JPH10106057A - 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 or optical modulation direct overwriting is improved. SOLUTION: The magneto-optical recording medium 1 is constituted by successively laminating at least magnetic thin films 4 to 6. The magnetic thin films 4, 6 are composed of an amorphous films consisting of rare earth-3d transition metals having perpendicular magnetic anisotropy and are magnetically bonded via a magnetic thin film 5. The magnetic tin film 5 is composed or rare earth metals-dominant (RE-rich) film which is small in exchange energy with rare earth-3d transition metals by adding Bi (bismuth) and Sn(tin) and has magnetic anisotropy in the intrasurface direction at a temp. of at least 100 deg.C or above and controlls the magnetical bonding state of the magnetic tin 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.

In other words, the magneto-optical recording method disclosed in this proposal 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. 15 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, an exchange energy acts on the interface between the laminated first magnetic thin film and second magnetic thin film.
In 5), 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. H _c1 ± H _w1 > H _ini (5) Here, ± on the left side indicates that the first magnetic thin film is a rare-earth dominant film and the second magnetic thin film is If the thin film is a transition metal dominant thin film (or vice versa) (ie, anti-parallel coupling), it becomes “+”, and the first and second magnetic thin films are both transition metal (or both rare earth metal). ) When the film is a dominant film (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 magnetization direction of the first magnetic thin film is changed to the magnetization direction of the second magnetic thin film. In order to be aligned, the following conditions must be satisfied. 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 having excellent characteristics, but also the recording characteristics are improved, and furthermore, the effective control of the exchange-coupled multilayer film in general is effective. It is an object to provide a magneto-optical recording medium provided with a layer.

[0014]

To solve the above-mentioned problems, the present invention provides a magneto-optical recording medium having the following constitutions (1) and (2).

(1) As shown in FIG.
1. 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, 6 are rare earth elements having perpendicular magnetic anisotropy. -3d transition metal, and is magnetically coupled through the second magnetic thin film 5, the second magnetic thin film 5 has an exchange energy with the rare earth-3d transition metal. 1. A magneto-optical recording medium 1 comprising a rare-earth-metal-dominant (RE-rich) film having a small thickness and having magnetic anisotropy in the in-plane direction at 100 ° C. or higher.

(2) The second magnetic thin film 5 is an amorphous thin film having in-plane or vertical magnetic anisotropy at room temperature, wherein Gd (gadolinium) is used as a rare earth element and Fe (iron) or 3D transition metal is used as a 3d transition metal. FeCo (iron-cobalt alloy) is used, and Bi (bismuth), S
The magneto-optical recording medium according to the above (1), wherein the exchange energy acting between the rare earth and the 3d transition metal is reduced by adding n (tin).

[0017]

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.

Embodiment 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 rare earth-
It is an amorphous thin film made of a 3d transition metal and has perpendicular magnetic anisotropy. The second magnetic thin film 5 is a rare earth-3d
Low exchange energy with transition metal and at least 1
It is composed of a rare earth metal predominant (RE-rich) film having magnetic anisotropy in the in-plane direction at a temperature of 00 ° C. or more.

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, GdFe (gadolinium-iron alloy) or GdFeCo (gadolinium-iron-cobalt alloy).
It consists of a thin film. Specifically, Gd _x (Fe
_1-y Co _y ) In _1-x , 0.32 ≦ x ≦ 0.50, 0 ≦ y ≦ 0.3 (x, y
Is the atomic content ratio), and is formed by reducing the exchange energy between the rare earth and the 3d transition metal by adding other metal elements such as Bi (bismuth) and Sn (tin) based on GdFeCo.

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 (the first magnetic thin film 4 to the third magnetic thin film 6) constituting the magneto-optical recording medium 1. Are measured to determine the parameters of the molecular field theory, and the calculated temperature dependence of the interface domain wall energy is compared with the case where a rare earth metal dominant (RE-rich) film is used for the second magnetic layer 5 and the case where the transition metal dominates (TM). -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 the rare-earth gold dominance (RE-
rich) GdFe and transition metal dominant (TM-ric)
h) A graph comparing GdFe of the film.

In FIG. 3, "Magnetization"
(Unit: emu / cm ³ ) is magnetization, “GdFe (TM−
“rich” indicates the temperature dependence of the magnetization of GdFe of the transition metal dominant film, and “GdFe (RE-rich)” indicates the temperature dependence of the magnetization of GdFe 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 using the GdF of the rare-earth metal dominant (RE-rich) film.
7 is a graph comparing e with GdFe of a transition metal 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 of
GdFe (RE-rich) ”is a rare earth metal dominant (R
E-rich) The temperature dependence of the true anisotropy of GdFe, "Ku of GdFe (TM-rich)" is the temperature dependence of the true anisotropy of GdFe of the transition metal dominant (TM-rich) film. , "Ku-2πMs ² of GdFe
(RE-rich) ”is rare earth metal dominant (RE-ric)
h) Temperature dependence of the effective anisotropy of GdFe of the film, and “Ku-2πMs ² of GdFe (TM-ric
h) "is the transition metal dominant (TM-rich) film GdFe
Respectively show the temperature dependence of the effective anisotropy of.

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 “GdFe (RE-ri)
ch)) changes in temperature of the magnetization of “GdFe (TM-ric)
h) ”shows that the magnetization decreases more rapidly than the temperature change (“ GdFe (TM-rich) ”protrudes upward).

Further, FIG. 4 shows "Ku-2πMs ² o
The temperature change of the effective anisotropy of “f GdFe (RE-rich)” is “Ku−2πMs ² of GdFe (TM-r
ich) ”, the effective anisotropy increases more rapidly than the temperature change (“ Ku−2πMs ² of G ”).
dFe (TM-rich) "protrudes 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 of GdFe is a transition metal dominant (TM-r).
ich) It can be said that the transfer can be performed better than the magnetic transfer when the GdFe film is used as the second magnetic thin film 5.

FIG. 5 shows the magneto-optical recording medium 1 shown in FIG. 2 and a first magnetic thin film 4 using a TbFe film and a DyFe film.
6 is a graph showing a temperature change of a coercive force Hc of a third magnetic thin film 6 using a Co film.

In FIG. 5, "Coercity Hc"
(Unit: kOe) is the coercive force and “1st Layer (T
bFe) is the coercive force of the first magnetic thin film 4 using a TbFe film, and “3rd Layer (DyfeCo)” is Dy
The coercive force of the third magnetic thin film 6 using the FeCo film is shown.

As shown in FIG. 5, magnetic transfer from the third magnetic layer 6 using the DyFeCo film to the first magnetic layer 4 using the TbFe film may occur due to the magnitude relationship between the coercive force Hc and the temperature. It can be seen that the temperature range is 370K to 420K. In order to discuss the stability of the interface domain wall domain wall energy in this transfer temperature range, a three-layer magnetic film (first, second, and third layers) at a median value of 395 K in the transfer temperature range was used.
FIGS. 6 and 7 show the reversal state of the sublattice magnetization in the magneto-optical recording medium 1 having the magnetic thin films 4, 5, and 6.

FIG. 6 shows the relationship between the Gd composition (Gd _x Fe _{1 -x} ) and the sublattice magnetization of the magneto-optical recording medium 1 when GdFe of the transition metal dominant (TM-rich) film is used as the second magnetic layer 5. It is a graph which shows an inversion state.

In FIG. 6, "Angle of rate"
The “earth moment” (unit: deg) indicates the magnetization reversal angle, and the x-axis indicates the region (thickness of each layer) of the three-layer magnetic film. “TbFe” is the region (thickness) of the first magnetic layer 4 made of TbFe, and “GdFe” is G
The region of the second magnetic layer 5 composed of dFe, “Dy
“FeCo” indicates a region of the third magnetic thin film 6 made of DyFeCo. The thickness of “GdFe” as the second magnetic layer 5 is 150 Å.
“X = 0.15”, “x = 0.18”, “x = 0.15”
9 "," x = 0.203 "," x = 0.21 "," x =
0.24 ”indicates transition metal dominance (TM-rich)
Gd when GdFe of the film is used as the second magnetic layer 5
The atomic content ratio x in the composition (Gd _x Fe _1-x ) is shown.

FIG. 7 shows rare earth metal dominance (RE-rich).
Gd when GdFe of the film is used as the second magnetic layer 5
5 is a graph showing the reversal state of the sublattice magnetization of the magneto-optical recording medium 1 with respect to the composition (Gd _x Fe _1-x ).

In FIG. 7, "x = 0.27", "x = 0.3
15 "," x = 0.33 "," x = 0.36 "," x =
“0.39” and “x = 0.41” indicate the atomic content in the Gd composition (Gd _x Fe _1-x ) when GdFe of the rare-earth metal dominant (RE-rich) film is used as the second magnetic layer 5. Shows quantitative ratio x.

6 and 7, the magnetization reversal angle is such that the in-plane magnetization direction of the thin film of the magneto-optical recording medium 1 is 0 °, the perpendicular magnetization direction of the thin film is + 90 °, and the perpendicular magnetization direction of the opposite thin film is −. Displayed at 90 °. It is considered that when the magnetization reversal occurs largely in the second magnetic layer 5, most of the interface domain wall energy exists in the second magnetic layer 5 and becomes stable.

In FIG. 6, 24 is close to the compensating composition of the second magnetic layer 5 (composition at which the coercive force Hc becomes infinite at room temperature).
at. % (X = 0.24 in the figure) of the magneto-optical recording medium 1 having the second magnetic layer 5 using the Gd composition, the region where the magnetization is largely reversed is shifted from the second magnetic layer 5 to the first magnetic layer. It is considered that the magnetic field shifts toward the magnetic layer 4 (from “GdFe” to “TbFe” in the figure) and the interface domain wall energy seeps toward the first magnetic layer 4.

Similarly, in FIG. 7, the second magnetic layer 5
27 at. % (X = 0.2 in FIG.
7), in the case of the magneto-optical recording medium 1 having the second magnetic layer 5 using the Gd composition, the region where the magnetization is largely reversed is changed from the second magnetic layer 5 to the first magnetic layer 4 ("GdFe" in FIG. ) To the “TbFe”) side, and it is considered that the interface domain wall energy is seeping out to the first magnetic layer 4 side.

FIG. 8 shows a first magnetic thin film 4 using TbFe.
And a second magnetic layer 5 using GdFe of a transition metal dominant (TM-rich) film and a third magnetic thin film 6 using DyFeCo. It is the graph which compared the temperature dependence of the interface magnetic wall energy at the time of changing the atomic content ratio x of the Gd composition (Gd _x Fe _1-x ).

In FIG. 8, “Gd _.15 Fe _.85 ” is the same as follows when the atomic content ratio x in the Gd composition (Gd _x Fe _{1 -x} ) of the second magnetic layer 5 is x = 0.15. , "Gd _.18 F
e _.82 "is x = 0.18," Gd _.19 Fe _.81 "is x = 0.19,
"Gd _.21 Fe _.79" is x = 0.21, "Gd _.24 Fe _.76"
Indicates the case where x = 0.24.

FIG. 9 shows a first magnetic thin film 4 using TbFe.
And a second magnetic layer 5 using GdFe of a rare-earth metal predominant (RE-rich) film and a third magnetic thin film 6 using DyFeCo. It is the graph which compared the temperature dependence of the interface magnetic wall energy at the time of changing the atomic content ratio x of the Gd composition (Gd _x Fe _1-x ).

In FIG. 9, “Gd _.27 Fe _.73 ” is the same as follows when the atomic content ratio x in the Gd composition (Gd _x Fe _{1 -x} ) of the second magnetic layer 5 is x = 0.27. , "Gd _.30 F
e _.30 "is x = 0.30," Gd _.33 Fe _.67 "is x = 0.33,
"Gd _.36 Fe _.36" is x = 0.36, "Gd _.39 Fe _.61"
Respectively are x = 0.39, "Gd _.41 Fe _.41" as the case of the x = 0.41.

8 and 9, two types of compositions (x = 0.2
4 and x = 0.27), the magneto-optical recording medium 1 using the second magnetic layer 5 does not have such a composition, unlike the magneto-optical recording medium using the second magnetic layer 5 having no such composition. Also in this case, it can be seen that the interface domain wall energy overlaps the Bloch domain wall energy of the first magnetic thin film 4 at a temperature of 395K.

That is, at a temperature of 395 K shown in FIG.
The Gd composition “Gd _.24 F” constituting the second magnetic layer 5
_e.76 ”is“ σ _B of 1st L ”of the first magnetic thin film 4.
at the temperature of 395 K shown in FIG. 9, the Gd composition “Gd _.27 Fe _.73 ” constituting the second magnetic layer 5 is changed to “σ _B ” of the first magnetic thin film 4. of 1st Layer (TbFe) ".

[0050] As a result, 8, close to the compensation composition of the second magnetic layer 5 shown in FIG. 9 "Gd _.24 Fe _.76", "Gd _.27
For the magneto-optical recording medium 1 having a second magnetic layer 5 using a Gd composition of Fe _.73 "region of increasing magnetization reversal of the first magnetic layer 4" σ _B of1st Layer (TbF
e) ”, it is considered that the interface domain wall energy is seeping out to the first magnetic layer 4 side. The domain wall energy σ _w is given by σ _w = approximately 2Ｋ (A ₁ K ₁ ) ^1/2 + (A ₂ K ₂ ) ^1/2 ｝ (2) as in the above equation (2). ₁ : Exchange stiffness constant of the first magnetic thin film A ₂ : Exchange stiffness constant of the second magnetic thin film K ₁ : Effective anisotropic constant of the first magnetic thin film K ₂ : Effective difference of the second magnetic thin film Since it can be expressed by the isotropic constant, it is considered that the interface domain wall shifts to the side where the AK product is smaller. Therefore, by reducing the perpendicular magnetic anisotropy energy of the second magnetic layer 5, the interface domain wall becomes stable.

FIG. 10 shows that rare earth metal dominates (RE-ric
h) G when the film GdFe is used as the second magnetic layer 5
5 is a graph showing the temperature dependence of effective anisotropy with respect to d composition.

In FIG. 10, "x = 0.27", "x = 0.
30, "x = 0.316", "x = 0.3", "x =
“0.36”, “x = 0.39”, and “x = 0.41” respectively indicate the Gd composition (Gd _x ) when GdFe of the rare earth metal (RE-rich) film is used as the second magnetic layer 5. F
e _1-x ) represents the atomic content ratio x.

As is apparent from FIG. 10, the anisotropic energy of the second magnetic layer 5 becomes negative in a temperature range where magnetic transfer can be performed, that is, the second magnetic layer 5 has in-plane magnetic anisotropy. The composition region having a Gd composition of about 32 at. % Or more. In this composition region, most of the interface domain wall exists in the second magnetic layer 5 and becomes stable.

As described above, in the recording thin film medium in which the first and third thin films having perpendicular magnetic anisotropy, which are amorphous thin films made of a rare earth-3d transition metal, are formed with the second magnetic thin film interposed therebetween, The first and third magnetic layers are sequentially magnetically coupled and laminated via the second magnetic layer, and the second magnetic thin film for controlling the coupling state is made of a rare earth metal. The dominant (RE-rich) film has a small exchange energy between rare earth and 3d transition metal,
It can be said that a film having magnetic anisotropy in the in-plane direction at 00 ° C. or more 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 and the 3d transition metal in the molecular field theory, that is, the exchange energy between Gd-Fe in the GdFe intermediate layer, is effective in controlling the temperature characteristics. Bi, Sn in the middle layer
Addition of such an element lowers the compensation temperature and can reduce the exchange energy acting between the rare earth and the transition metal.

FIG. 11 shows a second example of the magneto-optical recording medium 1.
The temperature dependence of the magnetization in the magnetic layer 5 is determined by comparing the case where the rare earth metal dominant (RE-rich) film GdFe is used for the second magnetic layer 5 with the transition metal dominant (TM-rich) film GdFe.
It is the graph which compared the case where Fe was used.

In FIG. 11, "GdFe (J _GdFe = -1.
“7 × 10 ⁻¹⁵ erg” indicates the temperature dependence of magnetization when the exchange energy between Gd and Fe in the second magnetic layer 5 using GdFe of the rare earth metal dominant film is set to −1.7 × 10 ⁻¹⁵ erg. , “GdFe (J _GdFe = −1.2 × 10
^-15 erg "is the second rare earth metal dominant film using GdFe.
The exchange energy between Gd-Fe in the magnetic layer 5 of FIG.
The graph shows the temperature dependence of the magnetization at 1.2 × 10 ⁻¹⁵ erg.

FIG. 12 shows a second example of the magneto-optical recording medium 1.
The temperature dependency of the anisotropy in the magnetic layer 5 is reduced by reducing the exchange energy acting between the rare earth and the 3d transition metal when the rare earth metal dominant (RE-rich) film GdFe is used for the second magnetic layer 5. Of rare earth metal predominant (RE-rich) film
It is the graph which compared with the case where dFe was used.

In FIG. 12, “Ku of GdFe (J
_“GdFe = −1.7 × 10 ⁻¹⁵ erg)” means that the exchange energy between Gd—Fe in the second magnetic thin film 5 using the rare earth metal dominant (RE-rich) film GdFe is −1.7.
The temperature dependence of the true anisotropy when × 10 ⁻¹⁵ erg, “Ku of GdFe (J _GdFe = −1.2 × 10
^-15 erg) is the rare earth metal predominant (RE-rich) film G
Temperature dependence of true anisotropy when the exchange energy between Gd-Fe in the second magnetic thin film 5 using dFe is -1.2 × 10 ⁻¹⁵ erg, “Ku−2πMs ² o”
“f GdFe (J _GdFe = −1.2 × 10 ⁻¹⁵ erg)” means that the exchange energy between Gd—Fe in the second magnetic thin film 5 using GdFe of the rare earth metal dominant (RE-rich) film is −1. Temperature dependence of effective anisotropy at 2 × 10 ⁻¹⁵ erg, and “Ku−2πMs ² of
GdFe (J _GdFe = −1.7 × 10 ⁻¹⁵ erg) ”is the second rare earth metal dominant (RE-rich) film using GdFe.
Temperature dependence of the effective anisotropy when the exchange energy between Gd-Fe in the magnetic thin film 5 is -1.7 × 10 ⁻¹⁵ erg.

FIGS. 11 and 12 show that the exchange energy between Gd and Fe is changed from -1.7 × 10 ^-15 erg to -1.2 × 1.
The graph shows the temperature characteristics of magnetization and anisotropy when the temperature is reduced to 0 ^-15 erg. As can be seen from comparison with FIGS. 3 and 4 described above, the magnetization and effective anisotropy vary greatly. I have. When the exchange energy between Gd-Fe is reduced, the magnetization decreases almost linearly with the temperature rise, and as a result, the effective anisotropy draws a convex curve and increases sharply. .

FIG. 13 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 which is the intermediate layer used in the comparison of FIG. The second magnetic layer 5 has a rare-earth metal dominant (RE-r) with a reduced exchange energy acting between the rare earth and the 3d transition metal.
ich) is a graph comparing with the case of using a film.

In FIG. 13, “2nd Layer (J _GdFe
= −1.7 × 10 ⁻¹⁵ erg) ”means rare earth metal dominant (RE−
rich) in the second magnetic thin film 5 using the film.
Temperature dependence of the interface domain wall energy when the exchange energy between Fe is -1.7 × 10 ^-15 erg, "2nd
“Layer (J _GdFe = −1.2 × 10 ⁻¹⁵ erg)” indicates that the exchange energy between Gd—Fe in the second magnetic thin film 5 using the rare-earth dominant (RE-rich) film is −1.2 ×.
The temperature dependence of the interface domain wall energy at 10 ⁻¹⁵ erg is shown.

As is apparent from FIG. 13, in the medium using the intermediate layer (second magnetic thin film 5) having a reduced exchange energy acting between the rare earth metal and the 3d transition metal, the interface domain wall energy accompanying the temperature rise is reduced. It can be seen that the degree of decrease 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 the magnetization is expressed by (H _c1 −H _w1 H _c1 : the 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 -
_Hw1 ) is negative and the absolute value is large, the better the transferability.

The (H _c1 −H _w1 ) of the two types of media used in the comparison of FIG. 2 and the (H _c1 − of the medium using the intermediate layer with a reduced exchange energy acting between the rare earth and the 3d transition metal are used.
FIG. 14 compares the temperature changes of H _w1 ).

In FIG. 14, “H _c1 −H _w1 ” (unit: kO
e) is a 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 _GdFe = −1.7 × 10 ⁻¹⁵ erg) ”means that the exchange energy between Gd—Fe in a medium using a transition metal dominant (TM-rich) film as the second magnetic thin film 5 is −1.7 ×. 1
When (H _c1 −H _w1 ) is set to 0 ^-15 erg, “RE-r
ich 2nd Layer (J _GdFe = −1.7 × 10
^-15 erg) when the exchange energy between Gd 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. _c1 −H _w1 ) and “RE-rich 2nd
“Layer (J _GdFe = −1.2 × 10 ⁻¹⁵ erg)” indicates that the exchange energy between Gd—Fe in a medium using a rare-earth metal dominant (RE-rich) film as the second magnetic thin film 5 −
(H _c1 −H _w1 ) in the case of 1.2 × 10 ⁻¹⁵ erg is shown.

As is apparent from FIG. 14, 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. Since (H _c1 −H _w1 ) decreases in the order of the medium using the intermediate layer with further reduced exchange energy, it can be said that the transferability of magnetization is improved in this order.

As described above, the rare earth metal predominant (RE-rich) film used for the second magnetic layer 5 is an amorphous thin film having magnetic anisotropy in a plane or in a vertical direction at room temperature. By using Fe or FeCo as the transition metal, and further adding elements such as Bi and Sn, a film in which the exchange energy acting between the rare earth and the 3d transition metal is reduced is effective for improving the recording characteristics. It can be said.

[0070]

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 formed at least in the high temperature region. , A rare earth metal dominant composition having in-plane magnetic anisotropy by adding metals such as Bi and Sn to form a film having a certain film thickness, thereby suppressing the interface magnetic wall energy near room temperature and reducing the temperature near T _1. The effect of keeping the domain wall energy large can be obtained. Thus, work to stabilize the magnetic domain wall at room temperature, and it is possible to improve the stability of the transfer of the recording magnetic domain at temperatures T ₁ neighborhood. 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 shows the temperature dependence of the magnetization in the second magnetic layer constituting the magneto-optical recording medium when the GdFe of the rare earth metal dominant film of the second magnetic layer and the GdFe of the transition metal dominant film are used. It is the graph which compared with FIG.

FIG. 4 shows the temperature dependence of the anisotropy in the second magnetic layer constituting the magneto-optical recording medium, when the GdFe of the rare earth metal dominant film is used for the second magnetism and the GdFe of the transition metal dominant film.
Fig. 6 is a graph for comparison in the case of using.

FIG. 5 is a cross-sectional view of the magneto-optical recording medium shown in FIG.
5 is a graph showing a temperature change of coercive force Hc of a first magnetic thin film using a film and a third magnetic thin film using a DyFeCo film.

FIG. 6 is a graph showing the inversion state of the sublattice magnetization of the magneto-optical recording medium with respect to the Gd composition (Gd _x Fe _1-x ) when GdFe of the transition metal dominant film is used for the second magnetic layer.

FIG. 7 is a graph showing the inversion state of the sublattice magnetization of the magneto-optical recording medium with respect to the Gd composition (Gd _x Fe _1-x ) when GdFe of the rare earth metal dominant film is used for the second magnetic layer.

FIG. 8 shows a magneto-optical recording medium including a first magnetic thin film using TbFe, a second magnetic layer using GdFe as a transition metal dominant film, and a third magnetic thin film using DyFeCo; Composition of the magnetic layer (Gd _x F
5 is a graph comparing the temperature dependence of the interface domain wall energy when the atomic content ratio x of e _1-x ) is changed.

FIG. 9 shows a first magnetic thin film using TbFe, a second magnetic layer using GdFe of a rare earth metal predominant film, and DyFeCo.
In a magneto-optical recording medium provided with a third magnetic thin film using a magnetic material, a Gd composition (Gd _x Fe
₆ is a graph comparing the temperature dependence of the interface domain wall energy when the atomic content ratio x of _1-x ) is changed.

FIG. 10 Gd of rare earth metal predominant (RE-rich) film
6 is a graph showing the temperature dependence of the effective anisotropy with respect to the Gd composition when Fe is used as the second magnetic layer 5.

FIG. 11 shows the temperature dependence of the magnetization in the second magnetic layer constituting the magneto-optical recording medium, in the case where GdFe of the rare earth metal dominant (RE-rich) film of the second magnetic layer is used, and in the case where the rare earth metal is 3d transition. FIG. 9 is a graph comparing a case where GdFe of a rare earth metal predominant (RE-rich) film with a lower exchange energy acting between metal groups is used.

FIG. 12 shows the temperature dependence of the anisotropy in the second magnetic layer constituting the magneto-optical recording medium, when the GdFe of the rare earth metal dominant film is used for the second magnetism and between the rare earth metal and the 3d transition metal. 7 is a graph comparing with the case where GdFe of the rare earth metal dominant film having a lower exchange energy acting on GdFe is used.

FIG. 13 shows the temperature dependency of the interface domain wall energy between the case where a rare earth metal dominant (RE-rich) film is used for the second magnetic layer which is the intermediate layer used in the comparison of FIG. 7 is a graph comparing a case where a rare earth metal dominant (RE-ich) film having a reduced exchange energy acting between a rare earth and a 3d transition metal is used for the magnetic layer 5 of FIG.

FIG. 14 shows the light using the second magnetic layer of the two types of magneto-optical recording media used in the comparison of FIG. 2, in which the exchange energy between the (H _c1 −H _w1 ), the rare earth and the 3d transition metal is reduced. 4 is a graph comparing temperature changes of (H _c1 −H _w1 ) of a magnetic recording medium.

FIG. 15 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 (2)

[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 are rare-earth elements having perpendicular magnetic anisotropy. -3d transition metal, and is magnetically coupled via the second magnetic thin film. The second magnetic thin film has a small exchange energy with the rare earth-3d transition metal. Rare earth metal having magnetic anisotropy in the in-plane direction at 100 ° C. or more (RE-rich)
A magneto-optical recording medium comprising a film. 2. The second magnetic thin film is an amorphous thin film having in-plane or vertical magnetic anisotropy at room temperature, wherein Gd (gadolinium) is used as a rare earth element and Fe is used as a 3d transition metal.
By using (iron) or FeCo (iron-cobalt alloy) and further adding Bi (bismuth) and Sn (tin) as other metal elements, the exchange energy acting between the rare earth and the 3d transition metal was reduced. 2. The magneto-optical recording medium according to claim 1, wherein: