irradiation portion magnetized as shown in FIG. 4B moves away from the position where the laser light is irradiated, the temperature of the portion is cooled by the Curie temperature of the first magnetic layer 13, The Curie temperature of the magnetic layer 15 of No. 3 gradually decreases. When the temperature is lower than the Curie temperature of the first magnetic layer 13, the first magnetic layer 13 is magnetized in the same direction as the second magnetic layer 14 by the exchange coupling force as schematically shown in FIG.

When the temperature further decreases and becomes equal to or lower than the Curie temperature of the third magnetic layer 15, the magnetization of the third magnetic layer 15 is generated, and the initialization layer 16 is formed as schematically shown in FIG. The second magnetic layer 14 is magnetized in the same direction as the magnetization direction of the initialization layer 16 via the third magnetic layer 15 by the exchange coupling force.

Then, normal writing is performed on this erased portion. In this case, as schematically shown in FIG. 5A, the direction of the bias magnetic field by the bias magnet 24 is set to the direction opposite to that at the time of erasing by the bias magnet control circuit 28, and the laser light from the optical head 21 is emitted. The light intensity is set to a value (the high power) such that the temperature of the second magnetic layer 14 rises to near the Curie temperature. As a result, as schematically shown in FIG. 5B, the second magnetic layer 1
4 is magnetized in the direction of the bias magnetic field, and the magnetizations of the first and third magnetic layers 13 and 15 having a Curie temperature or higher disappear.

As the laser light irradiation portion magnetized in this way moves away from the laser light irradiation position, the temperature decreases, and the first
5 is lower than the Curie temperature of the magnetic layer 13 of FIG.
As schematically shown in (C), the exchange coupling force of the second magnetic layer 14 magnetizes the first magnetic layer 13 in the same direction as the second magnetic layer 14.

When the temperature further decreases and becomes equal to or lower than the Curie temperature of the third magnetic layer 15, the magnetization of the initialization layer 16 is changed by the exchange coupling force as shown schematically in FIG. 5D. To magnetize the second magnetic layer 14. At this time, the first magnetic layer 13 is not magnetized. This is because the coercive force of the first magnetic layer 13 and the like are set as such.

In this way, the known data “1” is written in the first magnetic layer 13. Further, the known data “0” is set in the first magnetic layer 13 with the magnetization state at the time of erasing shown in FIG.

Referring back to FIG. 3 again, after the erase and write operations by the above-mentioned normal method are completed, verification is performed (step 45), and the error rate at that time is the second.
Reference value (this may be the same as the first reference value,
The error rate judging circuit 29 judges whether the difference is smaller than the different value (step 46).

When the error rate is smaller than the second reference value and the writing is performed normally, the cause of the writing failure due to the above overwrite may be due to the destruction of the initialization layer 16. Is considered to be high. This is because the initialization layer 16 is designed so that the magnetization does not reverse with normal laser power, but the magnetization of the initialization layer 16 may reverse for some reason.

Therefore, in this embodiment, when it is determined in step 46 that the error rate is smaller than the second reference value, the initialization layer 16 is initialized (step 47).
That is, the drive controller 25 lowers the number of revolutions of the spindle motor 22 as compared with normal recording and reproduction to improve apparent sensitivity, and the bias magnet control circuit 28.
The direction of the bias magnetic field of the bias magnet 24 is controlled in the direction opposite to that at the time of writing, and the light intensity of the laser light 23 emitted from the optical head 21 is set to the high power.

Therefore, at the time of this initialization, the directions of the laser power and the bias magnetic field are the same as those at the time of erasing by the above-mentioned normal method, but since the rotation speed of the magneto-optical disk 10 is lower than that at the time of erasing, The temperature of the laser light irradiation portion is raised to near the Curie temperature of the initialization layer 16. As a result, the first to third magnetic layers 13 to 15 reach the Curie temperature or higher, so that when the magnetization disappears and the temperature falls below the Curie temperature of the initializing layer 16, the initializing layer 16 has the same original bias magnetic field. It is magnetized in the initialization direction.

Then, when the temperature of the portion of the magneto-optical disk which has passed through the irradiation position of the laser beam falls below the Curie temperature of the second magnetic layer 14, the second magnetic layer 14 is magnetized in the same direction as the bias magnetic field. To be done. Thereafter, all four magnetic layers 13 to 16 are magnetized in the same direction as the bias magnetic field, that is, in the direction opposite to that in writing, similarly to the case of erasing by the normal method.

When the above initialization is completed, writing by overwriting is subsequently performed (step 48).
Writing by this overwriting makes the direction of the bias magnetic field of the bias magnet 24 opposite to that at the time of initialization or erasing, and when the light intensity of the radiated laser beam 23 of the optical head 21 is "1". When the power is high and the data is "0", it is modulated to low power.

Therefore, the write operation when the data is "1" is the same as the write operation by the normal method shown in FIG. 5, and the first magnetic layer 13 is indicated by the arrow in parentheses in FIG. 6 (D). As shown by, it is magnetized in the same direction as the bias magnetic field.

On the other hand, when the data is "0", a laser beam of a low power, which is smaller than the above high power but larger than the read power at the time of writing data "0" in the above-described normal method, is emitted. The magnetic disk is irradiated as schematically shown in FIG. As a result, the temperature of the portion irradiated with the laser light rises to near the Curie temperature of the first magnetic layer 13, and the magnetization of the third magnetic layer 15 disappears as schematically shown in FIG. When the temperature decreases after passing through the irradiation position, the first magnetic layer 13 is moved in the same direction as the second magnetic layer 14 due to the exchange coupling force of the second magnetic layer 14, as schematically shown in FIG. 6C. Is magnetized.

When the temperature further lowers and becomes equal to or lower than the Curie temperature of the third magnetic layer 15, the magnetization of the initialization layer 16 becomes as shown in FIG.
As schematically shown in (D), the third magnetic layer 15 and the second magnetic layer 15
Is transferred to the magnetic layer 14. In this way, data "0" is recorded in the first magnetic layer 13 as magnetization in the direction opposite to the bias magnetic field.

Therefore, at the time of overwriting, the bias magnetic field is fixed and the light intensity of the laser beam is modulated for recording, and at the end of data recording, as shown in FIG. 6D, the data is "0", "1". ”, The magnetic layers 14, 1
Since both 5 and the initialization layer 16 are magnetized in the same direction, overwriting can be performed many times.

Returning to FIG. 3 again, verification is performed after the above-mentioned writing by the overwrite is finished (step 49), and the error rate at that time is the third reference value (this is the first and second values). (It may be the same value as the reference value of 1 or different value may be different)) is determined (step 50). When the error rate is smaller than the third reference value, the initialization of the initialization layer 16 is normally performed,
Further, it is determined that the writing by the overwrite is normally performed, and this routine is ended (step 51).

On the other hand, when the error rate is equal to or higher than the third reference value, as in the case where it is determined in step 46 that the error rate is equal to or higher than the second reference value, the write failure is caused by the initialization layer 16. It is determined that it is due to a cause other than destruction, and a replacement process is performed using a separately provided replacement sector in place of the sector determined to be defective in writing (step 52), and the process ends (step 5).
3).

As described above, according to this embodiment, the first step 101 is realized in steps 41 to 44, and the second step is realized in steps 45 to 47. Since the destruction can be compensated and the initialization can be newly performed, the overwrite operation failure due to the destruction of the initialization layer 16 can be prevented.

The present invention is not limited to the above embodiment, and the direction of the bias magnetic field at the time of initialization is determined according to the composition of TbCo of the initialization layer 16.

[0049]

As described above, according to the present invention, since the initialization layer of the magneto-optical recording medium is initialized, it is possible to prevent the malfunction of overwriting due to the destruction of the initialization layer. The magnetic recording medium has features such as being large in that it contributes to improving the reliability of the magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a flowchart for explaining the principle of the present invention.

FIG. 2 is a block diagram of an example of a magneto-optical disk device used in the method of the present invention.

FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention.

FIG. 4 is an explanatory diagram of medium magnetization during normal erasing.

FIG. 5 is an explanatory diagram of medium magnetization during normal writing.

FIG. 6 is a diagram illustrating the principle of overwriting.

FIG. 7 is a cross-sectional structure of an example of a magneto-optical recording medium.

FIG. 8 is a sectional structure of another example of the magneto-optical recording medium.

[Explanation of symbols]

 10 magneto-optical disk 11 substrate 13 first magnetic layer 14 second magnetic layer 15 third magnetic layer 16 fourth magnetic layer 20 magneto-optical disk device 21 optical head 24 bias magnet 25 drive controller 28 bias magnet control circuit 29 Error rate judgment circuit

Claims (2)

[Claims] 1. A memory layer (13) used for recording and reproducing information, and an initialization layer (16) magnetized in one direction at all times.
And a plurality of layers (14, 15) formed between the memory layer (13) and the initialization layer (16) and using exchange coupling force, formed on at least a substrate (11). If the error rate is equal to or higher than the first reference value, erase is performed and then known data is written.
When the error rate is less than the second reference value by performing verification on the magneto-optical recording medium that has undergone the step (101) of step (101) and the first step (101) of the initialization layer (12). A method for initializing a magneto-optical recording medium, comprising a second step (102) of performing writing for initialization. 2. In the second step (102), the magneto-optical recording medium is rotated at a lower rotation speed than in recording, reproducing and erasing, and a bias magnetic field is recorded on the magneto-optical recording medium. 2. The method for initializing a magneto-optical recording medium according to claim 1, wherein high-power laser light is applied while being applied in a direction opposite to time.