JPH10106058A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium which is easily produced and in which the recording characteristic of optical modulation direct overwriting is improved. SOLUTION: The magneto-optical recording medium 1 is constituted by laminating at least magnetic thin films 4 to 6 in three layers. The magnetic thin films 4, 6 are composed of an amorphous films consisting of rare earth-3d transition metals having perpendicular magnetic anisotropy or intrasurface magnetic anisotropy at room temp. and are magnetically bonded via a magnetic thin film 5. The magnetic thin film 5 is composed of rare earth metals-dominant film which is small in exchange energy with rare earth-3d transition metals and has magnetic anisotropy in the intrasurface direction and controlls the magnetical bonding state of the magnetic thin films 4, 6.

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 for recording and reproducing information by irradiating light such as laser light.

[0002]

2. Description of the Related Art In a method of recording information on a recording medium in which information marks (magnetic domains) are read out by magneto-optical interaction, a recording medium having a magnetic thin film of a perpendicular magnetization film has its magnetization direction directed to the film surface. A so-called initialization is performed in advance so as to be aligned in one perpendicular direction, and a magnetic domain having perpendicular magnetization in the opposite direction to this magnetization direction is formed by local heating such as laser light irradiation, thereby forming a binary information mark. Records and saves information. In such a recording method, a process of erasing (or initializing) the recorded information, that is, a time for initialization is required prior to rewriting of the information, and recording of the information at a high transfer rate cannot be realized.

To cope with this problem, various recording methods using overwriting, that is, a so-called overwrite method, in which the time for such an independent initialization process is not required, have been proposed and realized. Among these various overwrite recording methods, a light modulation direct overwrite technique is promising as a fusion technique with a magnetic super-resolution technique for higher density in the future. This can be easily rewritten, that is, overwritten, simply by switching and controlling the heating temperature of the medium by laser light or the like. Japanese Patent Application Laid-Open No. 62-17594 discloses a basic technology of a recording medium for realizing the light modulation direct overwrite.
No. 8 discloses a technique disclosed in Japanese Patent Laid-Open Publication No. 8 (1999) -86.

That is, the magneto-optical recording method disclosed in this application uses a recording medium having a laminated structure of first and second rare earth-transition metal magnetic thin films, and applies a required first external magnetic field. first and Atsushi Nobori heating at a temperature inversion does not occur in the sublattice magnetization of the second magnetic thin film, and the Curie temperature T _c above the temperature T ₁ of the first magnetic thin film, and at a temperature above T ₁ The second temperature rising state of heating to a _second temperature T ₂ sufficient to reverse the sublattice magnetization of the second magnetic thin film is modulated in accordance with information “0” and “1” to be recorded, During the cooling process, the direction of the sublattice magnetization of the first magnetic thin film is aligned with the direction of the sublattice magnetization of the second magnetic thin film by the exchange coupling force due to the exchange interaction between the first and second magnetic thin films, and "
Recording marks (magnetic domains) of 0 "and" 1 "are formed on the first magnetic thin film, and the second external magnetic field is used to form the second recording mark at room temperature.
Only the sub-lattice magnetization of the magnetic thin film is inverted in one direction to enable direct overwriting. The magneto-optical recording medium used for this is made to realize the above-mentioned state. Provided by a perpendicular magnetic two-layered film. FIG. 10 is a diagram for explaining the magnetization state of the magneto-optical recording medium from room temperature to the recording temperature.

In this magneto-optical recording medium, exchange energy acts on the interface between the laminated first magnetic thin film and second magnetic thin film.
In state B (FIG. 10) of K), an interface domain wall is generated. Interface wall energy sigma _w in this _{case, H wi = σ w / 2M} si h i ·············· (1) where, H _wi: a magnetic layer i-layer adjacent effective bias field M _si receive: saturation magnetization of the i-th magnetic layer h _i: represented a thickness of i-th magnetic layer, sigma _w = about _{2 {(a 1 K 1)} 1/2 + (a 2 K ₂ ) ^1/2 ｝ (2) where A ₁ : exchange stiffness constant of the first magnetic thin film A ₂ : exchange stiffness constant of the second magnetic thin film K ₁ : effective difference of the first magnetic thin film It is considered that the anisotropic constant K _{2 is} an effective anisotropic constant of the second magnetic thin film.

The conditions for overwriting are as follows:
In order to prevent the transition from the state B to the state A at room temperature, the following conditions must be satisfied. H _c1 > H _w1 = σ _w / 2M _s1 h ₁ (3) where H _c1 : coercive force of the first magnetic thin film H _w1 : the first magnetic thin film is adjacent Effective magnetic field received from the applied magnetic layer M _s1 : saturation magnetization of the first magnetic thin film h ₁ : film thickness of the first magnetic thin film

In order to prevent the transition from the state B to the state E at room temperature, the following conditions must be satisfied. H _c2 > H _w2 = σ _w / 2M _s2 h ₂ (4) where H _c2 : coercive force of the second magnetic thin film H _w2 : the second magnetic thin film is adjacent Effective magnetic field M _s2 : Saturation magnetization of the second magnetic thin film h ₂ : Thickness of the second magnetic thin film

Further, in order to prevent the first magnetic thin film from being inverted by the external initialization auxiliary magnetic field H _ini in the state E, the following condition must be satisfied. _Hc1 ± _Hw1 > _Hini (5) Here, “±” on the left side indicates that the first magnetic thin film is a rare-earth dominant film and the second When the magnetic thin film is a transition metal dominant thin film (or vice versa) (that is, anti-parallel coupling), it becomes “+”, and the first and second magnetic thin films are both transition metal (or both). When the film is a predominant film (rare earth metal) (that is, in the case of parallel coupling), "-" is displayed.

On the other hand, in order to enable the transition from the state E to the state B, the following conditions must be satisfied. H _c2 + H _w2 <H _ini (6)

Further, when the temperature rise state is near the Curie temperature _Tc1 of the first magnetic thin film, the transition from the state C to the state A, that is, the direction of the magnetization of the first magnetic thin film is the same as the direction of the magnetization of the second magnetic thin film. In order to be aligned, it is necessary to satisfy the following conditions. H _w1 > H _c1 + H _ex (7) where H _{ex is the} recording external magnetic field

Further, in order to prevent the transition from the state C to the state E, it is necessary to satisfy the following condition. H _c2 −H _w2 > H _ex・ ・ ・ ・ ・ ・ ・ ・ ・ (8)

[0012]

As is apparent from the above, at room temperature, the interface domain wall energy σ _w is desirably small in order to satisfy the above equations (3) and (4). In the vicinity of the temperature at which the direction of magnetization of the second magnetic thin film is aligned with the direction of magnetization of the second magnetic thin film, the interface domain wall energy σ _w is set to the value (7) in order to strongly exert the exchange interaction.
It is necessary to maintain a state where the magnitude, that is, the magnitude of σ _w at room temperature, does not change, or even if it does change, the degree of decrease is small, while satisfying the expression (8). . However, it has been extremely difficult to achieve a state satisfying all of these factors only by controlling the coercive force, saturation magnetization, and film thickness of the first and second magnetic thin films.

According to the present invention, there is provided a third magnetic thin film which is a rare earth metal dominant film for controlling magnetic characteristics generated by an exchange coupling force due to an exchange interaction between the first and second magnetic thin films. Provided in the middle of the second magnetic thin film, and
By controlling the composition of the magnetic film or adding another metal element, not only is it easy to prepare a medium with excellent characteristics, but also the recording characteristics are improved, and furthermore, an effective control layer in the exchange coupling multilayer film in general. It is an object of the present invention to provide a magneto-optical recording medium having:

[0014]

In order to solve the above-mentioned problems, the present invention provides a magneto-optical recording medium having the following constitutions (1) to (3).

(1) As shown in FIG.
A magneto-optical recording medium 1 in which first, second, and third magnetic thin films 4 to 6 are sequentially stacked, wherein the first and third magnetic thin films 4 and 6 have a perpendicular magnetic anisotropy or room temperature. The second magnetic thin film 5 is composed of an amorphous thin film made of a rare earth metal-3d transition metal having in-plane magnetic anisotropy, and is magnetically coupled via the second magnetic thin film 5. The rare earth metal which has a small exchange energy with the rare earth metal-3d transition metal and has magnetic anisotropy in the in-plane direction (R
An magneto-optical recording medium 1 comprising an E-rich film.

(2) The second magnetic thin film 5 is an amorphous thin film having magnetic anisotropy in the in-plane direction.
The magneto-optical recording medium according to (1) above, wherein r (erpium) or Ho (holmium) is a film using Fe (iron) or FeCo (iron-cobalt alloy) as a 3d transition metal.

(3) The second magnetic thin film 5 is an amorphous thin film having magnetic anisotropy in an in-plane direction,
(Holmium / iron alloy), HoFeCo (holmium / iron alloy)
Iron / cobalt alloy), ErFe (erpium / iron alloy)
Or ErFeCo (erpium-iron-cobalt alloy) as a base and Bi as another metal
(1) The magneto-optical recording medium according to the above (1), wherein the film is a film to which any one of (bismuth), Sn (tin) and Lu (lutetium) is added.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a magneto-optical recording medium of the present invention will be described in the order of [Embodiment 1] and [Embodiment 2] with reference to FIGS.

Example 1 Magneto-optical recording medium 1 of the present invention
As shown in FIG. 1, a first film is formed on a light transmitting substrate 2 such as a glass plate or a polycarbonate (the lower surface in FIG. 1) via a transparent dielectric film 3 serving as a protective film or a multiple interference film. To form three-layer magnetic films (first, second, and third magnetic thin films) 4, 5, and 6 in which a third magnetic thin film is sequentially laminated in vacuum, for example, by continuous sputtering or the like. A protective film 7 made of a non-magnetic metal film or a dielectric film is formed on a magnetic thin film 6 (the lower surface in the figure). Irradiation with laser light or the like is performed from the light transmitting substrate 2 side. The first and third magnetic thin films 4 and 6 are made of rare earth-3d having perpendicular magnetic anisotropy or in-plane magnetic anisotropy at room temperature.
It is composed of an amorphous thin film made of a transition metal.
The second magnetic thin film 5 is composed of a rare-earth-metal-dominant (RE-rich) film having a small exchange energy with the rare-earth-3d transition metal and having magnetic anisotropy in the in-plane direction.

The first magnetic thin film 4 is made of, for example, TbFe (terbium iron alloy) or TbFeCo (terbium iron).
(Cobalt alloy). The third magnetic thin film 6 is made of, for example, DyFeCo (dysprosium-iron-cobalt alloy).

The second magnetic thin film 5 as an intermediate layer is made of a rare earth metal predominant, for example, HoFe (holmium-iron alloy) or HoFeCo (holmium-iron-cobalt alloy), E
It is composed of a thin film of rFe (erpium / iron alloy) or ErFeCo (erpium / iron / cobalt alloy). Specifically, in Er _x (Fe _{1 -y} Co _y ) _{1 -x} , 0.26 ≦ x ≦ 0.50, 0 ≦ y ≦ 0.3 (x, y
Is the atomic content ratio). HoFe or HoFeCo, ErFe, E
Bi based on one of rFeCo and other metal
It is constituted by adding an element such as (bismuth), Sn (tin) or Lu (lutetium) to reduce the exchange energy between the rare earth metal and the 3d transition metal.

The temperature characteristics of the interface domain wall energy, which is important in the present invention, and its effective control method will be described below.

FIG. 2 shows the temperature characteristics of the magnetization and the temperature characteristics of the effective anisotropy (Ku-2πMs ² ) of each layer (first magnetic thin film 4 to third magnetic thin film 6) constituting the magneto-optical recording medium 1. Are measured and the parameters of the molecular field theory are determined to calculate the temperature dependence of the interface domain wall energy. -Rich) is a graph comparing with the case using a membrane.

In FIG. 2, "Interface wall"
“energy” (unit: erg / cm ² ) is the interface domain wall energy, “Temperature” (unit: K)
Indicates an absolute temperature.

In FIG. 2, “σ _B of 3” indicated by a thin line
“rd Layer (DyfeCo)” is the temperature dependence of the Bloch domain wall energy of the third magnetic thin film 6 using a DyFeCo film, and “σ _B of 1st Layer” indicated by a thin line.
“r (TbFe)” is the temperature dependence of the Bloch domain wall energy of the first magnetic thin film 4 using a TbFe film, and “RE-rich 2nd Layer” shown by a thick line is a rare earth metal dominant (RE-rich) film. Temperature dependence of interface domain wall energy when used as magnetic thin film 5, and
“TM-rich 2nd Layer” indicated by a thick line indicates that the transition metal dominant (TM-rich) film is the second magnetic thin film 5.
3 shows the temperature dependence of the interface domain wall energy when used as.

In FIG. 2, "RE-rich" at room temperature was used.
2nd Layer "," TM-rich 2nd
The interfacial domain wall energy of “Layer” is a value in consideration of the above equations (5) and (6), and is about 1.2 erg / cm ² in both cases. It can be seen that there is a difference.

FIG. 3 shows the temperature dependence of the magnetization of the second magnetic layer 5 constituting the magneto-optical recording medium 1 by showing that the rare-earth gold dominance (RE-
7 is a graph comparing the case of using a transition metal dominant (TM-rich) film with the case of using a transition metal dominant (TM-rich) film.

In FIG. 3, "Magnetization"
(Unit: emu / cm ³ ) is magnetization, “TM-rich”
Is the temperature dependence of the magnetization of the transition metal dominant film, "RE-ric
"h" indicates the temperature dependence of the magnetization of the rare earth metal dominant film.

FIG. 4 shows the temperature dependence of the effective anisotropy (Ku-2πMs ² ) of the second magnetic layer 5 constituting the magneto-optical recording medium 1 by comparing the rare-earth metal dominant (RE-rich) film with the transition metal. It is a graph compared with the dominant (TM-rich) film.

In FIG. 4, “Ku” (unit: 10 ⁵ erg /
cm ³ ) is the true anisotropy, “Ku−2πMs ² ” (unit:
10 ⁵ erg / cm ³ ) is the effective anisotropy, “Ku (R
E-rich) is rare earth metal dominant (RE-rich)
Temperature dependence of the true anisotropy of "Ku (TM-ric
h) "is the temperature dependence of the true anisotropy of the transition metal dominant (TM-rich) film," Ku-2πMs ² (RE-ric)
h) is the temperature dependence of the effective anisotropy of the rare-earth metal predominant (RE-rich) film, and “Ku−2πMs ² (T
“M-rich)” indicates the temperature dependence of the effective anisotropy of the transition metal dominant (TM-rich) film.

FIG. 2 shows "TM-rich 2n".
The interface domain wall energy of “d Layer” is “RE-ri
The graph shows that the temperature sharply decreases with an increase in temperature as compared with the interface domain wall energy of “ch 2nd Layer”.

FIG. 3 shows that the temperature change of the magnetization of “RE-rich” decreases more rapidly than the temperature change of the magnetization of “TM-rich” (“TM-rich”).
ch ”is convex upward).

FIG. 4 shows "Ku-2πMs".
It is shown that the temperature change of the effective anisotropy of “ ² (RE-rich)” increases more rapidly than the temperature change of the effective anisotropy of “Ku−2πMs ² (TM-rich)” ( "Ku-2πMs ² (TM-rich)" is convex downward).

On the other hand, the magnetic transfer from the first magnetic thin film 4 to the second magnetic thin film 5 is based on the above equations (7) and (8).
It is desirable that the degree of reduction of the interface domain wall energy with a rise in temperature is smaller. Preferable for this condition is “RE-rich 2nd” shown in FIG.
Layer "characteristics. Therefore, the magnetic transfer when the rare earth metal dominant (RE-rich) film is used as the second magnetic thin film 5 is the magnetic transfer when the transition metal dominant (TM-rich) film is used as the second magnetic thin film 5. It can be said that it can be performed better.

On the other hand, the domain wall energy σ _w is
As shown in the equation (2), σ _w = about 2 {(A ₁ K ₁ ) ^1/2 + (A ₂ K ₂ ) ^1/2 } (2) where A _{1 is} the first magnetic thin film. Exchange stiffness constant A ₂ : Exchange stiffness constant of _second magnetic thin film K ₁ : Effective anisotropic constant of first magnetic thin film K ₂ : Effective anisotropic constant of second magnetic thin film Therefore, it is considered that the interface domain wall shifts to the side where the value of the AK product is smaller. By lowering the perpendicular magnetic anisotropy energy of the second magnetic layer 5 which is the intermediate layer, most of the interface domain wall exists in the second magnetic layer 5, and the recorded magnetic domain exists stably. Will be. Accordingly, desirable to lower the second perpendicular anisotropy energy of the magnetic layer 5 in the entire temperature range to a temperature (T ₂ vicinity) performed the recording from room temperature. To this end, the temperature is carried out with recording from room It can be said that the second magnetic layer 5 preferably has in-plane magnetic anisotropy in the entire temperature range up to.

As described above, the first and third thin films having perpendicular (or in-plane at room temperature) magnetic anisotropy made of a rare earth-3d transition metal are formed with the second magnetic thin film interposed therebetween. In the recorded recording thin film medium, the first and third
Are sequentially magnetically coupled and laminated via a second magnetic layer, and a second magnetic thin film for controlling the coupling state is rare earth metal dominant (RE-ric).
h) It can be said that a film having a small exchange energy between the rare earth element and the 3d transition metal and having magnetic anisotropy in the in-plane direction is effective for improving the recording characteristics.

[Embodiment 2] As in Embodiment 1 of the present invention described above, the temperature characteristic of the interface domain wall energy is
This greatly depends on the temperature characteristics of the magnetization of the magnetic layer 5) and the temperature characteristics of the effective anisotropy. Therefore, by controlling the magnetization and the effective anisotropy, the temperature characteristics of the interface domain wall energy can be further improved.

Controlling the exchange energy acting between the rare earth metal (Re) and the 3d transition metal in the molecular field theory is effective in improving the temperature characteristics. When an element such as Bi or Sn is added to the intermediate layer, the compensation temperature decreases, and the exchange energy acting between the rare earth metal and the 3d transition metal can be reduced.

FIG. 5 is a graph comparing the temperature dependence of the magnetization in the second magnetic layer 5 with two types of rare earth metal dominant films in which the exchange energy acting between the rare earth metal and the 3d transition metal is changed.

In FIG. 5, “J _ReFe = −1.7 × 10 ^−15”
“erg” is the temperature dependence of magnetization when the exchange energy between Re and Fe of the second magnetic layer 5 is −1.7 × 10 ⁻¹⁵ erg, and “J _ReFe = −1.2 × 10 ⁻¹⁵ erg. Is the second
The exchange energy between Re and Fe of the magnetic layer 5 is -1.2.
The graph shows the temperature dependence of the magnetization at the time of × 10 ⁻¹⁵ erg.

FIG. 6 is a graph comparing the temperature dependency of the anisotropy in the second magnetic layer 5 with two types of rare earth metal dominant films in which the exchange energy acting between the rare earth metal and the 3d transition metal is changed. is there.

In FIG. 6, “Ku (J _ReFe = −1.7 × 1)
“0 ⁻¹⁵ erg)” is the temperature dependence of the true anisotropy when the exchange energy between Re—Fe of the second magnetic thin film 5 is −1.7 × 10 ⁻¹⁵ erg, and “Ku (J _ReFe) = -1.2
× 10 ⁻¹⁵ erg) ”is the temperature dependence of the true anisotropy when the exchange energy between Re and Fe of the second magnetic thin film 5 is −1.2 × 10 ⁻¹⁵ erg, and“ Ku−2πMs ² (J
_ReFe = −1.2 × 10 ⁻¹⁵ erg) ”represents the second magnetic thin film 5
Has an exchange energy between Re and Fe of -1.2 × 10 ^-15
erg, the temperature dependence of the effective anisotropy, and “Ku−2πMs ² (J _ReFe = −1.7 × 10
^-15 erg) indicates the temperature dependence of the effective anisotropy when the exchange energy between Re and Fe of the second magnetic thin film 5 is -1.7 × 10 ^-15 erg.

FIGS. 5 and 6 show that the exchange energy between the rare earth metal and the 3d transition metal was −1.7 × 10 ⁻¹⁵ erg −
FIG. 4 shows the temperature characteristics of magnetization and anisotropy when the temperature is reduced to 1.2 × 10 ⁻¹⁵ erg.
As can be seen from comparison with, the magnetization and the effective anisotropy fluctuate greatly. Exchange energy J between Re and Fe
_{When ReFe} is lowered, the magnetization decreases almost linearly with the temperature rise, and as a result, the effective anisotropy draws an upwardly convex curve and sharply increases.

FIG. 7 shows the temperature dependence of the interface domain wall energy in the case where a rare earth metal dominant (RE-rich) film is used for the second magnetic layer 5 used in the comparison of FIG. Rare earth metal dominant (RE-rich) with reduced exchange energy acting between rare earth metal and 3d transition metal (Re-Fe)
It is a graph compared with the case where a film was used.

In FIG. 7, "2nd Layer (J _ReFe
= −1.7 × 10 ⁻¹⁵ erg) ”means rare earth metal dominant (RE−
rich) The temperature dependence of the interface domain wall energy when the exchange energy between Re and Fe of the second magnetic thin film 5 using the film is -1.7 × 10 ^-15 erg, "2nd La
yer (J _ReFe = −1.2 × 10 ⁻¹⁵ erg) ”indicates the R of the second magnetic thin film 5 using a rare earth-dominant (RE-rich) film.
The exchange energy between e-Fe is -1.2 × 10 ^-15 er
The temperature dependence of the interface domain wall energy in the case of g is shown.

As is clear from FIG. 7, the rare earth metal and 3
It can be seen that in the medium using the intermediate layer (second magnetic thin film 5) having a lower exchange energy acting between the d transition metals, the degree of decrease in the interface domain wall energy with a rise in temperature becomes more moderate. As a result, the transferability of the magnetization is further improved.

From the above equation (7), the difference in the transferability of magnetization is expressed by (H _c1 −H _w1 H _c1 : coercive force of the first magnetic thin film,
H _w1: Although the first magnetic thin film can be said to be determined by the effective bias magnetic field) received from the magnetic layer adjacent, (H _c1
When −H _w1 ) is negative and the absolute value is large, the transferability is better.

[0048] Although it can be said that the difference between the transfer of the magnetization can be judged by the above-described (7) by equation _{(H c1 -H w1), (} H c1 -
_Hw1 ) is negative and the absolute value is large, the better the transferability.

The exchange energy between the (H _c1 -H _w1 ), the rare earth metal and the 3d transition metal of the two media used in the comparison of FIG.
ch) of the medium using the film for the second magnetic layer 5 (H _c1 −
FIG. 8 is a graph comparing the temperature change of H _w1 ).

In FIG. 8, “H _c1 −H _w1 ” (unit: kOe)
Is the value obtained by subtracting the effective bias magnetic field H _w1 that the first magnetic thin film receives from the adjacent magnetic layer from the coercive force H _c1 of the first magnetic thin film, “TM-rich 2nd Layer (J
_ReFe = −1.7 × 10 ⁻¹⁵ erg) ”is the transition metal dominant (TM
-Rich) In the medium using the film as the second magnetic thin film 5, the exchange energy between Re and Fe is -1.7 × 10 ^-15.
erg (H _c1 −H _w1 ), “RE-rich
2nd Layer (J _ReFe = −1.7 × 10 ⁻¹⁵ er
g) "means (H _c1 ) when the exchange energy between Re and Fe is −1.7 × 10 ⁻¹⁵ erg in a medium using a rare earth metal predominant (RE-rich) film as the second magnetic thin film 5.
-H _w1 ) and "RE-rich 2nd Layer
er (J _ReFe = −1.2 × 10 ⁻¹⁵ erg) ”means that the exchange energy between Re—Fe in a medium using a rare earth metal predominant (RE-rich) film as the second magnetic thin film 5 is −1.2.
(H _c1 −H _w1 ) in the case of × 10 ⁻¹⁵ erg.

As is clear from FIG. 8, when the transition metal dominant (TM-rich) film is used for the second magnetic layer 5 as the intermediate layer, the rare earth metal dominant (RE-rich) film is used. In addition, rare earth metal dominant (RE-ric) with reduced exchange energy between rare earth metal and 3d transition metal
h), the maximum value of the negative absolute value of (H _c1 −H _w1 ) increases in the order of the medium using the intermediate layer, and it can be said that the transferability of magnetization is improved in this order.

As described above, these characteristics are improved by changing the temperature characteristics of the magnetization of the intermediate layer (the second magnetic layer 5). As a method for effectively changing the characteristics, E
It is conceivable to use a rare earth element such as r or Ho for the intermediate layer.

FIG. 9 shows five different rare earth elements (Gd
4 is a graph comparing the temperature characteristics of magnetization of alloy thin films of (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erpium)) and Fe (iron).

In order to improve the characteristics as the control layer, that is, to improve the temperature characteristics of the interface domain wall energy, it can be said that it is desirable that the magnetization decreases more rapidly as the temperature rises. It can be said that better characteristics can be improved by using HoFe. Also, for these alloy thin films, Bi, Sn,
Alternatively, it can be said that by adding an element such as Lu, the exchange energy acting between the rare earth metal and the 3d transition metal can be reduced, whereby the characteristics can be further improved.

[0055]

As described above, according to the present invention, the second magnetic thin film for controlling the interface domain wall energy is provided between the first and third magnetic thin films, and the second magnetic thin film is heated from room temperature to high temperature. A rare earth metal predominant composition having in-plane magnetic anisotropy in the region, and HoFe or HoFeCo, ErFe, ErFeC
Based on o, add metals such as Bi and Sn,
By a film having a certain thickness can be obtained suppressing the interface wall energy, keep increasing the magnetic wall energy at the temperature T ₁ of the vicinity effect near room temperature. Thereby, the domain wall is stabilized at room temperature, and the temperature T ₁
In the vicinity, it is possible to enhance the stability of the transfer of the recording magnetic domain. Further, the present invention is not limited to providing a medium capable of realizing the improvement of the characteristics of the information overwriting direct overwrite, and also relates to a magnetic super-resolution magnetic multilayer film technology for high density in the future. The present invention can be used for improving and controlling the exchange coupling control magnetic layer, and can provide a technique essential for diversifying and improving the magnetic recording / reproducing function by the exchange coupling multilayer film.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a magneto-optical recording medium of the present invention.

FIG. 2 is a graph showing the relationship between a temperature characteristic of magnetization and a temperature characteristic of effective anisotropy of a first magnetic thin film to a third magnetic thin film constituting a magneto-optical recording medium, and determining and calculating parameters of molecular field theory. 7 is a graph comparing the temperature dependence of the interface domain wall energy between a case where a rare earth metal dominant film is used as a second magnetic layer and a case where a transition metal dominant film is used as a second magnetic layer.

FIG. 3 is a graph comparing the temperature dependence of magnetization in a second magnetic layer constituting a magneto-optical recording medium between a rare earth metal dominant film and a transition metal dominant film.

FIG. 4 is a graph comparing the temperature dependence of the effective anisotropy of a second magnetic layer constituting a magneto-optical recording medium between a rare-earth metal dominant film and a transition metal dominant film.

FIG. 5 is a graph comparing the temperature dependence of the magnetization in the second magnetic layer between two types of rare earth metal dominant films in which the exchange energy acting between the rare earth metal and the 3d transition metal is changed.

FIG. 6 is a graph comparing the temperature dependence of the anisotropy in the second magnetic layer 5 between two types of rare earth metal dominant films in which the exchange energy acting between the rare earth metal and the 3d transition metal is changed.

FIG. 7 shows the temperature dependence of the interface domain wall energy when the rare earth metal dominant film is used for the second magnetic layer 5 used in the comparison of FIG. 2 and when the rare earth metal and the 3d transition metal are used for the second magnetic layer 5; 7 is a graph comparing with a case where a rare earth metal dominant film whose exchange energy is reduced is used.

FIG. 8 shows (H _c1 −H) of the two types of media used in the comparison of FIG.
₄ is a graph comparing the temperature change of (H _c1 −H _w1 ) of a medium using a rare earth metal dominant film having a lower exchange energy acting between the rare earth metal and the 3d transition metal for the second magnetic layer.

FIG. 9 is a graph comparing the temperature characteristics of magnetization of alloy thin films of five kinds of rare earth elements and 3d transition metals.

FIG. 10 is a diagram for explaining a magnetization state (in the case of parallel coupling) of a magneto-optical recording medium from room temperature to a recording temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical recording medium 2 Transparent substrate 3 Dielectric film 4-6 First magnetic thin film-Third magnetic thin film 7 Protective film

Claims (3)

[Claims] 1. A magneto-optical recording medium in which at least first, second, and third magnetic thin films are sequentially laminated, wherein the first and third magnetic thin films have perpendicular magnetic anisotropy or room temperature. The second magnetic thin film is composed of an amorphous thin film made of a rare earth metal-3d transition metal having in-plane magnetic anisotropy, and is magnetically coupled via the second magnetic thin film; A magneto-optical recording medium comprising a rare earth metal dominant (RE-rich) film having a small exchange energy with a metal-3d transition metal and having magnetic anisotropy in an in-plane direction. 2. The second magnetic thin film is an amorphous thin film having in-plane magnetic anisotropy, wherein Er (erpium) or Ho (holmium) is used as a rare earth element and Fe is used as a 3d transition metal.
2. The magneto-optical recording medium according to claim 1, wherein the film is a film using (iron) or FeCo (iron-cobalt alloy). 3. The second magnetic thin film is an amorphous thin film having magnetic anisotropy in an in-plane direction. Alloy) or ErFe
Based on any one of Co (erpium, iron, cobalt alloy), and Bi (bismuth) as another metal,
2. The magneto-optical recording medium according to claim 1, wherein the film is a film to which either Sn (tin) or Lu (lutetium) is added.