JPH0479046A - Information recording method - Google Patents

Abstract

PURPOSE:To reduce power consumption by impressing a specified magnetic field on an information recording medium obtained by laminating 1st and 2nd magnetic layers, irradiating the medium with a light beam so that a temperature may rise to a fixed temperature, cooling it and holding information corresponding to the recorded information of the 1st magnetic layer in the 2nd magnetic layer. CONSTITUTION:The coercive force HC1 of the recording auxiliary layer 11 of a magneto-optical disk 4 is small at a room temperature and the Curie point temperature TC1 thereof is high, and the coercive force HC2 of the magnetic layer for recording 10 is larger than that of the layer 11 and the Curie temperature TC2 is low. By impressing the magnetic field which is larger than the force HC1 and smaller than the force HC2, the direction of magnetization of the layer 11 is adjusted and the magnetic layer is irradiated with the light beam so that the temperature of the magnetic layer is made to rise to a temperature which is higher than the temperature TC2 and lower than the temperature TC1. Then, the magnetic field smaller than the force HC2 is impressed corresponding to one of recorded information previously set. After the direction of the magnetization of the magnetic layer 11 is set to a direction corresponding to the recorded information, the magnetic layer is cooled and the information corresponding to the recorded information of the layer 11 is held in the layer 10. Thus, the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an information recording method for overwriting information on an information recording medium such as a magneto-optical disk.

[Prior Art] In recent years, magneto-optical disk devices using magneto-optical disks as recording media have attracted great expectations due to their large storage capacity and ability to be erased and rewritten. There is a lot of research going on to further improve performance (overwriting to increase data transfer speeds) and research to increase storage capacity.

As override methods, a magnetic field modulation method and an optical modulation method are known. The magnetic field modulation method is a method of applying a bias magnetic field modulated according to recorded information while irradiating a recording medium with a laser beam of constant intensity. The optical modulation method is a method in which a laser beam modulated according to recorded information is irradiated while applying a constant external magnetic field to a recording medium.

[Problems to be Solved by the Invention] However, in the above-mentioned magnetic field modulation method, the shape of the recording bit formed is feather-shaped, so there are problems such as fluctuations in the edge of the bit and bits remaining unerased during erasing. be. Furthermore, since the polarity of the magnetic field is switched in both positive and negative directions depending on the recording signal, the power consumption of the magnetic head increases.

On the other hand, in the optical modulation method, since the power of the semiconductor laser is controlled to three levels of power for erasing, recording, and reproduction, control of the semiconductor laser becomes complicated. Also, when overriding, two levels of power are required for erasing and recording, so
It was difficult to control the temperature distribution in the recording layer, and there was a problem with bit edge fluctuations.

The present invention was made to solve these problems, and its purpose is to reduce the power consumption of the magnetic head by half,
Moreover, it is an object of the present invention to provide an information recording method in which control of laser power can be simplified.

[Means for Solving the Problems] In order to achieve the above object, a first magnetic layer having a coercive force at room temperature of I(c+ and a Curie temperature of Tc1) and a first magnetic layer having a coercive force at room temperature greater than the above-mentioned Hc+. It has a coercive force Hc2,
A magnetic field greater than H61 and smaller than Hc2 is applied to an information recording medium formed by laminating a second magnetic layer having a Curie temperature T C2 lower than the T e1 to increase the magnetic field of the first magnetic layer. A process of aligning the direction of magnetization in a certain direction, a process of irradiating a light beam of a predetermined intensity to raise the temperature of the first and second magnetic layers to a temperature higher than the Tc2 and lower than the Tc1, and predetermined recording information. a step of applying a magnetic field in a constant direction smaller than Hc2 corresponding to one of the magnetic layers to change the direction of magnetization of the first magnetic layer to a direction corresponding to recorded information; There is provided an information recording method comprising the steps of cooling the second magnetic layer and retaining information corresponding to information recorded in the first magnetic layer in the second magnetic layer.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an information recording apparatus used in the information recording method of the present invention.

In FIG. 1, reference numeral 1 denotes a first magnetic head disposed close to the upper surface of the magneto-optical disk 4. As shown in FIG.

The first magnetic head 1 is composed of a permanent magnet, and initializes the magneto-optical disk 4 by applying a magnetic field to the magneto-optical disk 4 prior to the information recording device number. A second magnetic head 2 is placed opposite the optical head 3 with the magneto-optical disk 4 in between. The second magnetic head 2 is composed of an electromagnet and is driven by a magnetic head drive circuit 5. The magnetic head drive circuit 5 operates according to instructions from a control section (not shown).
Operates only when recording information. When recording information, the second
The magnetic head 2 applies or does not apply a magnetic field of a predetermined intensity to the magneto-optical disk 4 in accordance with the recording signal.
Record information.

The optical head 3 includes a semiconductor laser (not shown), an objective lens 6, and the like, and the semiconductor laser is driven by a laser drive circuit 7. When recording information, the semiconductor laser irradiates the magneto-optical disk 4 with laser light of a predetermined intensity simultaneously with the operation of the second magnetic head. Furthermore, during reproduction, the magneto-optical disk 4 is irradiated with a laser beam having an intensity lower than the recording power, and therefore the intensity of the laser beam is controlled to be binary, that is, the recording power and the reproduction power. This laser light is controlled by instructions from a control section (not shown).

The magneto-optical disk 4 has a protective and interference layer 9 on a transparent substrate 8.
This is a recording medium having a multilayer film structure in which a recording magnetic layer 10, a recording auxiliary layer 11, which is a magnetic layer for recording assistance, and a protective layer 12 are sequentially formed. FIG. 2 is a diagram showing the coercive force characteristics of the two magnetic layers 10 and 11 of this magneto-optical disk 4 with respect to temperature. Curve 13 is a characteristic of the recording auxiliary layer 11, whose coercive force Hc+ is relatively small at room temperature, and the Curie point temperature T
el has relatively high properties. Further, a curve 14 shows the characteristics of the recording magnetic layer 10, which has a larger coercive force Hcf at room temperature and a lower Curie temperature T than the recording aid M11. 2.

Further, T ea□ of the curve 13 is the compensation point temperature of the recording auxiliary layer 11 .

It is assumed that the magneto-optical disk 4 having such a configuration is moving in six directions indicated by arrows, as shown in FIG. Further, the light spot from the optical head 3 enters from the substrate 8 side, and the diameter of the light spot on the magnetic layer is about 1 μm. A servo system for scanning a desired track with this light spot can be performed by a conventionally well-known method.

Next, the information recording method of the present invention will be explained. first,
Initialization of the magneto-optical disk 4 will be explained with reference to FIG. Since the first magnetic head 1 is in a position ahead of the second magnetic head 2, when the magneto-optical disk 4 moves in the direction of arrow A, the first magnetic head 1 applies the initializing magnetic field first. is applied. Magnetic field strength H of the first magnetic head,
, , as shown in FIG. 2, Hct<H, +11<
It is set to be H82. That is, it is set to be larger than the coercive force of the recording auxiliary layer 11 at room temperature (and smaller than the coercive force Hc2 of the recording magnetic layer 10). Also, the direction of the magnetic field of the first magnetic head 1 is , 3rd
As shown in the figure, it is in the direction of arrow B. As a result, the direction of magnetization of the recording auxiliary layer 11 that has passed through the lower surface of the first magnetic head 1 is aligned in the direction of arrow B (upward), and initialization is performed. Note that the direction of magnetization of the recording magnetic layer 10 is not affected by the magnetic field of the first magnetic head and maintains the original direction of magnetization since its coercive force Hc2 is greater than H,11.

After initializing in this way, the magneto-optical disk 4 is
It reaches between the magnetic head 2 and the optical head 3. here,
Information is erased or recorded. First, the erasing operation will be explained using FIG. 4. Note that the second magnetic head 2 is not used during the erasing operation.

In FIG. 4, step 1 indicates the direction of magnetization of the recording magnetic layer 10 and the recording auxiliary layer 11 after initialization, which is the same as the state shown in FIG. 3. Next, step 2
, 3, a laser beam of a constant intensity is irradiated from the optical head 3,
Information on the recording magnetic layer 10 is erased. The temperature rise of the recording magnetic layer 10 due to the laser beam irradiation is T cz
< T w < T c +, and in step 2, the temperature T w of the recording magnetic layer 10 is set to T w < T c +.
3 and T camp. In this state, since the Curie temperature T(2) is exceeded, the magnetization of the recording magnetic layer 10 becomes zero, and the old magnetization is erased.Step 3
Then, the temperature rises further and To. . and Tc+. In this state, the compensation temperature Tc of the recording auxiliary layer 11
, , , p is exceeded, so the direction of magnetization of the recording auxiliary layer 11 is reversed.

Step 4 is that the temperature of the central bit P2 is T, and T ct
The temperature of bits p, , p, on both sides is T c6
It is in a state between m9 and T. During erasing, no magnetic field is applied as described above, so the magnetization direction of each bit remains as in step 3. Step 5 shows a state where the optical head 3 is passed and cooling begins, and when the temperature of the recording auxiliary layer 11 falls below Tea, . . . p, the direction of magnetization is reversed again. Step 6 shows a state in which the temperature has been further cooled down to room temperature. Here, the recording magnetic layer 10
Since the temperature drops below the Curie temperature TC2, magnetization appears again, and its direction corresponds to the direction of magnetization of the recording auxiliary layer 11. In this example, the magnetization direction of the recording magnetic layer 10 is opposite to the magnetization direction of the recording auxiliary layer 11, but this depends on the characteristics of the medium. Therefore, by selecting a medium, the directions of magnetization can be made to be the same. As a result, the magnetization direction of the recording magnetic layer 10 is aligned in a certain direction, and old information is erased.

Next, the information recording operation will be explained with reference to FIG. Note that in FIG. 5, steps 1 to 3 are the same as the erasing operation, so the explanation of those steps will be omitted and the explanation will start from step 4.

Step 4 is that the temperature of the center bit P2 is between Tcoyo and Tct, and the temperature of the bits PP on both sides is T
It is between eo□ and Tw. Moreover, in step 4, the second
H.

A magnetic field of is applied in the B direction. This magnetic field is applied according to the recording signal, and is applied only when the recorded information is 1°, for example, and is not applied when the recorded information is 0°. Note that, as shown in FIG. 2, the magnetic field Hw is smaller than the coercive force H61 of the recording auxiliary layer 11 at room temperature. In step 4, since the temperature of the central pit P2 is between Tw and Tc+, when the magnetic field Hw is applied, the direction of magnetization of only that bit P2 is reversed and it faces in the B direction. In step 5, cooling begins as well as erasing, and T cam
When cooled to between p and T el, bits P1-P3
The direction of magnetization of each is reversed. In step 6, the recording magnetic layer 10 is cooled to room temperature, and magnetization appears in the recording magnetic layer 10 corresponding to the direction of magnetization of the recording auxiliary layer 1. Through the above steps, new information is recorded in the recording magnetic layer 10, and the override is completed.

Note that when reproducing, scanning is performed with a laser beam of lower power than during recording, and the temperature at this time may be approximately TR as shown in FIG.

In this embodiment, when recording information, the laser power may be constant, and there is no need to modulate the intensity according to the recording signal as in the conventional optical modulation recording method. Therefore, the laser power may be controlled to two values during recording and reproduction. Further, the second magnetic head 2 only needs to apply a magnetic field to one side of the recorded information, and does not need to generate bipolar magnetic fields corresponding to the recorded signals as in the conventional magnetic field modulation method. Therefore, the driving power for the magnetic head can be halved compared to the magnetic field modulation method. Furthermore, in this embodiment, the shape of the recording pit is not a feather-like shape as in the magnetic field modulation method, but a circular or elliptical shape.

FIGS. 6 and 7 each show other configuration examples of magneto-optical disks used in the present invention, and FIG. 8 shows the coercive force characteristics of each layer with respect to temperature in these disks.

FIG. 6 shows a configuration of the magneto-optical disk shown in FIG. 1 in which an exchange force adjusting layer 15 is arranged between the auxiliary recording layer 11 and the recording magnetic layer 100. The coercive force Hc3 and Curie temperature Tcz of this layer at room temperature have characteristics as shown by curve 16 in FIG. This layer is magnetized in the in-plane direction at room temperature, and when the temperature rises due to the power of the optical spot during recording,
It has a characteristic that it has perpendicular magnetization that is the same as the direction of magnetization of the recording auxiliary layer 11, or that its magnetization disappears. This serves to weaken the exchange coupling force between the recording auxiliary layer 11 and the recording magnetic layer 10 at room temperature. Therefore, the strength of the magnetic field during recording can be increased to
It can be lowered to the r side.

In the case shown in FIG. 7, a reproducing layer 17 is further arranged between the recording magnetic layer 10 and the protective/interference layer 9 having the structure shown in FIG. As mentioned above, the Kerr rotation angle due to the Kerr effect during reproduction is larger for a magnetic layer with a higher Curie temperature. Therefore, the coercive force Hc4 of the reproducing layer 17 and the Curie temperature T
C4 has a characteristic as shown by curve 18 in FIG. In this reproducing layer 17, perpendicular magnetization corresponding to the magnetization of the pits of the recording magnetic layer 10 appears due to the exchange coupling force with the recording magnetic layer 10 at a temperature raised by the power of the optical spot during reproduction. Since the reflection of light during reproduction is mostly affected by the reproduction layer 17, the Kerr rotation angle is thicker than when it is reflected by the recording magnetic layer 10.

Up to Uni, the characteristics of the recording auxiliary layer 11 and the recording magnetic layer 10 are as shown in FIG.
We have explained the case where there is a compensation point (curve 1813) and the recording magnetic layer 10 has no compensation point (curve 14).
The configuration shown in FIG. 6 or 7 may have the characteristics shown in FIGS. 9 to 11. Here, FIGS. 9, 10, and 11 respectively show the recording auxiliary layer 11 (curve 13
Neither the recording magnetic layer 10 (curve 14) has a compensation point, the recording auxiliary layer 11 (curve 13゛) does not have a compensation point, but the recording magnetic layer 10 (curve 14゛) does not have a compensation point. In addition, both the recording auxiliary layer 11 (curve 13) and the recording magnetic layer 10 (curve 14') have compensation points.

As a specific material for each layer of the magnetic layer group, an amorphous alloy made of a combination of one or more of each of a transition metal and a rare earth metal can be used. For example, transition metals are mainly Fe, Go, and Ni, and rare earth metals are mainly Gd,
There are Tb, Dy, Ho, Nd, and Sm. Typical combinations include TbFeCo, GdTbFe
, GdFeC.

Examples include GdTbFeCo and GdDyFeCo.

Further, the material of the recording auxiliary layer is Co-Cr based, Ba-F
errite series, MnB1 series, iron oxide series, Co-doped iron oxide series, CrL series, N1-Co series, Fe-Ni-C
It may be a magnetic material such as o-based or a Heusler alloy such as PtMnSb.

The substrate 8 is made of a glass material, a plastic material such as polycarbonate (PC), or polymethyl methacrylate (PMMA), and may be thick (hard) or thin (flexible).

The present invention can be applied in various ways in addition to the embodiments described above. For example, although a magneto-optical disk has been described in the embodiment, a card-shaped or tape-shaped medium can also be used.

[Effects of the Invention] As explained above, according to the information recording method of the present invention, it is only necessary to control the laser power to two values, one for override and one for reproduction. The configuration can be significantly simplified. In addition, since the magnetic head only needs to operate to determine whether or not to apply a magnetic field in one direction, the power consumption can be halved and the structure can be reduced compared to magnetic heads used in conventional magnetic field modulation methods. Can be simplified. Furthermore, since the shape of the recording bit is circular or oval, there is an effect that the quality of the reproduced signal can be improved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an information recording apparatus according to the present invention, FIG. 2 is a characteristic diagram of a magneto-optical disk used in the present invention, FIG. 3 is an explanatory diagram showing the initialization operation of the magneto-optical disk, and FIG. FIG. 5 is an explanatory diagram showing the information erasing operation, FIG. 5 is an explanatory diagram showing the information recording operation, FIGS. 6 and 7 are sectional views each showing other examples of magneto-optical disks, and FIG. , a diagram showing the characteristics of the magneto-optical disk in FIG. 7, FIGS. 9, 10, and 11.
The figures show other characteristics of the magneto-optical disks shown in FIGS. 6 and 7, respectively. 1: First magnetic head 2; Second magnetic head 3, optical head 4. Magneto-optical disk 5: Magnetic head drive circuit 7: Laser drive circuit 8: Transparent substrate 11: Recording auxiliary layer 10/recording magnetic layer FIG.

Claims (1)

[Claims] The coercive force at room temperature is H_c_1 and the Curie temperature is T_c
The first magnetic layer has a coercive force of H_1 at room temperature, and the coercive force at room temperature is H_1.
The above-mentioned H
A process of applying a magnetic field greater than _c_1 and smaller than H_c_2 to align the direction of magnetization of the first magnetic layer in a certain direction, and irradiating the first and second magnetic layers with a light beam of a predetermined intensity.
In the process of increasing the temperature of the first magnetic layer to a temperature higher than T_c_2 and lower than T_c_1, a magnetic field smaller than H_c_2 in a certain direction corresponding to one of the predetermined recording information is applied to increase the temperature of the first magnetic layer. a process of changing the direction of magnetization to correspond to recorded information; a process of cooling the first and second magnetic layers and retaining information corresponding to the recorded information of the first magnetic layer in the second magnetic layer; An information recording method characterized by: