JP2602107B2 - Magneto-optical recording device - Google Patents

Description

The present invention relates to a first magnetic layer for recording information, a second magnetic layer formed on the first magnetic layer, and a second magnetic layer formed on the second magnetic layer. Proposed a magneto-optical recording apparatus for recording information on a magneto-optical recording medium in which four magnetic layers of a formed third magnetic layer and a fourth magnetic layer formed on the third magnetic layer are stacked. Is what you do.

[Conventional technology]

FIG. 6 is a conceptual diagram of the operation of recording and erasing information on this type of magneto-optical recording medium. The magneto-optical recording medium 1 shown in FIG. 6 (b) has, on a substrate 11 made of, for example, glass, a first magnetic layer 12 having perpendicular magnetic anisotropy and capable of reversing the magnetization direction;
The first magnetic layer 12 is formed by laminating a second magnetic layer 13 having perpendicular magnetic anisotropy, being magnetized in one direction, and having a magnetization direction which cannot be reversed under the same conditions as the first magnetic layer 12. ing.

When recording and erasing information on the magneto-optical recording medium 1 by the recording signals "1" and "0" shown in FIG. 6A, the magneto-optical recording medium 1 is rotated and the A downward external magnetic field + H indicated by a black arrow opposite to the magnetization direction of the two magnetic layers 13 is applied. Then, in the period of the recording signal is "1" for projecting a light beam LB of the projection direction indicated by the outline arrow of high power P _H as shown in Figure No. 6 (c) to the first magnetic layer 12. Then, when the first magnetic layer 12 is heated by the light beam LB to reach the Curie temperature, the magnetization direction of the first magnetic layer 12 is reversed in the same direction as the external magnetic field + H, that is, in the direction of the substrate 11, and the magneto-optical recording medium When the light beam LB is not projected by the rotation of 1 and the temperature of the first magnetic layer 12 decreases, the first magnetic layer 12 is magnetized in the direction of the substrate 11 to record information. In the period of the recording signal is "0" that projects a light beam LB for low output P _L as shown in Figure No. 6 (c) to the first magnetic layer 12. As a result, the coercive force of the first magnetic layer 12 is reduced, and the magnetization is reversed in the same direction as the magnetization direction of the second magnetic layer 13, that is, magnetized in the direction opposite to the substrate 11 to erase information.

When recording and erasing information on the magneto-optical recording medium 1 as described above, a magnetic field having a direction opposite to the magnetization direction of the second magnetic layer 13 is applied from the outside, and the light beam LB is changed to a high output P _H and a low output P _L. I do. In the case of reproducing the recorded information, to further lower the reproducing light output P _R than the low output P _L.

On the other hand, a magneto-optical disk in which four magnetic films are laminated is disclosed in Japanese Patent Application Laid-Open No. 63-268103. In this magneto-optical disk, the Curie temperature of the magnetic film is
150 ° C, 210 ° C for the second magnetic film, 150 ° C for the third magnetic film, 4th
The temperature of the magnetic film is 130 ° C.

[Problems to be solved by the invention]

In the above-described conventional magneto-optical recording apparatus, the light output of the light beam projected on the magneto-optical recording medium is kept constant with respect to the ambient temperature of the magneto-optical recording medium regardless of its change. Therefore, the heating temperature of the magneto-optical recording medium due to the projection of the light beam is substantially proportional to the ambient temperature under the influence of the ambient temperature.

Therefore, when the ambient temperature of the magneto-optical recording medium is high, when recording and erasing information, the magneto-optical recording medium is heated more than necessary, and the recorded and erased information area is enlarged, thereby recording and erasing information. There is a problem that accuracy is reduced and reliability of recorded information is reduced.

When recording and erasing information by the above-described conventional magneto-optical storage device, the magnetic layer to which the magneto-optical recording medium is coupled by exchange force increases the temperature of the magneto-optical recording medium during the process of recording and erasing information. Depending on the case, the magnetization direction may be reversed. Further, in a conventional magneto-optical disk in which four magnetic layers are stacked, the Curie temperature of the second magnetic film is higher than the Curie temperature of the third magnetic film, so that the third magnetic film functions as an initialization layer. It cannot be used sufficiently, and there is a problem in the accuracy of recording and erasing information.

In view of such a problem, the present invention enables recording and erasing of information without being affected by the ambient temperature of the magneto-optical recording medium on which information is recorded and erasing. It is an object to provide a magneto-optical recording device that can be enhanced.

[Means for solving the problem]

The magneto-optical recording device according to the present invention has a first
A magnetic layer, a second magnetic layer formed on the first magnetic layer, a third magnetic layer formed on the second magnetic layer, and a light beam projection formed on the third magnetic layer. And a fourth magnetic layer, which is an initialization layer in which the magnetization is not reversed by the temperature rise due to the temperature rise, the adjacent magnetic layers are coupled by an exchange force, and the Curie temperature of the i-th (i = 1 to 4) magnetic layer is reduced. _Assuming that T _Ci , a temperature detector that detects the ambient temperature of the magneto-optical recording medium that satisfies the relationship of T _C4 > T _C2 > T _C1 > T _C3 > room temperature, and the temperature detected by the temperature detector Means for obtaining an optimum optical output of a light beam, wherein the optical modulation direct overwrite is performed on the magneto-optical recording medium.

[Action]

In the present invention, the optimum optical output of the light beam projected onto the magneto-optical recording medium is determined based on the detected ambient temperature of the magneto-optical recording medium having the four magnetic layers. The magneto-optical recording medium is
Adjacent magnetic layers are coupled by exchange force, and the i-th (i
= 1 to 4) The relationship of T _C4 > T _C2 > T _C1 > T _C3 > room temperature is established with the Curie temperature of the magnetic layer being T _Ci , and the fourth magnetic layer has the highest Curie temperature and the light beam Does not reverse the magnetization direction due to the temperature rise due to the projection of the magnetic field, and opposes the bias magnetic field. The third magnetic layer blocks the exchange force from the fourth magnetic layer in a high temperature range. At room temperature, the magnetization direction of the first magnetic layer is not reversed due to the magnetization reversal of the second magnetic layer, and the magnetization directions of the second magnetic layer and the third magnetic layer are aligned with the magnetization direction of the fourth magnetic layer at room temperature after information recording.

Thus, when the light output of the light beam is optimally controlled in accordance with the ambient temperature of the magneto-optical recording medium during information recording, the fourth
The magnetization direction of the magnetic layer does not reverse due to the temperature rise, and the function of the initialization layer can be sufficiently exhibited.

Thus, the light output of the light beam changes in relation to the ambient temperature of the magneto-optical recording medium, and the heating temperature of the magneto-optical recording medium is not affected by the ambient temperature.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings showing examples.

FIG. 1 is a block diagram showing a main part of a magneto-optical recording device according to the present invention. When the magneto-optical recording medium 1 is loaded with a magneto-optical recording device, an external magnetic field (not shown) is applied to the magneto-optical recording medium 1, and an optical output related to a recording signal from a semiconductor laser 5, which will be described later. When the light beam is projected, information is recorded and erased in the information recording area 1a of the magneto-optical recording medium 1. Temperature detector 2 provided to detect the ambient temperature of magneto-optical recording medium 1
Flows the current of a constant current source 21 to a temperature-sensitive resistor 22 such as a thermistor, and detects the ambient temperature of the magneto-optical recording medium 1 by a voltage drop generated in the temperature-sensitive resistor 22. The terminal voltage of this temperature sensitive resistor 22 is
And converted into a digital signal. The digital signal is converted into a CP in the optical output operation unit 3 including the CPU 31 and the ROM 32.
Given to U31. The ROM 32 stores, for example, information on the optimum light output of the light beam for each ambient temperature, or the optimum light output at room temperature and a temperature coefficient for obtaining the optimum light output for each ambient temperature based on the room temperature. In addition, calculation contents for obtaining the optimum light output of the light beam are stored, and those recorded contents are given to the CPU 31. The output of the light output operation unit 3 as the output of the CPU 31 is supplied to the light output control unit 4, and the output is supplied to the semiconductor laser 5. The output of the light detector 6 that detects the light output of the semiconductor laser 5 is provided to the light output control unit 4. The light output control unit 4 controls the light output of the semiconductor laser 5 according to the output of the light output calculation unit 3, and the light detector 6 detects the light output of the semiconductor laser 5 and responds to the detected output. The optical output of the semiconductor laser 5 is corrected for a minute change to stabilize the optical output.

Next, the operation of the magneto-optical recording device thus configured is
The control content of 1 will be described with reference to the flowchart shown in FIG.

When the magneto-optical recording medium 1 is loaded into the magneto-optical recording apparatus in order to record and erase information on the magneto-optical recording medium, an analog signal relating to the ambient temperature of the magneto-optical recording medium 1 detected by the temperature detector 2 is converted into an analog signal. Digital (A / D) converter 23
Is converted to a digital signal by the CPU 31
(S1). The contents stored in the ROM 32 are input to the CPU 31. The CPU 31 obtains an optimum optical output corresponding to the detected ambient temperature based on, for example, the optimal optical output for each ambient temperature and the calculation content for obtaining the optimal optical output input from the ROM 32 (S2). Then, a signal for instructing the obtained optimum light output is given to the light output controller 4 (S3). Then, the light output control unit 4 drives the semiconductor laser 5 to obtain the commanded optimum light output. The optical output of the semiconductor laser 5 is maintained at an optimum value at the ambient temperature of the magneto-optical recording medium 1. Further, a minute change in the light output of the semiconductor laser 5 is corrected by the output of the photodetector 6 for detecting the light output of the semiconductor laser, so that the light output of the semiconductor laser 5 is stabilized.

When the optical output of the semiconductor laser 5 is controlled in this way and information is recorded or erased on the magneto-optical recording medium 1 by a recording signal, the optical output changes as shown in FIG.

That is, in the recording / erasing time range A in the operation state shown in FIG. 3C, when a recording signal as shown in FIG. 3B is given, the ambient temperature of the magneto-optical storage medium 1 is, for example, normal temperature. In the case of T ₀ , it changes as shown by the solid line in FIG. That is, the light output of the semiconductor laser 5 when the recording signal is "1" goes high output P _H, when the "0" low output
It becomes P _H.

On the other hand, when the ambient temperature is higher temperatures T ₁ than the room temperature T _0, the light output of the semiconductor laser 5 when the recording signal as indicated by a broken line is "1" becomes a high power P _H ',' 0 In the case of "", the output becomes low P _L '.

The light output of the light beam at the time of information reproduction will further low regeneration optical output P _R than the low output P _L 'that is constant regardless of the ambient temperature. The ambient temperature in the high temperature T ₁ of from ambient temperature ambient temperature T ₀
Lowering the heating temperature by the light beam reduces the light output of the light beam in accordance with the temperature difference between T ₀ and the high temperature T ₁ of from room temperature. Therefore, the heating temperature of the magneto-optical recording medium 1 due to the projection of the light beam always has an appropriate value without being affected by the ambient temperature of the magneto-optical recording medium 1.

Therefore, even if the ambient temperature of the magneto-optical recording medium 1 changes, information can always be properly recorded and erased, and the reliability of recorded information can be improved.

FIG. 4 is an explanatory diagram for further explaining the magneto-optical recording medium 1 shown in FIG.

This magneto-optical recording medium 1 is, for example, a substrate made of glass.
On the dielectric layer 40A, a recording layer 40B, a recording auxiliary layer 40C, a control layer 40D, an initialization layer 40E, and a protective layer 40F are laminated in this order on the dielectric layer 40A. The recording layer 4
0B (first layer) and the initialization layer 40E (fourth layer) are the first magnetic layer 12 and second magnetic layer 13 of the magneto-optical recording medium having the above-described first magnetic layer 12 and second magnetic layer 13. Has the same function as.

Each of the layers is formed by, for example, a sputtering method using the materials and thicknesses shown in Table 1.

These magnetic layers have the following characteristics. Adjacent magnetic layers are connected by exchange force. Recording layer (first layer)
40B records and holds information. Recording auxiliary layer (second layer) 4
0C, the control layer (third layer) 40D and the initialization layer (fourth layer) 40E do not have a function of retaining information, and are additional layers that enable light modulation direct overwrite. When the temperature rises due to laser irradiation, the sublattice magnetization does not reverse in the temperature range, but acts against the bias magnetic field.
The control layer 40D acts to block the exchange force from the initialization layer 40E in a high temperature range.

Here, T _C1 is the Curie temperature of the i-th layer (where i = 1 to 4), H _C1 is a magnetic field width (corresponding to coercive force) of half of the reversal magnetic field of the i-th layer, and H _W1 is Exchange force received by the i-th layer from the layer (the transition width of the loop of the i-th layer;
The third layer is defined for magnetization reversal as shown in FIG. 5).

FIG. 5 shows a conceptual diagram of the sublattice magnetization. Here, assuming that the i-th layer is a third layer, for example, the upper and lower layers,
The directions of magnetization of the fourth layer and the third layer are as shown in FIG. 5 (a) or (b). Also, as shown in FIG. 5 (a), when the direction of magnetization of the (i-1) th layer and the direction of magnetization of the (i + 1) th layer are directions away from each other, the direction of magnetization of the (i) th layer is i-th layer. The state is directed to the first layer or the (i + 1) th layer.
On the other hand, when the direction of magnetization of the (i-1) th layer and the direction of magnetization of the (i + 1) th layer are close to each other as shown in FIG. 5 (b), the direction of magnetization of the (i) th layer is the (i + 1) th layer. Or the i-th
It is in a state of facing one layer.

When defined in this way, the magnetization characteristics are: T _C4 > (Tcomp ₄ )> T _C2 > T _C1 > (Tcomp ₂ )> T _C3 > room temperature
(1) Recording layer 40B: H _W1 <H _C1 : up to room temperature... (2) H _W1 > H _C1 : up to T _C1 (3) Recording auxiliary layer 40C: H _W2 > H _C2 : up to T _C3 . … (4) H _W2 <H _C2 : ∼T _C1 …… (5) Control layer 40D: H _W3 > H _C3 : ∼T _C3 …… (6) Initialization layer 40E: H _W4 <H _C4 : _∼Operating temperature Within the range (7) (where Tcomp ₂ and Tcomp ₄ are the compensation temperatures of the second and fourth layers). According to the equation (2), the magnetization direction of the recording layer 40B is the magnetization reversal of the recording auxiliary layer 40C at room temperature. Not inverted by (4),
In the equations (6) and (7), the recording auxiliary layer 40 is recorded at room temperature after recording.
C indicates that the magnetization directions of the control layer 40D and the initialization layer 40E are aligned downward.

The magneto-optical recording medium having four magnetic layers can exhibit good performance when the light output of the light beam is precisely controlled with respect to the ambient temperature of the magneto-optical recording medium during recording. Thus, the magneto-optical recording device of the present invention can sufficiently exhibit its characteristics when recording and erasing information on a magneto-optical recording medium having four magnetic layers.

In this embodiment, the magneto-optical recording apparatus has been described. However, the same effect can be obtained in a magneto-optical recording and reproducing apparatus capable of recording and reproducing information.

〔The invention's effect〕

As described in detail above, when the ambient temperature of a magneto-optical recording medium having four magnetic layers changes, the magneto-optical recording device of the present invention projects the light projected onto the magneto-optical recording medium in accordance with the change. The light output of the beam changes. Therefore, the heating temperature of the magneto-optical recording medium by the light beam is always maintained at an appropriate value, and information can be accurately recorded and erased without being affected by the ambient temperature, and an excellent effect of improving the reliability of recorded information is achieved.
Such an effect is obtained by providing a magneto-optical recording medium having four magnetic layers coupled by an exchange force, and the fourth magnetic layer does not reverse its magnetization direction due to a temperature rise in the process of recording and erasing information. This is particularly remarkable when the layer is an initialization layer and performs direct overwriting.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a magneto-optical recording apparatus according to the present invention, FIG. 2 is a flowchart showing control contents of a CPU, and FIG. 3 shows a change state of a light output of a light beam with respect to a recording signal. FIG. 4 is a timing chart, and FIG. 4 is an explanatory diagram for further describing the magneto-optical recording medium shown in FIG.
FIG. 6 is a conceptual diagram of sublattice magnetization, and FIG. 6 is a conceptual diagram of an operation of recording and erasing information by a conventional magneto-optical recording device. DESCRIPTION OF SYMBOLS 1 ... Magneto-optical recording medium, 2 ... Temperature detector, 3 ... Optical output operation part, 4 ... Optical output control part, 5 ... Semiconductor laser,
6 photodetector, 12 first magnetic layer, 13 second magnetic layer, 22 temperature-sensitive resistance, 40B recording layer, 40C recording auxiliary layer, 40D control layer, 40E ... Initialization layer In the drawings, the same reference numerals indicate the same or corresponding parts.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kunimaro Tanaka 8-1-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Inside the Industrial Systems Research Laboratories, Mitsubishi Electric Corporation (72) Inventor Yasuhiro Kiyose 8-1, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. 1 Inside Mitsubishi Electric Corporation Industrial Systems Research Institute (72) Inventor Yoshiyuki Nakagi 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Inside Mitsubishi Electric Corporation Industrial Systems Research Institute (72) Inventor Teruo Furukawa Amagasaki City, Hyogo Prefecture 8-1, 1-1 Tsukaguchi Honmachi Mitsubishi Electric Corporation Industrial System Research Laboratory (56) References JP-A-63-237238 (JP, A) JP-A-62-175230 (JP, A) JP-A-61-214266 ( JP, A) JP-A-62-167641 (JP, A) JP-A-58-73017 (JP, A)

Claims (1)

(57) [Claims] 1. A magneto-optical recording apparatus for recording and erasing information on a magneto-optical recording medium in relation to the light output of a light beam projected on the magneto-optical recording medium, comprising: a first magnetic layer for recording information; A second magnetic layer formed on the first magnetic layer, a third magnetic layer formed on the second magnetic layer, and a magnetization formed on the third magnetic layer depending on a temperature rise caused by the light beam projection. And a fourth magnetic layer, which is an initialization layer that does not invert, the adjacent magnetic layers are coupled by exchange force, and the Curie temperature of the i-th (i = 1 to 4) magnetic layer is T _Ci , A temperature detector for detecting the ambient temperature of the magneto-optical recording medium satisfying the relationship of T _C4 > T _C2 > T _C1 > T _C3 > room temperature, and the optimum light of the light beam based on the temperature detected by the temperature detector Means for obtaining an output, and performing optical modulation direct overwrite on the magneto-optical recording medium. Magneto-optical recording apparatus characterized that you have to configure.