JPH04113532A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To dispense with magnets for initialization and bias magnets on overwriting by specifying the relation of Curie temps. of first to third magnetic layers and specifying the stray magnetic fields of the second and third magnetic layers to the first magnetic layer. CONSTITUTION:On a substrate 11, a first magnetic layer 12 having a magneto- optical effect, dielectric layer 13, antiparallel type second magnetic layer 14 having perpendicular magnetic anisotropy, and third magnetic layer 15 are successively formed. These three magnetic layers are formed to satisfy the relation Tc1<Tc2<Tc3, when Tc1, Tc2, and Tc3 are Curie temps. of the first, second and third magnetic layers 12, 14, 15 respectively, and relations Hd2 Hd3 at room temp., Hd2>Hd3 at near Tc1 and Hd2<Hd3 at temp. from Tc2 to Tc3, when Hd2 and Hd3 are the stray magnetic fields of the second magnetic layer 14 and third magnetic layer 15, respectively, to the first magnetic layer 12. In this case, by varying the power of laser light 16 according to the informa tion data to be recorded on overwriting, magnetic recording according to the information data to be recorded can be performed by using changes of the stray magnetic fields. Thereby, no initialization magnet nor bias magnet is required.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an overwriteable magneto-optical recording medium.

(B) Conventional technology Conventionally, magneto-optical recording media that can be overwritten (overwritten) using optical modulation methods have been proposed as shown in FIGS. Japanese Journalof,A
pplied Physics, ~o1.26 (198
7) Supplement 26-4. P2S5-15
9).

That is, as shown in FIG. 5, the magneto-optical recording medium 1 uses a laser beam 2 and the magnetic field of a magnet 3.4 to record or overwrite information at high density, and uses the laser beam 2 to generate the Kerr effect. The recorded information is read out. As shown in FIG. 6, this magneto-optical recording medium 1 consists of a recording layer 5 and an auxiliary layer 6 on a substrate. , H+ > Ht,
The material is selected to have the relationship T + < T t. The relationship between the temperature of the medium 1 and the strength of the magnetic field is expressed in the seventh
As shown in the figure.

In FIG. 7, Tr is room temperature, and Hb is the strength of the magnetic field of the bias magnet.

When recording on the recording layer 5, for example, when rewriting recorded data, a bias magnet 3 and an initialization magnet 4 that generate a magnetic field in the opposite direction to the bias magnetic field are provided. The magnitude H1 of the magnetic field from the initialization magnet 4 is smaller than the coercive force H1 of the recording layer 5 and larger than the coercive force H2 of the auxiliary layer 6. During recording on the recording layer 5, this initializing magnetic field is always applied to the rotating medium 1, so when the medium 1 rotates in the direction of arrow 8 in the figure, the auxiliary layer 6 is activated by the initializing magnet 4. The initialization magnet 4 is magnetized in the direction of magnetization, that is, downward in the drawing.

Overriding is performed by irradiating high power and low power laser beams in accordance with the recorded information data 9. That is, when irradiating with a low power laser beam, the temperature of the medium 1 is set higher than the Curie temperature T1 of the recording layer 5, and the Curie temperature T of the auxiliary layer 6 is lower. The power of the laser beam is adjusted so that the Curie temperature T of the layer 6 becomes higher.

Therefore, during low power irradiation, the magnetization of the recording layer 5 becomes zero, but since the magnetization of the auxiliary layer 6 remains, exchange coupling from the auxiliary layer 6 occurs during cooling after the laser light irradiation is stopped. Due to the force, the recording layer 5 is magnetized in the same direction as the auxiliary layer 6 (in the same direction as the initialization magnetic field). On the other hand, during high-power irradiation, the magnetization of both the recording layer 5 and the auxiliary layer 6 becomes zero, so when the two layers are cooled down after the laser beam irradiation is stopped, the auxiliary layer 6 initially absorbs the magnetic field from the bias magnet 3. Then, the recording layer 5 is also magnetized in the same direction.

In this way, the recording layer 5 is magnetized in the direction of the initialization field by low power irradiation and in the direction of the bias field by high power irradiation.

(c) Issues to be solved by the invention: Since a magneto-optical recording medium that can be overridden by the conventional optical modulation method is composed of a recording layer and an auxiliary layer, an initializing magnet is required during overriding. This method requires a bias magnet and a disadvantage that the recording device becomes complicated.

The present invention was devised in view of the above points, and an object of the present invention is to provide a magneto-optical recording medium that does not require an initialization magnet or a bias magnet at the time of overriding.

(d) Means for Solving the Problems In order to solve the problems, the magneto-optical recording medium according to the present invention includes a first magnetic layer having a magneto-optic effect, a dielectric layer, and a perpendicular magnetic anisotropy on a substrate. A second magnetic layer and a third magnetic layer of an anti-parallel type having orientation are sequentially laminated, and the first
The third magnetic layer has its Curie temperature Tc+, Tc,
, Tc, then Tc1<Tc, <Tc,
Further, when the magnitude of the stray magnetic field of the second magnetic layer and the third magnetic layer with respect to the first magnetic layer is I(d,,Hd,), at room temperature, Hd, #Hd,,Tc, and in the vicinity, Hd, >Hd, , T
In the temperature range from c2 to Tc, the relationship is Hd<)ld.

(e) At the time of effect override, stray magnetic fields from the second and third magnetic layers during laser beam irradiation are utilized. Also,
The laser beam is used with its power adjusted to high power and low power according to the recorded information data.This low power irradiation increases the Curie temperature Tc of the first magnetic layer,
The magneto-optical recording medium is heated to a temperature in the vicinity, and the high-power irradiation heats the magneto-optical recording medium to a temperature in the range of the Curie temperature Tc of the second magnetic layer and the Curie temperature Tc of the third magnetic layer. The power of each is adjusted accordingly.

On the other hand, since the second magnetic layer and the third magnetic layer are anti-parallel, the direction of the stray magnetic field exerted by these magnetic layers on the first magnetic layer is different, and Tc at the time of low-power laser beam irradiation is different from that in the vicinity. Since Hd, > Hd, the first
When the magnetic layer is cooled, it is magnetized in the direction of the stray magnetic field Hd by the exchange coupling force of the stray magnetic field Hd of the second magnetic layer. On the other hand, during high-power irradiation with laser light, the magneto-optical recording medium is heated to a temperature in the range of Cunot temperatures TCI and Tc, and since Hd2<Hd3 in this temperature range, the first magnetic layer is cooled. Sometimes the stray magnetic field H of the third magnetic layer
Due to the exchange coupling force of d, it is magnetized in the direction of its stray magnetic field Hd s.

Therefore, when overriding, there is no need for a bias magnet, which was required in the past.

(f) Example An embodiment of the present invention will be described based on the drawings.

FIG. 1 is a schematic sectional view of a magneto-optical recording medium according to the present invention, conceptually showing the state of overriding.

In this drawing, a magneto-optical recording medium 10 includes a transparent substrate 1
1, a first magnetic layer 12 having a magneto-optical effect, a dielectric layer 13, and a second and third magnetic layer 14 and a third magnetic layer 15 of an anti-parallel type having perpendicular magnetic anisotropy are sequentially laminated. configured. These magnetic layers have their Curie temperatures Tct,
When Tct and Tcs, Tct<Tc and <Tct, and when the magnitude of the stray magnetic field of the second magnetic layer 14 and third magnetic layer 15 with respect to the first magnetic layer 12 is Hd, , Hd, The relationship Hd t≠Hd at room temperature, Hd = > Hd s near Tc+, and Hd = <Hd h in the temperature range from Tct to Tc is used.

Specifically, a glass plate or polycarbonate street resin with a thickness of 1.2 mm is used as the transparent substrate 11, and each magnetic layer is made of rare earth metal elements (Gd, Tb, etc.) and transition metal elements (Fe, Co, etc.). , and each magnetic layer is formed by sputtering the material. In this embodiment, the first magnetic layer 12 is T.
TbFeCo was used as the second magnetic layer 13 and the third magnetic layer 14.

In this case, the direction and magnitude of magnetization appearing externally from each part of the amorphous alloy is determined by the spin direction and magnitude of the rare earth metal atoms within the amorphous alloy and the spin direction and magnitude of the transition metal atoms. By setting the composition ratio of the element Tb to 26 to 27%, a compensation composition can be obtained in which the spin direction and magnitude of the rare earth metal atoms in the amorphous alloy are almost equal to the spin direction and magnitude of the transition metal atoms. . In addition, in each composition of the two magnetic layers, when the rare earth metal element in both layers is more or less than the above composition ratio (26 to 27%), the direction of magnetization of both layers is the same, and both layers in this state are combined into a parallel type. On the other hand, when the rare earth metal element in one magnetic layer is more than the above composition ratio (26 to 27eδ) and the rare earth metal element in the other magnetic layer is less than the above composition ratio (26 to 27%), the magnetization of both layers is The directions of the two layers are different, and both layers in this state are called antiparallel type.

The first magnetic layer 12 has a compensation composition, and the second magnetic layer 14 and the third magnetic layer 15 have an antiparallel type. moreover,
The Curie temperature can be increased by increasing the Co composition ratio.

Further, the thickness of the first magnetic layer 12 can be set to 500 to 1000, and the thicknesses of the second magnetic layer 14 and the third magnetic layer 15 can be set to t'L of 1000 to 2000, respectively, considering heat capacity.

In the embodiment, the first magnetic layer 12 is Tbts
Fett is formed to a thickness of 700 people, and the Curie temperature is TC1.
was 130°C. As the second magnetic layer 14, Tb+
, Fe1yCO2o was formed to a thickness of 2000 mm, and the Cunot temperature Tc was 200°C. The third magnetic layer 15 was formed of Tb+, FelyCO2o to a thickness of 2000 mm, and the Curie temperature Tc was 300°C.

Further, as the dielectric layer 13, Si, \, ZnS, S
in, etc., and in this example, Si+
\, was used.

In FIG. 1, the direction and magnitude of the spin of the transition metal atoms inside the alloys of the second and third magnetic layers 14 and 15 are indicated by the solid line vector ↑, and the direction and magnitude of the spin of the rare earth metal atoms are indicated by the broken line. The vector is shown in 1,000, and the direction and magnitude of magnetization of the entire alloy are shown in double solid vector lines. Double solid vector in this case? is indicated by the sum of the solid line vector ↑ and the broken line vector φ. However, inside the alloy, due to the interaction between the spin of transition metal atoms and the spin of rare earth metal atoms, the directions of the solid line vector ↑ and the dashed line vector are always opposite. Therefore, when the vector sum is zero, is it a double solid line vector? is zero, that is, the magnitude of magnetization appearing externally is zero (the alloy composition at this time is the above-mentioned compensation composition).

Furthermore, since the proportion of the rare earth metal element in the second magnetic layer 14 is smaller than the proportion in the compensation composition, the magnitude of the solid line vector 1 is larger than the magnitude of the broken line vector 7 in the opposite direction.

On the other hand, in the third magnetic layer 15, the proportion of the rare earth metal element is greater than the proportion in the compensation composition, so the magnitude of the solid line vector ↑ is smaller than the magnitude of the dashed line vector T in the opposite direction.

FIG. 2 shows the temperature characteristics of the stray magnetic fields from the second and third magnetic layers exerted on the first magnetic layer. From this drawing, the room temperature TR is Hd, #Hd, , Tc, and in the vicinity Hd, >Hd, .
It can be seen that in the temperature range of Tey - Tc, there is a relationship of Hd2<Hd.

At the time of override, only the laser beam 16 is used. This laser beam 16 is used with its power adjusted to high and low depending on the recorded information data. This low power irradiation raises the first magnetic layer 12 to its Curie temperature Tc, erases the magnetic recording information recorded in the first magnetic layer 12, and when the first magnetic layer 12 is cooled, the second magnetic layer Due to the exchange coupling force of the stray magnetic field Hd2 from 14, the stray magnetic field H
Magnetization is recorded in the direction of d. On the other hand, although high power irradiation is higher than the Curie temperature Tc2 of the second magnetic layer 14,
The magneto-optical recording medium 10 is heated to a temperature lower than the Curie temperature Tc3 of the third magnetic layer 15, and the magnetic recording information recorded in the first magnetic layer 12 is erased. Due to the exchange coupling force of the floating magnetic field Hd from the magnetic layer 15, magnetization is recorded in the direction of the floating magnetic field Hd.

This override will be explained in detail based on FIGS. 3 and 4, separately for when the power of the laser beam is high and when the power of the laser beam is low.

FIG. 3A is a schematic cross-sectional view of the medium when irradiated with a laser beam of low power 7, and FIG. 3B is a cross-sectional view of the medium when it is cooled.

In FIG. 3A, when the medium 10 is irradiated with a low-power laser beam according to the recorded information data during override, the temperature of the medium 10 becomes slightly higher than the Curie temperature Tc+ of the first magnetic layer 12. The magnetization of the first magnetic layer 12 becomes zero.

When the irradiation of the laser beam 15 is stopped and the first magnetic layer 12 is started to be cooled, the Curie temperature Tc is reached.
Since the stray magnetic field Hd2 from the magnetic layer 14 is larger than the stray magnetic field Hd from the third magnetic layer 15, the first magnetic layer 12 replaces the second magnetic layer 14 as shown by the arrow 17 in FIG. 3A. Due to the bonding force, the second magnetic layer 14 is magnetized in the same direction as the magnetization direction as shown by the arrow 18 in FIG. 3B.

Next, FIG. 4A is a schematic cross-sectional view of the medium when it is irradiated with a high-power laser beam, and FIG. 4B is a schematic cross-sectional view of the medium when it is cooled.

When the medium 10 is irradiated with a high-power laser beam as shown in FIG. Since it is heated to a lower temperature, the magnetization of the first magnetic layer 12 becomes zero. At this point, when the irradiation of the laser beam 15 is stopped and the medium 10 is started to be cooled, the Curie temperature Tc
As is clear from FIG. 2, in the temperature range near , the stray magnetic field Hd from the third magnetic layer 15 exerted on the first magnetic layer 12 is larger than the stray magnetic field Hd from the second magnetic layer 14.
As shown by the arrow 19 in FIG.
It is magnetized in the same direction as the direction of magnetization, as shown by arrow 20 in FIG. 4B. Thereafter, the first magnetic layer 12 passes through a temperature T c + in the process of reaching room temperature T6;
At this time, the temperature of the second and third magnetic layers 14 and 15 is higher than that of the first magnetic layer 12 because their heat capacity is larger than that of the first magnetic layer 12.
Temperature higher than 2. Therefore, it is not affected by the temperature Tc and the fact that the stray magnetic field Hd t from the second magnetic layer 14 exerted on the first magnetic layer 12 in the vicinity is larger than the stray magnetic field Hd s from the third magnetic layer 15 .

As described above, the power of the laser beam is adjusted to be high or low according to the recorded information data, and the direction of magnetization of the first magnetic layer 12 can be made according to the recorded information data.

At room temperature, magnetic recording in the first magnetic layer 12 is performed on the dielectric layer 1.
3, it is not affected by the stray magnetic fields Hd and Hds from the second and third magnetic layers 14 and 15.

(G) Effects of the Invention The present invention provides a substrate with a first magnetic layer having a magneto-optic effect, a dielectric layer, and a second and third magnetic layer having perpendicular magnetic anisotropy and having an antiparallel type. and are sequentially laminated, and the first
5 The third magnetic layer has its Curie temperature Tc+, Tc7
, Tc, then Tc+<Tc+<Tc+,
Moreover, when the magnitude of the stray magnetic field of the second magnetic layer and the third magnetic layer with respect to the first magnetic layer is Hd,, Hd, at room temperature, Hd+4=;Hd,, Tc, and in the vicinity, Hdt > Hd.
h, Tc.

Since it is characterized by the relationship of Id<Hdl in the temperature range from Tc to Tc, the magnitude of the stray magnetic field can be adjusted by switching the power of the laser beam to high or low in accordance with the recorded information data during override. By utilizing this change, magnetic recording can be performed in accordance with the recorded information data, and it is possible to provide a magneto-optical recording medium that does not require conventional initialization magnets and bias magnets.

[Brief explanation of drawings]

Figures 1-5 and 4-j show one implementation of the present invention fM+-1
FIG. 1 (Schematic sectional view of a magneto-optical recording medium according to the present invention,
Fig. 2 is an explanatory diagram of the relationship between the magnitude of the stray magnetic field from the second and third magnetic layers and temperature, Fig. 3A is a schematic cross-sectional view of the medium during irradiation with a low-power laser beam, and Fig. 3A is a schematic cross-sectional view of the medium when it is cooled. FIG. 4A is a schematic cross-sectional view of the medium when it is irradiated with a high-power laser beam, and FIG. 4B is a schematic cross-sectional view of the medium when it is cooled. Figure 5 not shown: Figure 7 shows a conventional example, Figure 5 is a perspective view of a conventional magneto-optical recording medium, Figure 6 is a schematic sectional view of the medium, Figure 7 shows a conventional example.
The figure is an explanatory diagram of the relationship between the temperature of each magnetic layer of the medium and the strength of the magnetic field. 10-------5 magneto-optical recording medium, l 1-----
---1 substrate, 12--11-11 first magnetic layer, 13-
---------1st dielectric layer, 14------5 2nd magnetic layer, 15------5 3rd magnetic layer, 16~------
--Laser light.

Claims (1)

[Claims] (1) a first magnetic layer having a magneto-optic effect on the substrate;
A dielectric layer, a second magnetic layer and a third magnetic layer of an anti-parallel type having perpendicular magnetic anisotropy are sequentially laminated, and the first to third magnetic layers have their Curie temperatures Tc_1, Tc_
2. When Tc_3, Tc_1<Tc_2<Tc_
3, and when the magnitudes of the floating magnetic fields of the second and third magnetic layers with respect to the first magnetic layer are Hd_2 and Hd_3, at room temperature Hd_2≒Hd_3 Near Tc_1, Hd
A magneto-optical recording medium characterized by a relationship of Hd_2<Hd_3 in the temperature range of _2>Hd_3 and Tc_2 to Tc_3.