JP2003281795A - Magneto-optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve jitter characteristics by making magnetic domain wall movement prompt. <P>SOLUTION: In a first magneto-optical recording medium 10A, a first magnetic layer 13 is made of a material using a Gd-Fe film or a Gd-Fe-Co film as a base so that a magnetic field normalized based on saturation magnetization of a magnetic domain wall driving field can be >1, and an element concentration ratio (in percent) of Gd to Fe or Fe-Co is set in a range of 28.0≤Gd≤29.0. A second magnetic layer 14 is made of a material using a Tb-Fe film or a Dy-Fe film as a base, to which a non-magnetic element such as Al and Cr, and Co are added. A third magnetic layer 15 is made of a material using a Tb-Fe-Co film or a Dy-Fe-Co film as a base, and an element concentration ratio (in percent) of Tb or Dy to Fe-Co is set in a range of 23.5≤Tb≤25.5 or 25.5≤Dy≤28.5. <P>COPYRIGHT: (C)2004,JPO

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 that reproduces an information signal while causing domain wall movement by irradiating a laser beam.

[0002]

2. Description of the Related Art In a magneto-optical recording system, a ferrimagnetic thin film is locally heated to near a Curie point or a compensation point, and the coercive force of this portion is reduced so that an external information signal to be recorded can be obtained. The basic principle is to reverse the direction of the magnetization in the direction of the applied recording magnetic field from. In the magneto-optical recording / reproducing in which the portion where the magnetization is reversed, that is, the information bit forms a magnetic domain, and the magnetic domain is used to read it, the recording bit length is shortened, that is, the information signal is formed in the form of the magnetic domain in order to improve recording density. It is necessary to reduce the size of the magnetic domain when recording is performed with. However, the reproduction resolution of the magnetic domain (information signal) is almost determined by the wavelength λ of the laser light source of the reproduction optical system and the numerical aperture NA of the objective lens, and the spatial frequency 2NA / λ is the reproduction limit. Therefore, in order to increase the recording density, shorten the wavelength λ of the laser light source,
It is conceivable to use a high NA objective lens to reduce the spot diameter of the laser beam on the reproducing device side. However, the wavelength of the laser light source currently in practical use is 6
It is only about 40 nm, and when a high NA objective lens is used, the depth of focus becomes shallow, and precision is required for the distance between the objective lens and the magneto-optical recording medium (optical disk or optical card). The accuracy becomes severe. Therefore, the NA of the objective lens cannot be made very high, and the NA of the objective lens that can be put to practical use is at most 0.6. That is, there is a limit in improving the recording density by the wavelength λ of the laser light source and the numerical aperture NA of the objective lens.

Therefore, as a means for solving the problem of the recording density defined by such a reproducing condition, a magnetic recording medium having a three-layer magnetic layer structure (= magneto-optical recording medium)
There is a signal reproducing method of a magnetic recording medium for reproducing the data (for example, see Patent Document 1). There is also a magnetic recording medium (= magneto-optical recording medium) having a four-layer magnetic layer structure (for example, refer to Patent Document 2).

[0004]

[Patent Document 1] Japanese Patent Laid-Open No. 11-86372 (4th
(Page, Fig. 1)

[0005]

[Patent Document 2] Japanese Patent Laid-Open No. 2000-187898 (page 3-4, FIG. 1)

FIG. 21 is a diagram for explaining an example of a conventional magneto-optical recording medium. (A) schematically shows the layer structure of the magneto-optical recording medium, and (b) shows when a laser beam is irradiated. FIG. 22 is a diagram showing the temperature distribution on the magneto-optical recording medium, FIG. 22 is a diagram for explaining another example of the conventional magneto-optical recording medium, and FIG. 22A is a schematic diagram showing the layer structure of the magneto-optical recording medium. ,
(B) is a diagram showing a temperature distribution on the magneto-optical recording medium when a laser beam is irradiated.

An example of the conventional magneto-optical recording medium 110 shown in FIG.
No. 2), and FIG.
Another example of the conventional magneto-optical recording medium 120 shown in FIG. 1 is disclosed in the above-mentioned Patent Document 2 (Japanese Patent Laid-Open No. 2000-187898). explain.

First, as shown in FIGS. 21A and 21B, in the conventional magneto-optical recording medium 110, the first to third magnetic layers 111 to 113 are exchange-coupled at room temperature and sequentially laminated. The first magnetic layer 111, which is provided on the side irradiated with the reproducing laser beam and serves as the domain wall motion layer, is
The second magnetic layer 112 is made of a magnetic film having a domain wall coercive force relatively smaller than that of the third magnetic layer 113 serving as a recording layer, and the second magnetic layer 112 has a lower Curie temperature than that of the first magnetic layer 111 and the third magnetic layer 113. It consists of a membrane.

More specifically, the above-mentioned first to third magnetic layers 111 to 113 are made of, for example, Pr, Nd, Sm, E.
10 to 40 atom% of one or more rare earth metal elements such as u, Gd, Tb, Dy, Ho and Er,
It is composed of a rare earth-iron group amorphous alloy composed of 60 to 90 atomic% of one or more iron group elements such as Fe, Co and Ni. In addition, in order to improve the corrosion resistance and the like, these alloys may contain Cr, Mn, Cu, T
It is described that elements such as i, Al, Si, Pt and In may be added in small amounts.

The magneto-optical recording medium 11 constructed as described above.
0, the laser beam is applied to the first magnetic layer 1 during recording.
By recording an information signal in the third magnetic layer 113 by a magnetic head (not shown) while irradiating from the 11 side, it is preserved as a magnetization reversal region in the arrow direction (hereinafter referred to as a magnetic domain),
Furthermore, when the laser beam is not irradiated after recording, the magnetic domain recorded in the third magnetic layer 113 is exchange-coupled to the first magnetic layer 111 via the second magnetic layer 112. At this time, the first
The vertical arrow AS in the third magnetic layers 111 to 113 represents the direction of atomic spin. A domain wall DW is formed at the boundary between regions where the spin directions are opposite to each other.

Here, when the first magnetic layer 111 is irradiated with a laser beam during reproduction, the medium temperature between the position X1 and the position X2 shown in the figure with respect to the laser beam is equal to or higher than the Curie temperature Ts of the second magnetic layer 112. Reach Accordingly, in the region between the position X1 and the position X2, the second magnetic layer 1
Since the temperature of 12 has been raised to the Curie temperature Ts or higher, the magnetization of the second magnetic layer 112 disappears, and the first magnetic layer 111
The exchange coupling between the third magnetic layer 113 and the third magnetic layer 113 is broken, and this region is called a bond breaking region.

Then, the first magnetic layer 11 is formed in the bond breaking region.
When the domain wall DW existing in 1 enters, the domain wall DW moves toward the peak of temperature in the first magnetic layer 111 as indicated by the arrow, so that the domain wall movement DWM occurs, and along with this domain wall movement DWM. The magnetic domains exchange-coupled in the first magnetic layer 111 are expanded and read by the reproducing laser beam. On the other hand, since the coercive force (domain wall coercive force) of the third magnetic layer 113, which is the recording layer, is sufficiently large, the third magnetic layer 11
The domain wall in 3 remains in the recorded state without moving. As a result, the recording density is remarkably improved by enlarging and reproducing the minute magnetic domain that cannot be reproduced by the normal reproduction resolution.

Next, as shown in FIGS. 22A and 22B, another conventional magneto-optical recording medium 120 has one more magnetic layer than the above-described magneto-optical recording medium 110. By forming a film by the laser beam irradiation, particularly, when the laser beam is irradiated, the domain wall moves from the front (direction of arrow I1) in the moving direction of the laser beam in the temperature domain where the domain wall can move, and from the back (direction of arrow I2) in the moving direction. This is intended to improve the performance so that only the movement of the domain wall from the front in the moving direction (the direction of arrow I1) can be expanded and read out by the spot of the laser beam without the movement of the domain wall occurring together.

In this magneto-optical recording medium 120, the first to fourth magnetic layers 121 to 124 are exchange-coupled at room temperature and sequentially laminated, and the domain wall displacement layer is provided on the side where the reproducing laser beam is irradiated. The first magnetic layer 121 has a domain wall coercive force smaller than that of the second to fourth magnetic layers 122 to 124 at room temperature, and the second magnetic layer 122 has the first magnetic layer at room temperature.
The domain wall energy density is higher than that of the magnetic layer 121, the Curie temperature of the third magnetic layer 113 is higher than room temperature, and lower than the Curie temperatures of the first, second, and fourth magnetic layers 121, 122, and 124. The 4-magnetic layer 124 is configured as a recording layer.

More specifically, the above-mentioned first to fourth magnetic layers 121 to 124 are substantially the same as the above-mentioned first to third magnetic layers 111 to 113 in the magneto-optical recording medium 110, for example, Pr, Nd, Sm, Eu, Gd, Tb, Dy, H
One or two or more rare earth metal elements such as o and Er are composed of 10 to 40 atomic%, and one or two or more kinds of iron group elements such as Fe, Co and Ni are composed of 60 to 90 atomic%. It is composed of a rare earth-iron group amorphous alloy. In addition, in order to improve corrosion resistance, etc., C should be added to these alloys.
It is described that elements such as r, Mn, Cu, Ti, Al, Si, Pt and In may be added in small amounts. Furthermore, Pt
/ C, Pd / Co and other platinum group-iron group periodic structure films, platinum group-iron group alloy films, antiferromagnetic materials such as Co-Ni-O and Fe-Rh alloys, and materials such as magnetic garnet. It states that it can be used.

The magneto-optical recording medium 12 constructed as described above.
0, the laser beam is applied to the first magnetic layer 1 during recording.
An information signal is recorded in the fourth magnetic layer 124 by a magnetic head (not shown) while irradiating from the 21st side, so that the magnetic domains are preserved as magnetic domains in the direction of the arrow. Further, after recording, when the laser beam is not irradiated, the fourth magnetic layer 124 The magnetic domain recorded in the first magnetic layer 12 via the second and third magnetic layers 122 and 123.
Exchange coupled to 1. At this time, the first to fourth magnetic layers 1
The vertical arrows AS in 21 to 124 represent the directions of atomic spins. A domain wall DW is formed at the boundary between regions where the spin directions are opposite to each other.

Here, when the first magnetic layer 121 is irradiated with a laser beam during reproduction, the medium temperature is higher than the Curie temperature Ts of the third magnetic layer 123 between the position X1 and the position X2 shown in the figure with respect to the laser beam. Reach Accordingly, in the region between the position X1 and the position X2, the third magnetic layer 1
Since the temperature of 12 is raised to the Curie temperature Ts or higher, the magnetization of the third magnetic layer 123 disappears, and the exchange coupling between the first and second magnetic layers 121 and 122 and the fourth magnetic layer 124 is broken. This region is referred to as the bond cleavage region.

When the domain wall DW existing in the first and second magnetic layers 121 and 122 enters the bond breaking region,
Since the domain wall DW moves toward the temperature peak in the first and second magnetic layers 121 and 122 as shown by the arrows, the domain wall movement DWM occurs, and the domain wall movement DWM causes the inside of the first magnetic layer 121 to move. The magnetic domains exchange-coupled with each other are expanded and read by the reproducing laser beam. On the other hand, the coercive force (domain wall coercive force) of the fourth magnetic layer 124, which is the recording layer, is sufficiently large, so that the domain wall in the fourth magnetic layer 124 remains in the recorded state without moving. As a result, the recording density is remarkably improved by enlarging and reproducing the minute magnetic domain that cannot be reproduced by the normal reproduction resolution.

Incidentally, the above-mentioned Japanese Patent Laid-Open No. 2000-187898.
In the publication, the domain wall motion DWM is described as the first and second magnetic layers 12
However, since the second magnetic layer 122 is generally formed to be extremely thin, the second magnetic layer 122 functions as a domain wall motion layer or exchange coupling is performed. It is not clear whether or not it functions as a control layer, and therefore at least the magnetization of the third magnetic layer 123 disappears due to the temperature rise due to the irradiation of the laser beam during reproduction, and the exchange-coupled magnetic domains in the first magnetic layer 121 are expanded. It can be considered that it causes the domain wall movement.

[0020]

By the way, the conventional magneto-optical recording media 110, 1 shown in FIGS. 21 and 22, respectively.
In FIG. 20, the domain expansion reproduction technique by the domain wall displacement DWM is an effective technique for realizing an ultra-high density recording medium, but there is a problem of a deviation of a reproduction signal peculiar to the domain wall displacement reproduction on the time axis, so-called jitter characteristic deterioration. There is. In order to improve this jitter characteristic, it is necessary to make the start timing of the domain wall motion DWM agile and to shorten the time required to complete the domain wall motion DWM.

However, the conventional magneto-optical recording medium 11
1st to 3rd magnetic layers 111 to 113 and 1st in 0, 120
As described above, in each of the magnetic compositions of the fourth magnetic layers 121 to 124, one kind or two or more kinds of rare earth metal elements are 10 to 40 atomic% in each magnetic layer, and Fe,
Only one type or two or more types of iron group elements such as Co and Ni are composed of 60 to 90 atom%, and a sample was prepared based on this, and an experiment was attempted. Did not improve the jitter characteristics of.

Therefore, according to the present invention, in a magneto-optical recording medium having a magnetic layer of a three-layer structure and a magneto-optical recording medium having a magnetic layer of a four-layer structure, particularly, a first magnetic layer serving as a domain wall displacement layer and recording are provided. By clarifying the characteristic change due to the exchange interaction between the layer and the third magnetic layer or the fourth magnetic layer with respect to the composition change of each layer, and by strictly combining the composition ranges, Magnetic domain smaller than 1 μm (record mark)
In the temperature region where reproduction is performed by moving the domain wall, the first magnetic layer serving as the domain wall moving layer is changed from the third magnetic layer or the fourth magnetic layer serving as the recording layer in the temperature range where reproduction is performed by the domain wall moving. It is intended to provide a high-density magneto-optical recording medium capable of improving the jitter characteristic and simultaneously improving the recording magnetic field sensitivity by reducing the stray magnetic field leaking to the layer.

[0023]

The present invention has been made in view of the above problems, and the first invention is to sequentially form first, second and third magnetic layers from the laser beam irradiation side. In addition, after recording the information signal in the form of magnetic domains in the third magnetic layer having an easy axis of magnetization in the vertical direction by an external magnetic field while irradiating the laser beam during recording, the magnetic domains form the second magnetic layer. Exchange-coupled to the first magnetic layer through the magnetic field, and the magnetization of the second magnetic layer disappears due to a temperature rise caused by irradiation of the laser beam during reproduction, so that the magnetic domains exchange-coupled in the first magnetic layer are expanded. In the magneto-optical recording medium that causes the domain wall motion in the first magnetic layer, the first magnetic layer is a Gd-Fe film or a Gd-Fe film so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is greater than 1.
-A film based on a Co film is formed, and F of Gd is formed.
The element concentration ratio (at.% ratio) to e or Fe-Co is set in the range of 28.0≤Gd≤29.0, and the second magnetic layer is based on a Tb-Fe film or a Dy-Fe film. Film is formed by adding a non-magnetic element such as Al or Cr or Co, and the third magnetic layer is a material based on a Tb-Fe-Co film or a Dy-Fe-Co film. Film formation,
In addition, the element concentration ratio (at.% Ratio) of Tb or Dy to Fe—Co is 23.5 ≦ Tb ≦ 25.5 or 25.
The Curie temperatures Tc11 and Tc of the first, second and third magnetic layers are adjusted by setting the range of 5 ≦ Dy ≦ 28.5 and adjusting the amount of Co or non-magnetic element added to each magnetic layer.
12, Tc13 is set so that Tc13>Tc11> Tc12 is set, which is a magneto-optical recording medium.

In the second invention, the first, second, third and fourth magnetic layers are sequentially formed from the laser beam irradiation side,
In addition, after recording the information signal in the form of magnetic domains on the fourth magnetic layer having an easy axis of magnetization in the vertical direction by an external magnetic field while irradiating the laser beam during recording, the magnetic domains are changed to the second and third magnetic layers. The magnetic domains exchange-coupled in the first magnetic layer are exchange-coupled to the first magnetic layer through a layer, and at least the magnetization of the third magnetic layer disappears due to a temperature rise caused by irradiation of the laser beam during reproduction. In the magneto-optical recording medium in which the domain wall motion is caused to expand, the first magnetic layer is Gd-Fe so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is larger than 1.
Film or a material based on a Gd-Fe-Co film is formed, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is in the range of 28.0≤Gd≤29.0. And the second and third magnetic layers are formed of a Tb-Fe film or D
A material based on the y-Fe film is used to form a film by adding a non-magnetic element such as Al and Cr or Co, and the fourth magnetic layer is a Tb-Fe-Co film or a Dy-Fe-Co film. A film-based material is formed, and Tb or Dy Fe-
The element concentration ratio (at.% Ratio) to Co is 23.5 ≦ T
It is set in the range of b ≦ 25.5 or 25.5 ≦ Dy ≦ 28.5 and the addition amount of Co or a non-magnetic element is adjusted to each magnetic layer to adjust the first, second, third, Curie temperatures Tc21, Tc22, Tc23, Tc24 of the fourth magnetic layer
Is set to satisfy Tc24>Tc21>Tc22> Tc23.

A third aspect of the invention is to form the first, second and third magnetic layers in order from the laser beam irradiation side, and
During recording, an information signal is recorded in the form of magnetic domains on the third magnetic layer having an easy axis of magnetization in the vertical direction by irradiating the laser beam with the external magnetic field, and then the magnetic domains are recorded via the second magnetic layer. The second magnetic layer is exchange-coupled to the first magnetic layer and is heated by the irradiation of the laser beam during reproduction.
In a magneto-optical recording medium in which the magnetization of a magnetic layer disappears to cause domain wall movement so as to expand the exchange-coupled magnetic domains in the first magnetic layer, the first magnetic layer converts a domain wall driving magnetic field into saturation magnetization. Gd-Fe film or Gd-Fe-Co so that the normalized magnetic field standardized based on
A film-based material is formed, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is 28.
It is set in the range of 0 ≦ Gd ≦ 29.0, and the second magnetic layer is made of a material based on a Tb-Fe film or a Dy-Fe film, and a non-magnetic element such as Al or Cr or Co is added. Then, the third magnetic layer is formed of a Tb-Fe-Co film and a G layer.
Stable when the magnetization directions of the two-layer film are opposite to each other in the temperature region where the two-layer film including the d-Fe-Co film is formed and the reproduction is performed by the domain wall movement in the first magnetic layer. The magneto-optical recording medium is characterized in that the antiparallel coupling is maintained.

Further, in the fourth invention, the first, second, third and fourth magnetic layers are sequentially formed from the laser beam irradiation side,
In addition, after recording the information signal in the form of magnetic domains on the fourth magnetic layer having an easy axis of magnetization in the vertical direction by an external magnetic field while irradiating the laser beam during recording, the magnetic domains are changed to the second and third magnetic layers. The magnetic domains exchange-coupled in the first magnetic layer are exchange-coupled to the first magnetic layer through a layer, and at least the magnetization of the third magnetic layer disappears due to a temperature rise caused by irradiation of the laser beam during reproduction. In the magneto-optical recording medium in which the domain wall motion is caused to expand, the first magnetic layer is Gd-Fe so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is larger than 1.
Film or a material based on a Gd-Fe-Co film is formed, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is in the range of 28.0≤Gd≤29.0. And the second and third magnetic layers are formed of a Tb-Fe film or D
A material based on the y-Fe film is used to form a film by adding a non-magnetic element such as Al or Cr or Co. The fourth magnetic layer is formed of a Tb-Fe-Co film and a Gd-Fe-Co film. Anti-parallel coupling, which is stable when the directions of magnetization of the two-layer film are opposite to each other in the temperature region where reproduction is performed by domain wall movement in the first magnetic layer, and the two-layer film is formed by It is a magneto-optical recording medium characterized in that

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a magneto-optical recording medium according to the present invention will be described below in detail with reference to FIGS.

First, the layer structure of the magneto-optical recording medium according to the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view schematically showing the layer structure of a first magneto-optical recording medium according to the present invention, and FIG. 2 is a schematic view of the layer structure of a second magneto-optical recording medium according to the present invention. It is the sectional view shown.

As shown in FIG. 1, the first magneto-optical recording medium 10A according to the present invention has three magnetic layers similar to the magneto-optical recording medium 110 (FIG. 21) of the example described in the prior art. With the structure, the domain wall motion is generated similarly to the conventional magneto-optical recording medium 110. However, in the first magneto-optical recording medium 10A according to the present invention, the composition of each magnetic layer is the same as that of the conventional magneto-optical recording medium. By making it more strict than that of the recording medium 110, the domain wall movement can be swiftly performed, and the jitter characteristic, which is one of the reproduction signal characteristics, can be greatly improved.

Therefore, the first magneto-optical recording medium 10A according to the present invention is also the conventional magneto-optical recording medium 110 described above.
Similarly to (FIG. 21), first, second, and third magnetic layers 13, 14, and 15 are sequentially formed from the laser beam irradiation side,
In addition, an information signal is recorded in the form of magnetic domains in the third magnetic layer 15 having an easy axis of magnetization in the vertical direction by an external magnetic field while irradiating the laser beam during recording, and then the magnetic domains are changed to the second magnetic layer 14. Through the first magnetic layer 13
Is exchange-coupled with the first magnetic layer 13 and the magnetization of the second magnetic layer 14 disappears due to a temperature rise caused by irradiation of the laser beam during reproduction, and a domain wall movement is generated so as to expand the exchange-coupled magnetic domain in the first magnetic layer 13. It is what makes me.

That is, the first magneto-optical recording medium 10A according to the present invention is formed as an optical disk having a disk-shaped outer shape or a card-shaped optical card, and is configured to record and reproduce information signals at an extremely high density. ing.

In the above-described first magneto-optical recording medium 10A, the transparent first dielectric film serving as the protective film or the multiple interference film is formed on the light-transmissive substrate 11 formed by using the transparent glass plate or the transparent polycarbonate. The first magnetic layer 13, the second magnetic layer 14, and the third magnetic layer 15 are sequentially laminated in the vacuum by, for example, continuous sputtering or the like via the body layer 12 to form a magnetic layer having a three-layer structure. . Furthermore, the third magnetic layer 1
5, a second dielectric layer 16 made of a non-magnetic metal film or a dielectric film is formed, and a protective layer 17 made of a UV curable resin or the like is formed on the second dielectric layer 16 if necessary. Is configured. At this time, the first magneto-optical recording medium 10A
Irradiation of the laser beam to the first magnetic layer 13 to the third magnetic layer 15 is performed from the light transmissive substrate 11 side.

Here, in the first magneto-optical recording medium 10A, of the magnetic layers of the first to third magnetic layers 13 to 15 having the three-layer structure, the first magnetic layer 1 on the laser beam irradiation side.
Reference numeral 3 is a film having a small magnetic anisotropy in order to facilitate the movement of the domain wall due to the temperature gradient created by the irradiation of the laser beam, and functions as a domain wall moving layer.

The first magnetic layer 13 is formed as a film having a direction of easy magnetization in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of a heavy rare earth-iron group metal, which is a so-called vertical magnetization film. , Gd-Fe film or Gd-Fe
-A material based on a Co film is used. And
As will be described later, the domain wall moving operation in the first magnetic layer 13 is W
The film is formed so that it can be handled in the case where the limit of Alker is greatly exceeded. Specifically, the iron group metal (Fe or Fe) of the heavy rare earth (Gd) in the first magnetic layer 13 is specifically formed.
The element concentration ratio (at.% Ratio) to —Co) is 28.0.
By setting the range of ≦ Gd ≦ 29.0, the film is formed so that the standardized magnetic field obtained by standardizing the domain wall drive magnetic field based on the saturation magnetization is larger than 1. About the range of the element concentration ratio Will be described later. At this time, C in the first magnetic layer 13
The Curie temperature Tc11 of the first magnetic layer 13 is adjusted by adjusting the addition amount of o and further adding a nonmagnetic element such as Al and Cr. The non-magnetic element such as Al and Cr added here has a relatively low atomic number in the periodic table of the elements.

Next, the second magnetic layer 14 is formed into the third magnetic layer 15
To function as a film for controlling the exchange coupling force when the magnetic domain (recording mark) is transferred to the first magnetic layer 13. The second magnetic layer 14 is also formed as a film having a magnetization easy direction in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of a heavy rare earth-iron group metal that serves as a so-called perpendicular magnetization film, and Tb. Using a material based on a -Fe film or a Dy-Fe film, a nonmagnetic element such as Al or Cr or Co is added to form a film while adjusting the Curie temperature Tc12 of the second magnetic layer 14.

Next, in the third magnetic layer 15, a magnetic domain (magnetization reversal) is formed on a film surface having an easy axis of magnetization in the direction perpendicular to the information signal by an external magnetic field such as a magnetic head (not shown) while irradiating a laser beam during recording. Area)), and has a coercive force sufficient to stably hold the recorded magnetic domain at room temperature and a Curie temperature Tc13 suitable for recording an information signal. It is necessary and functions as a recording layer (memory layer).

The third magnetic layer 15 is also formed as an amorphous thin film composed of a heavy rare earth-iron group metal which is a film having a magnetization easy direction in the vertical direction (direction perpendicular to the film surface), that is, a so-called perpendicular magnetization film. , Tb-Fe-Co film or Dy
A material based on a —Fe—Co film is used.
The Curie temperature Tc13 of the third magnetic layer 15 is adjusted by adding a non-magnetic element such as 1 or Cr, and the iron group metal (Fe) of heavy rare earth (Tb or Dy) in the third magnetic layer 15 is adjusted.
The element concentration ratio (at.% Ratio) to -Co) is 23.5
The range of ≦ Tb ≦ 25.5 or 25.5 ≦ Dy ≦ 28.5 is set, and the range of the element concentration ratio will be described later.

Then, the first, second and third magnetic layers 13 are taken into consideration in consideration of the temperature rising state at the time of recording and reproducing by the laser beam with respect to the first magneto-optical recording medium 10A having the above structure. , 14 and 15 Curie temperatures Tc11 and Tc
12, Tc13 is about 530K, about 420K, about 590
It is desirable to be near K. Here, the Curie temperatures Tc11 of the first, second and third magnetic layers 13, 14, 15 are
Tc12 and Tc13 can increase the Curie temperature by increasing the amount of Co added in each magnetic layer,
On the other hand, the Curie temperature can be lowered by increasing the addition amount of a nonmagnetic element such as Al or Cr that does not significantly change the magnetic characteristics of each magnetic layer. The above Curie temperatures Tc11, Tc12, and Tc13 are adjusted to Tc13 by adjusting the addition amount of the magnetic element.
>Tc11> Tc12 is set.

Furthermore, the first, second and third magnetic layers 13, 1
It is desirable that the film thicknesses t11, t12, and t13 of 4 and 15 are set to about 30 nm, about 10 nm, and about 60 to 80 nm, respectively.

Next, as shown in FIG. 2, the second magneto-optical recording medium 20A according to the present invention is magnetic like the magneto-optical recording medium 120 (FIG. 22) of another example described in the prior art. A conventional magneto-optical recording medium 1 having a four-layer structure
Similar to 20, the irradiation of the laser beam causes only the movement of the domain wall from the front in the moving direction of the laser beam in the temperature region (about 430K to about 490K) in which the domain wall can move. 2 magneto-optical recording medium 2
At 0 A, the composition of each magnetic layer is the same as that of the conventional magneto-optical recording medium 120.
By making it more rigorous, the domain wall movement can be made quicker, and the jitter characteristic, which is one of the reproduction signal characteristics, can be greatly improved.

Therefore, the second magneto-optical recording medium 20A according to the present invention is also the conventional magneto-optical recording medium 120 described above.
Similarly to (FIG. 22), the first, second, third and fourth magnetic layers 23, 24, 25 and 26 are sequentially formed from the laser beam irradiation side, and the laser beam is irradiated during recording. Meanwhile, an information signal is recorded in the form of magnetic domains in the fourth magnetic layer 26 having an easy axis of magnetization in the vertical direction by an external magnetic field, and then the magnetic domains are recorded via the second and third magnetic layers 24 and 25. One magnetic layer 23 is exchange-coupled, and at the time of reproduction, the magnetization of at least the third magnetic layer 25 disappears due to a temperature rise caused by irradiation with the laser beam, so that the exchange-coupled magnetic domains in the first magnetic layer 23 are expanded. It causes the domain wall movement.

That is, the second magneto-optical recording medium 20A according to the present invention is formed as an optical disk having a disk-shaped outer shape or a card-shaped optical card, and is configured to record / reproduce information signals at an extremely high density. ing.

In the above-mentioned second magneto-optical recording medium 20A, the transparent first dielectric film serving as the protective film or the multiple interference film is formed on the light-transmissive substrate 21 formed by using the transparent glass plate or the transparent polycarbonate or the like. A first magnetic layer 23, a second magnetic layer 24, a third magnetic layer 25, and a fourth magnetic layer 26 are sequentially laminated in a vacuum by, for example, continuous sputtering or the like to form a four-layer magnetic layer. The film is being formed. Further, a second dielectric layer 27 made of a non-magnetic metal film or a dielectric film is formed on the fourth magnetic layer 26, and a UV curable resin or the like is used on the second dielectric layer 27 if necessary. The protective layer 28 is formed. At this time, the irradiation of the laser beam to the second magneto-optical recording medium 20A is performed from the light transmissive substrate 21 side toward the first magnetic layer 23 to the fourth magnetic layer 26.

Here, in the second magneto-optical recording medium 20A, of the first to fourth magnetic layers 23 to 26 having the four-layer structure, the first magnetic layer 23 on the laser beam irradiation side is
Similar to the first magnetic layer 13 formed on the first magneto-optical recording medium 10A described above, a film having a small magnetic anisotropy for facilitating the movement of the domain wall due to the temperature gradient created by the irradiation of the laser beam. And functions as a domain wall displacement layer.

The first magnetic layer 23 is formed as a film having a magnetization easy direction in the vertical direction (direction perpendicular to the film surface), that is, an amorphous thin film made of a heavy rare earth-iron group metal which is a so-called vertical magnetization film. , Gd-Fe film or Gd-Fe
-A material based on a Co film is used. And
Also here, as described later, the film is formed so that it can be handled as a case where the domain wall motion in the first magnetic layer 23 greatly exceeds the Walker's limit. Specifically, in the first magnetic layer 23 Heavy rare earth (Gd) iron group metal (F
e or Fe-Co) element concentration ratio (at.% ratio)
By setting the range of 28.0 ≦ Gd ≦ 29.0,
The film is formed so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is larger than 1. The range of the element concentration ratio will be described later. At this time, the amount of Co added in the first magnetic layer 23 is adjusted, and further, Al or Cr is added.
The Curie temperature Tc11 of the first magnetic layer 23 is adjusted by adding a non-magnetic element such as.

Next, the second and third magnetic layers 24 and 25 are formed in two layers differently from the second magnetic layer 14 formed in the above-mentioned first magneto-optical recording medium 10A. Second, third
By forming the second magnetic layer 24 of the magnetic layers 24 and 25 as an extremely thin film, the second magnetic layer 24 is moved forward in the moving direction of the laser beam in the temperature region (about 430K to about 490K) where the domain wall can move. It has the function of causing only the movement of the domain wall from.

Of the second and third magnetic layers 24 and 25, at least the third magnetic layer 25 is the fourth magnetic layer 2 described later.
When the magnetic domain recorded in 6 is exchange coupled to the first magnetic layer 23 through the second and third magnetic layers 24 and 25, the magnetization disappears due to the temperature rise due to the irradiation of the laser beam during reproduction. Is functioning as. The second and third magnetic layers 24,
25 is also a film having an easy magnetization direction in the vertical direction (direction perpendicular to the film surface), that is, is formed as an amorphous thin film made of a heavy rare earth-iron group metal that serves as a so-called perpendicular magnetization film, and T
A material based on a b-Fe film or a Dy-Fe film is used, and a non-magnetic element such as Al or Cr or Co is added to the Curie temperatures Tc22, T of the second and third magnetic layers 24, 25.
The film is formed while adjusting c23.

Next, the fourth magnetic layer 26, like the third magnetic layer 15 formed on the first magneto-optical recording medium 10A described above, is irradiated by a laser beam during recording and is used for a magnetic head (not shown) or the like. After an information signal is recorded in the form of magnetic domains (magnetization reversal regions) on a film surface having an easy axis of magnetization in the vertical direction by an external magnetic field, it has a sufficient coercive force to stably hold the recorded magnetic domains at room temperature. In addition, the film needs to have a Curie temperature Tc24 suitable for recording an information signal, and functions as a recording layer (memory layer).

The fourth magnetic layer 26 is also formed as an amorphous thin film made of a heavy rare earth-iron group metal, which is a film having a magnetization easy direction in the vertical direction (direction perpendicular to the film surface), that is, a so-called vertical magnetization film. , Tb-Fe-Co film or Dy
A material based on a —Fe—Co film is used.
The Curie temperature Tc24 of the fourth magnetic layer 26 is adjusted by adding a non-magnetic element such as 1 or Cr, and the iron group metal (Fe) of heavy rare earth (Tb or Dy) in the fourth magnetic layer 26 is adjusted.
The element concentration ratio (at.% Ratio) to -Co) is 23.5
The range of ≦ Tb ≦ 25.5 or 25.5 ≦ Dy ≦ 28.5 is set, and the range of the element concentration ratio will be described later.

Then, the first, second, third, and so on are taken into consideration in consideration of the temperature rising state at the time of recording and reproducing by the laser beam with respect to the second magneto-optical recording medium 20A configured as described above.
Curie temperature T of the fourth magnetic layer 23, 24, 25, 26
c21, Tc22, Tc23, Tc24 is about 530
K, about 430K, about 420K, and about 590K are desirable. Here, the Curie temperatures Tc21 and Tc of the first, second, third and fourth magnetic layers 23, 24, 25 and 26, respectively.
c22, Tc23, and Tc24 can increase the Curie temperature by increasing the amount of Co added in each magnetic layer, while Al, Cr, etc. which do not significantly change the magnetic characteristics of each magnetic layer. Since the Curie temperature can be lowered by increasing the addition amount of the non-magnetic element, the addition amount of Co or the non-magnetic element is adjusted for each magnetic layer to adjust the above Curie temperatures Tc21, Tc22, Tc23, T
24 is set so that Tc24>Tc21>Tc22> Tc23.

Further, the first, second, third and fourth magnetic layers 2
Film thickness t21, t22, t2 of 3, 24, 25, 26
3, t24 is about 30 nm, about 5 to 15 nm,
It is desirable to set the thickness to about 10 nm and about 60 to 80 nm.

Here, the first and second aspects of the present invention described above.
In the magneto-optical recording media 10A and 20A, the domain wall movement of the first magnetic layer 13 or the first magnetic layer 23 will be described in detail.

FIG. 3 is a diagram for explaining the domain wall motion of the first magnetic layer (domain wall motion layer) in the first and second magneto-optical recording media according to the present invention.

In the first and second magneto-optical recording media 10A and 20A according to the present invention, as described above, especially, the first magnetic layer 13 or the first magnetic layer 23 is the Gd-Fe film or the Gd-Fe film.
Using a material based on a d-Fe-Co film, Gd
Element ratio of Fe to Fe or Fe-Co (at%)
Ratio) is set in the range of 28.0 ≦ Gd ≦ 29.0, and the third magnetic layer 15 or the fourth magnetic layer 26 is made of Tb-Fe-.
Using a material based on a Co film or a Dy-Fe-Co film, the element concentration ratio (at.% Ratio) of Tb or Dy to Fe-Co is 23.5≤Tb≤25.5 or 25.
By setting 5 ≦ Dy ≦ 28.5, a Wal described later will be obtained.
This can be handled as a case where the limit of ker is greatly exceeded, whereby the domain wall movement is swiftly performed, and the jitter characteristic, which is one of the reproduction signal characteristics, is greatly improved.

The effectiveness of the present invention will be described below by showing the calculation results based on the theory of micromagnetics and the experimental results for verifying the results. The theoretical calculation is performed by the molecular field approximation, but the parameter is determined by actually measuring the temperature characteristics of each magnetic layer shown as an example above and fitting the calculation curve to the value to determine the parameter used for the calculation. ing. The domain wall moving velocity was calculated by solving the Landau-Lifshitz-Gilbert equation of the ferrimagnet for the single domain structure.

Generally, in the magneto-optical recording medium, the domain wall motion of the first magnetic layer (domain wall motion layer) 13 or 23 starts when the relationship of the following expression 1 is established.

[0058]

[Equation 1] In this equation 1, σ _D indicates domain wall energy, and σ _W
Represents the interface domain wall energy due to exchange coupling between the domain wall displacement layer (first magnetic layer) and the recording layer (third magnetic layer or fourth magnetic layer), χ represents the position coordinate in the track direction, M _s ,
H _w and t are the magnetization, domain wall coercive force, and film thickness of the domain wall displacement layer, respectively. Further, the left side in the equation 1 is a driving force for the domain wall movement, the right side in the equation 1 is a force for preventing the domain wall movement, and the left side and the right side in the above equation 1 are separated from each other. In the case shown, the domain wall movement starts from the intersection of the curve characteristic on the left side and the curve characteristic on the right side to the left side (Position 0 side) in the figure.

The characteristic curves shown in FIG. 3 are the results for the first and second magneto-optical recording media 10A and 20A according to the present invention. The horizontal axis shown in FIG. 3 is the position coordinates with the origin of the spot center of the reproducing laser beam as the origin 0 and the traveling direction of the reproducing laser beam as positive, and the vertical axis indicates the driving force of the domain wall movement and the domain wall movement. It shows the power to do.

Here, in order to consider the domain wall moving speed,
Landau-Lifshitz-Gilbert (L
LG) equation must be applied. Domain wall movement is
It is realized by continuous magnetization reversal, but the magnetic moment is
It is obtained as the sum of the orbits of electrons and the magnetism of spins, and because it is accompanied by angular momentum, Lermore's precession motion (= motion in which the axial direction of the magnetic moment changes) occurs in its reversal motion. Therefore, the introduction of the gyromagnetic ratio explained the dynamic magnetization mechanism of the LLG.
An equation is needed. Furthermore, when the drive magnetic field of the domain wall is small, the domain wall moves while maintaining its structure, but when the drive magnetic field of the domain wall increases, the domain wall structure itself moves while changing. In the former (when the domain wall drive magnetic field is small), the domain wall moving speed is almost proportional to the drive magnetic field, but in the latter (when the domain wall driving magnetic field is large), the domain wall moving speed shows a complicated behavior with respect to the drive magnetic field. Walke the border between the former and the latter
Call it the limit of r.

Here, the magneto-optical recording medium 10 according to the present invention.
The domain wall moving velocity V in A and 20 A are both Walke
Since it can be handled as a case where the limit of r is greatly exceeded, it can be obtained by the following equations 2 and 3, and the domain wall moving velocity V obtained by the equation 2 among the equations 2 and 3 is It is the main one.

[0062]

[Equation 2]

[Equation 3] In the above Equations 2 and 3, the domain wall drive magnetic field H is set to the constant 2
π, saturation magnetization M _s, and Gilbert's damping constant α
_eff And the value of the standardized magnetic field h is 1 <h
Or the magnetic domain wall moving speed V is determined depending on whether h <1, and when the standardized magnetic field h becomes larger than 1, the magnetic domain wall moving speed V obtained by the equation 2 is mainly the magneto-optical characteristic according to the present invention. It is considered to be the domain wall moving speed in the recording media 10A and 20A.

The phenomenon above the Walker's limit and the phenomenon below it are due to the difference in the temperature characteristics of the magnetization of the domain wall displacement layer. Due to the characteristic difference, the actual domain wall displacement is The normalized magnetic field is realized when 1 <h, and in the latter case, the normalized magnetic field is realized when h <1.

Here, Gilbert's damping constant α _eff Is the Landau-Lifshitz loss constant λ _eff. Can be expressed by the following equation 4.

[0065]

[Equation 4] In this approximation calculation, λ _eff / Γ _eff = About 10 (emu / cm ³ ). Further, the domain wall drive magnetic field H is expressed by the following equation 5 in the domain wall moving layer having a small domain wall coercive force.

[0066]

[Equation 5] Therefore, under the effective anisotropy constant K >> 2πM _s ² ,
From these equations 4 and 5, the above equation 2 can be transformed as shown in equation 6.

[0067]

[Equation 6] From Equation 6 above, the saturation magnetization M _s is reduced to make Walk
It can be seen that when the domain wall is moved by a magnetic field much larger than the limit of er, the domain wall moving speed becomes highest at the saturation magnetization M _s = 0. This feature is, in other words, the saturation magnetization M _s
When it deviates from = 0, it means that the domain wall moving speed becomes slow. Therefore, since the saturation magnetization in the temperature range where the domain wall motion is realized largely depends on the heavy rare earth element content of the domain wall motion layer which is a ferrimagnetic material, in order to realize good domain wall motion, It is necessary to strictly control the composition of the heavy rare earth (Gd) element.
Therefore, from the calculation result of the domain wall motion velocity, the time until the domain wall motion is completed was calculated, and the composition dependence of the domain wall motion layer was examined.

FIG. 4 is a diagram in which the change in the domain wall moving speed and the change in the domain wall position in the first magnetic layer (domain wall moving layer) in the magneto-optical recording medium according to the present invention are plotted against time. In FIG. 4, the position on the vertical axis is the position coordinate in the track direction with the origin of the spot of the reproduction laser beam as the origin 0 and the traveling direction of the reproduction laser beam as the positive direction. Here, the element concentration ratio of the heavy rare earth (Gd) contained in the first magnetic layer 13 or the first magnetic layer 23 serving as the domain wall displacement layer to the iron group metal (Fe or Fe—Co) is 28.5.
at. %. The domain wall movement for magnifying and reproducing the magnetic domain (record mark) can be completed slightly behind the center of the reproduction laser beam (with the beam traveling direction as the front).
You can see from this result. Then, when the domain wall movement stops halfway or a long time is required to complete it, the signal quality of the domain wall movement reproduction is impaired.

FIG. 5 shows, in the magneto-optical recording medium according to the present invention, near the center of the reproducing laser beam (-0.05 μm,
The figure which showed the result of having plotted the change of the time required for a moving magnetic domain wall to reach 0.00 micrometer, +0.05 micrometer) with respect to the composition of heavy rare earth (Gd) in a 1st magnetic layer (domain wall moving layer). Is.

As shown in FIG. 5, the first magnetic domain wall displacement layer is formed.
It can be seen that the time required for the completion of the domain wall movement in the magnetic layer 13 or the first magnetic layer 23 varies greatly with the change in the composition of the heavy rare earth (Gd). From this result, the element concentration ratio (at.% Ratio) of the heavy rare earth (Gd) to the iron group metal (Fe—Co) in the first magnetic layer 13 or the first magnetic layer 23, which is the domain wall displacement layer, is 28. It can be said that it is desirable that the range is 0 ≦ Gd ≦ 29.0.

On the other hand, the magneto-optical recording medium 10 according to the present invention.
As described above, in the domain wall movement in the domain wall drive magnetic field that greatly exceeds the Walker's limit, such as A and 20A, as the domain wall drive magnetic field increases, a complicated behavior is exhibited. Therefore, in order to smoothly move the domain wall, it is necessary to take into consideration the stray magnetic field that hinders the movement. In the vicinity of the domain wall movement start position, the region in the traveling direction of the domain wall is at a high temperature, and the domain wall movement region has a smaller magnetization than the other regions, so that the stray magnetic field in the expanding domain region is large. Since the magnetostatic energy becomes smaller and becomes stable when the domain wall is formed in a place where the magnetization is large, the stray magnetic field has an effect of hindering the domain wall movement. On the other hand,
In the vicinity of the domain wall movement completion position, the magnitude of the repulsive force from the domain domain wall of the previous signal increases in proportion to the stray magnetic field, so the domain wall movement range is limited when the stray magnetic field is large, and the S / N decreases. In the case of the present invention, the composition of the heavy rare earth (Gd) element in the first magnetic layer 13 or the first magnetic layer 23 which becomes the domain wall motion layer is within the above range, and the temperature region where the domain wall motion occurs (about 430K to Since the saturation magnetization of the domain wall motion layer at about 490 K) is extremely small, it is considered that there is almost no influence of the stray magnetic field from the domain wall motion layer, but from the third magnetic layer 15 or the fourth magnetic layer 26 which is the recording layer. It is necessary to consider the effect of stray magnetic fields.

Therefore, in the first and second magneto-optical recording media 10A and 20A according to the present invention, in order to solve this problem,
The improvement of the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer was examined as follows.

The third magnetic layer 15 or the fourth magnetic layer 26 in the first and second magneto-optical recording media 10A and 20A according to the present invention will be described below with reference to FIGS. 6 to 10.

FIG. 6 shows the heavy rare earth (Tb) iron group metal (Fe—Co) contained in the third magnetic layer 15 or the fourth magnetic layer 26 in the first and second magneto-optical recording media according to the present invention. The element concentration ratio is 27.5 at. FIG. 7 is a diagram showing a change in stray magnetic field in the case of%, FIG. 7 shows the third magnetic layer 15 or the fourth magnetic layer 26 in the first and second magneto-optical recording media according to the present invention.
Heavy rare earth (Tb) iron group metal (Fe-Co) contained in
Element concentration ratio to 26.5 at. FIG. 8 is a diagram showing a change in stray magnetic field in the case of%, FIG. 8 is a heavy rare earth element (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 in the first and second magneto-optical recording media according to the present invention. Iron group metal (Fe-C
The element concentration ratio to o) is 25.5 at. FIG. 9 is a diagram showing the change of the stray magnetic field in the case of%, FIG. 9 is a heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 in the first and second magneto-optical recording media according to the present invention. Iron group metal (Fe
-Co) has an element concentration ratio of 24.5 at. FIG. 10 is a diagram showing a change in stray magnetic field in the case of%, and FIG. 10 shows heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 in the first and second magneto-optical recording media according to the present invention. Element concentration ratio to the iron group metal (Fe—Co) of 23.5 at. %
It is a figure showing the change of the stray magnetic field in case of.

First and second magneto-optical recording media 1 according to the present invention
At 0 A and 20 A, the third magnetic layer 15 is changed with respect to the composition change of the third magnetic layer 15 or the fourth magnetic layer 26 which becomes the recording layer.
Alternatively, a stray magnetic field from the fourth magnetic layer 26 (Stray fi
Eld) is examined and the results are shown in FIG.
~ Is shown in FIG. In FIGS. 6 to 10, the third magnetic layer 15 or the fourth magnetic layer 26 serving as a recording layer is Tb-Fe-
This is an example of the case where a Co film is formed, and the position on the horizontal axis is position coordinates in the track direction with the origin of the spot of the reproduction laser beam as the origin 0 and the traveling direction of the laser beam as positive. At this time, the position on the horizontal axis indirectly indicates the temperature change due to the Gaussian distribution of the reproduction laser beam.

In addition, in FIGS.
Saturat of the third magnetic layer 15 or the fourth magnetic layer 26 that generates the stray magnetic field together with the field (stray magnetic field)
IonMagnification (saturation magnetization) is also shown for reference. It should be noted that the Trace field
d and Saturation Magnetizati
The vertical axes indicating on respectively indicate magnetization in one direction if the + direction is upward magnetization, and
Only the scale unit of the ratio Magnification in FIG. 10 is double that in FIGS. 6 to 9.

Here, the domain wall of the minute recording mark recorded on the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer is
Since it moves toward the previous recording mark, the third magnetic layer 15 or the fourth magnetic layer 26 to be a recording layer.
When a random modulation signal is recorded in, the repulsive force from the domain wall of the recording mark immediately before that must be taken into consideration. Therefore, the study here considers the case where a domain wall exists in the third magnetic layer 15 or the fourth magnetic layer 26 immediately below the center of the reproduction laser beam (the origin position of the position coordinate in the track direction). The results shown in FIG. 6 to FIG.
Heavy rare earth (T) contained in the magnetic layer 15 or the fourth magnetic layer 26.
The element concentration ratio of b) to the iron group metal (Fe—Co) is
27.5 at. %, 26.5 at. %, 25.5a
t. %, 24.5 at. %, 23.5 at. % Corresponds to each case. As can be seen from FIGS. 6 to 10, although the stray magnetic field at the domain wall movement start position decreases as the element concentration ratio decreases, the stray magnetic field near the origin, which is the final arrival point of the domain wall, increases.

Next, FIG. 11 is a diagram showing a magnetic domain wall driving magnetic field with respect to position coordinates in the track direction in the magneto-optical recording medium according to the present invention. FIG. 12 is a recording layer in the magneto-optical recording medium according to the present invention. It is the figure which showed the result of having measured the standardized Jitter when changing the element concentration ratio of the heavy rare earth (Tb) contained in the 3rd magnetic layer or the 4th magnetic layer with respect to the iron group metal (Fe-Co).

As shown in FIG. 11, the domain wall drive magnetic field is
The position is relatively small at the domain wall movement start position in the vicinity of 0.3 μm, and rapidly increases from the domain wall movement start position to the maximum temperature position (final reaching point of the moving domain wall). Therefore, it is important to consider the influence of the stray magnetic field at the movement start position. As shown in FIGS. 6 to 10, the stray magnetic field at the movement start position of the domain wall causes the heavy rare earth (Tb) iron group metal (Fe) contained in the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer. The element concentration ratio with respect to —Co) decreases as it decreases. On the other hand, the stray magnetic field at the maximum temperature position, on the contrary, suddenly increases. In the present invention, the first magnetic layer 13 or the first magnetic layer 23 serving as the domain wall displacement layer has a domain wall displacement temperature region (about 43 mm).
Since the magnetization of the heavy rare earth sublattice is predominant in the range of 0 K to about 490 K), when the stray magnetic field from the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer is negative, the stray magnetic field is the domain wall motion layer. It works in the direction of helping the domain wall movement. 9 and 1
In the case of 0, when the domain wall displacement layer slightly moves, the stray magnetic field from the recording layer changes to a direction that assists the domain wall displacement. However, immediately before the highest temperature position, the stray magnetic field changes to a direction in which domain wall movement is hindered and rapidly increases. Therefore, it is not preferable to further reduce the composition of the heavy rare earth (Tb), considering that the moving domain wall exhibits complicated behavior while the domain wall structure itself changes when the domain wall driving magnetic field increases. And, the case of FIG. 10 is considered to be a desirable state.

In order to verify the above results, the element concentration of the heavy rare earth (Gd) contained in the first magnetic layer 13 or the first magnetic layer 23 serving as the domain wall displacement layer with respect to the iron group metal (Fe or Fe-Co). The ratio is 28.5 at. % When the element concentration ratio of the heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer to the iron group metal (Fe—Co) is changed. FIG. 12 shows the results of measuring and comparing the modified Jitter. Here, the modulation signal having the shortest mark length of 0.08 μm was recorded, and the domain wall movement reproduction was evaluated. The element concentration ratio of the heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer to the iron group metal (Fe—Co) is 24.5 at.
%, The best jitter value is shown, and the jitter characteristics tend to deteriorate when the composition of heavy rare earth (Tb) increases or decreases. This result supports the above-mentioned consideration result of the stray magnetic field, whereby the element concentration ratio of the heavy rare earth (Tb) in the third magnetic layer 15 or the fourth magnetic layer 26 to the iron group metal (Fe—Co). (At.% Ratio)
Can be said to be in the range of 23.5 ≦ Tb ≦ 25.5.

Each of the characteristics shown in FIGS. 6 to 10 and FIG. 12 is the case where a Tb-Fe-Co film is formed on the third magnetic layer 15 or the fourth magnetic layer 26 serving as a recording layer. However, when the Dy-Fe-Co film was formed on the third magnetic layer 15 or the fourth magnetic layer 26, the same examination as above was performed.
When a Dy-Fe-Co film is used for the magnetic layer 15 or the fourth magnetic layer 26, the element concentration ratio of Dy to Fe-Co (a
t. It has been found that the (% ratio) is preferably in the range of 25.5 ≦ Dy ≦ 28.5.

Within the above composition range, a combination of the first magnetic layer 13 and the third magnetic layer 15 in the magneto-optical recording medium 10A, or a combination of the first magnetic layer 23 and the first magnetic layer 23 in the magneto-optical recording medium 20A is used. In combination with the four magnetic layers 26, the magneto-optical recording media 10A and 20A according to the present invention, which have a high magnetic domain wall movement speed, reduce the influence from the stray magnetic field, and are one of the reproduction signal characteristics. A certain jitter characteristic will be greatly improved.

Next, it is possible to reduce the stray magnetic field leaking from the third magnetic layer 15 or the fourth magnetic layer 26 serving as the recording layer to the first magnetic layer 13 or the first magnetic layer 23 serving as the domain wall motion layer, and
At the same time, another improvement example capable of improving the recording magnetic field sensitivity will be described with reference to FIGS.

FIG. 13 is a sectional view schematically showing the layer structure of Modification 1 in which the first magneto-optical recording medium according to the present invention is partially modified, and FIG. 14 is the second magneto-optical recording medium according to the present invention. FIG. 15 is a cross-sectional view schematically showing the layer structure of Modification 2 in which the recording medium is partially modified, and FIG. 15 is a magneto-optical recording medium of Modification 1 (or Modification 2).
In the magneto-optical recording medium), when the third magnetic layer (or the fourth magnetic layer) is formed of a two-layer film including a Tb-Fe-Co film and a Gd-Fe-Co film, the magnetization of the two-layer film FIG. 16 is a diagram schematically showing an anti-parallel coupling that becomes stable when the directions are opposite to each other. FIG. 16 shows the third magnetic layer in the magneto-optical recording medium of Modified Example 1 (or the magneto-optical recording medium of Modified Example 2). (Or the fourth magnetic layer) is a Tb-Fe-Co film and a Gd-Fe-C film.
In the case of forming a two-layer film composed of an o film and a two-layer film, it becomes stable when the magnetization directions of the two-layer film are the same as each other.
-Rich) parallel coupling diagram, FIG.
In the magneto-optical recording medium of Modified Example 1 (or the magneto-optical recording medium of Modified Example 2), 7 is a third magnetic layer (or a fourth magnetic layer) made of a Tb-Fe-Co film and a Gd-Fe-Co film. FIG. 18 is a diagram schematically showing an iron group dominant (TM-rich) parallel coupling that becomes stable when the magnetization directions of the two-layer film are the same when the two-layer film is formed. In the magneto-optical recording medium of No. 1 (or the magneto-optical recording medium of Modified Example 2), the third magnetic layer (or the fourth magnetic layer) is made of Tb-Fe-Co.
FIG. 19 is a characteristic diagram of the two-layer film that always maintains antiparallel coupling from room temperature to the Curie temperature when the two-layer film including the film and the Gd-Fe-Co film is formed. FIG. Alternatively, in the magneto-optical recording medium of Modification 2, the third
The magnetic layer (or fourth magnetic layer) is composed of a Tb-Fe-Co film and a Gd.
When a two-layer film including a -Fe-Co film is formed, room temperature to about 385K (compensation temperature of a) is parallel-coupled to the RE-rich film, and about 385K to about 530K (compensation temperature of b) FIG. 20 is a characteristic diagram of a two-layer film which is an anti-parallel coupling, which is a parallel coupling of the TM-rich film from about 530 K to the Curie temperature, and FIG. , Tb-F
FIG. 9 is a diagram showing a result of reducing the recording magnetic field of the third magnetic layer (or the fourth magnetic layer) by the e-Co film and the Gd-Fe-Co film.

First, as shown in FIG. 13, a magneto-optical recording medium 10B according to Modification 1 in which the first magneto-optical recording medium according to the present invention is partially modified, is the same as the magneto-optical recording medium 10B described above with reference to FIG. The third magnetic layer 15 is different from the first magneto-optical recording medium 10A only in the film forming method, and other configurations are the same. 15 is a Tb-Fe-Co film 15a and Gd-Fe-Co.
The third magnetic layer 15 is a ferrimagnetic perpendicular magnetization film made of a heavy rare earth-iron group metal because it is formed as a two-layer film including the film 15b. At this time, Tb-Fe-Co
In the third magnetic layer 15 including the film 15a and the Gd-Fe-Co film 15b, Tb-Fe-C having a large magnetic anisotropy.
It is desirable to form the film 15a side on the laser beam irradiation side, and accordingly, the Gd-Fe-Co film 15b is laminated on the Tb-Fe-Co film 15a.

Next, as shown in FIG. 14, a magneto-optical recording medium 20B according to Modification 2 in which the second magneto-optical recording medium according to the present invention is partially modified has also been described with reference to FIG. The film forming method of the fourth magnetic layer 26 is different from that of the second magneto-optical recording medium 20A, and the other configurations are the same. Therefore, only different points will be described. The layer 26 is a Tb-Fe-Co film 26a and a Gd-Fe-Co film.
The fourth magnetic layer 26 is a two-layer film including the film 26b, and thus the fourth magnetic layer 26 is a ferrimagnetic perpendicular magnetization film made of a heavy rare earth-iron group metal. At this time, Tb-Fe-Co
In the fourth magnetic layer 26 composed of the film 26a and the Gd-Fe-Co film 26b, Tb-Fe-C having a large magnetic anisotropy.
It is desirable to form the o film 26a side on the laser beam irradiation side, and accordingly, the Gd-Fe-Co film 26b is laminated on the Tb-Fe-Co film 26a.

Here, as shown in FIGS.
b-Fe-Co film 15a (or 26a) and Gd-Fe-
Third magnetic layer 15 including Co film 15b (or 26b)
In (or the fourth magnetic layer 26), the arrow without a circle indicates the magnetic moment of the iron group sublattice, the arrow with a circle indicates the magnetic moment of the rare earth sublattice, and The length of the arrow indicating the moment indicates the magnitude of each sublattice magnetization. Further, a large hollow arrow including the arrows of the rare earth sublattice and the iron group sublattice indicates the direction of magnetization. At this time, rare earth metal (Rare Ear)
th Metal) is a transition metal of the iron group (Trans
in which the transition metal of the iron group is more predominant than the rare earth metal is referred to as the iron group predominance (TM-rich). is doing.

The Tb-Fe-Co film 15a (or 26a) and the Gd-Fe-Co film 15b (or 26b) in the third magnetic layer 15 (or the fourth magnetic layer 26) are shown in FIG. The anti-parallel coupling in which the magnetization directions of the bilayer film are opposite to each other and stable when in the antiparallel state, or, as shown in FIG. 16, the bilayer film has the same magnetization direction and the parallel state. Rare earth dominance (RE-ric
h) parallel coupling, or, as shown in FIG. 17, the iron group-dominant (TE-rich) parallel coupling in which the magnetization directions of the two-layer film are stable in the same direction and in the parallel state. , Which can be taken according to the conditions shown in FIG. 18 or FIG. 19 described below.

That is, as shown in FIG. 18, the third magnetic layer 1
5 (or the fourth magnetic layer 26), a is a Tb-Fe-Co film 15 in which a is iron group dominant (TE-rich).
a (or 26a) temperature characteristics, and b is a rare earth dominant (RE-rich) Gd-Fe-Co film 15
The temperature characteristic of b (or 26b) is shown. And both films 15a and 15b (or 26a and 26b) are 300K
From room temperature near the Tb-Fe-Co film 15a (or 26
Up to the Curie temperature of a), the double-layer film always maintains the antiparallel coupling as shown in FIG.

Here, when the two-layer film of the third magnetic layer 15 (or the fourth magnetic layer 26) maintains anti-parallel coupling, Tb-Fe-C which is iron group dominant (TE-rich).
o Temperature characteristic a of the film 15a (or 26a) and Gd-Fe-Co film 15b which is a rare earth dominant (RE-rich) film.
By calculating the difference c = ab between the temperature characteristic b of (or 26b) and the temperature characteristic b, the apparent temperature characteristic c of the magnetization can be obtained.

Then, the temperature region for reproducing by the domain wall motion in the first magnetic layer 13 (or 23), that is, about 430.
From K to about 490 K, since the two-layer film of the third magnetic layer 15 (or the fourth magnetic layer 26) has anti-parallel coupling,
It is clear from the drawing that the apparent magnetization described above is suppressed to a small value of about 20 emu / cm ³ or less. At this time, Tb-Fe- which is an iron group dominant (TE-rich)
Co film 15a (or 26a) and rare earth predominant (RE-r
ich) Gd-Fe-Co film 15b (or 26)
b) means that the exchange coupling force, which is a microscopic interaction between atoms, acts, whereas the third magnetic layer 15 serving as a recording layer.
The force due to the stray magnetic field leaking from (or the fourth magnetic layer 26) to the first magnetic layer 13 (or 23) serving as the domain wall displacement layer is a magnetostatic macroscopic force. Stray magnetic field of each film 15a, 15b (or 26
It is understood that the magnetization directions of a and 26b) are opposite to each other and can be reduced by reducing the difference between the magnetizations, that is, by reducing the apparent magnetization. Therefore,
In the temperature region (about 430K to about 490K) in which reproduction is performed by moving the domain wall in the first magnetic layer 13 (or 23), the direction of magnetization of the bilayer film of the third magnetic layer 15 (or the fourth magnetic layer 26). By maintaining the anti-parallel coupling which becomes stable when the two are opposite to each other, it is possible to reduce the stray magnetic field leaking from the recording layer to the domain wall displacement layer.

Next, for the two-layer film of the third magnetic layer 15 (or the fourth magnetic layer 26) shown in FIG. 18, Tb-Fe-C was used.
o The amount of Tb in the film 15a (or 26a) is increased, and Gd in the Gd-Fe-Co film 15b (or 26b) is increased.
When the amount of is reduced, a two-layer film of the third magnetic layer 15 (or the fourth magnetic layer 26) having the characteristics shown in FIG. 19 is obtained.
In FIG. 19, a indicates the temperature characteristics of the Tb-Fe-Co film 15a (or 26a), and b indicates Gd-Fe-C.
The temperature characteristics of the o film 15b (or 26b) are shown. Further, c indicates the apparent temperature characteristic of magnetization due to the temperature characteristic a of the Tb-Fe-Co film 15a (or 26a) and the temperature characteristic b of the Gd-Fe-Co film 15b (or 26b).

In the example shown in FIG. 19, the Tb-Fe-Co film 1 of the third magnetic layer 15 (or the fourth magnetic layer 26) is used.
5a (or 26a) has a compensation temperature at which the coercive force is maximized and the sublattice magnetizations of the rare earth and the iron group are approximately equal to each other in the vicinity of 385K, while the Gd-Fe-Co film 15b (or 26a).
In the case of b), there is a compensation temperature in the vicinity of about 530 K at which the coercive force becomes maximum and the sublattice magnetizations of the rare earth and the iron group become substantially equal. At each compensation temperature described above, the direction of magnetization determined by the magnitude relationship of the sublattice magnetizations of the rare earth metal and the iron group metal is reversed at the compensation temperature.

More specifically, in the third magnetic layer 15 (or the fourth magnetic layer 26), from room temperature near 300K to about 3K.
R up to 85 K (compensation temperature of a) as shown in FIG.
This is a parallel combination of E-rich films, and this RE-ri
Temperature characteristic of apparent magnetization when the ch films are coupled in parallel c
Is a value obtained by adding the temperature characteristic a of the Tb-Fe-Co film 15a (or 26a) and the temperature characteristic b of the Gd-Fe-Co film 15b (or 26b). Also, from about 385K to about 5
Up to 30 K (b compensation temperature), the anti-parallel coupling as shown in FIG. 15 is obtained, and the apparent temperature characteristic c of the magnetization at this anti-parallel coupling is Tb-Fe-Co film 15.
a (or 26a) temperature characteristic a and Gd-Fe-Co film 1
The difference value with the temperature characteristic b of 5b (or 26b) is taken. Further, from about 530K, the Tb-Fe-Co film 15a (or 2
Up to the Curie temperature of 6a) TM as shown in FIG.
-Rich film is in parallel connection state, and this TM-r
The apparent temperature characteristic c of the magnetization in the parallel coupled state of the ich film is obtained by adding the temperature characteristic a of the Tb-Fe-Co film 15a (or 26a) and the temperature characteristic b of the Gd-Fe-Co film 15b (or 26b). Take the value you did. In other words, at room temperature, the RE-rich film shown in FIG. 16 is connected in parallel, at the reproducing temperature, the anti-parallel film shown in FIG. 15 is formed, and at the recording temperature, the TE-rich film shown in FIG. 17 is formed in parallel.

Also in the example shown in FIG. 19, the first
In the temperature range in which reproduction is performed by moving the magnetic domain wall in the magnetic layer 13 (or 23), that is, in the range of about 430K to about 490K, the two-layer film of the third magnetic layer 15 (or the fourth magnetic layer 26) is an anti-parallel coupling. In addition, it is apparent from the drawing that the above-mentioned apparent magnetization is suppressed to a small value of about 20 emu / cm ³ or less. Therefore, in the temperature region (about 430K to about 490K) in which reproduction is performed by moving the domain wall in the first magnetic layer 13 (or 23), the third magnetic layer 15 (or the fourth magnetic layer 15).
By maintaining the anti-parallel coupling which becomes stable when the directions of magnetization of the two-layer film of the magnetic layer 26) are opposite to each other,
It is possible to reduce the stray magnetic field leaking from the recording layer to the domain wall displacement layer.

Here, as the third magnetic layer 15 (or the fourth magnetic layer 26) serving as the recording layer, the Tb-Fe-Co film 15a is formed.
(Or 26a) and the Gd-Fe-Co film 15b (or 26
By using the two-layer film according to (b), it is possible to simultaneously realize the reduction of the recording magnetic field as shown in FIG. That is, FIG. 20 shows the result of examination of the recording magnetic field sensitivity by the optical modulation recording. C / N rising negative magnetic field absolute value and C / N
The magnitude of the positive magnetic field with which N is saturated is further reduced, whereby the magnetic field sensitivity is improved. In the case of the optical modulation recording described above, generally, when a weak direct current external magnetic field is applied in the recording direction and a laser beam is applied to this to apply heat depending on the presence or absence of a signal, the coercive force drops. , The magnetization is reversed in the direction of the external magnetic field.
Information of 1 "and" 0 "is recorded.

From the result of FIG. 20, the third magnetic layer 1
5 (or the fourth magnetic layer 26), the recording magnetic field sensitivity of the anti-parallel exchange coupling bilayer film is significantly reduced to about 60 Oe. Usually, Tb-F used as a recording layer
Compared with the e-Co film 15a (or 26a), the anti-parallel exchange coupled Gd-Fe-Co film 15b (or 26) is used.
In b), since the perpendicular magnetic anisotropy is small and the coercive force at a temperature deviating from the compensation temperature is extremely small, recording can be performed with a small external magnetic field, and the recorded magnetic domain is Tb-Fe-Co due to exchange coupling. It follows a recording mechanism of being transferred to the film 15a (or 26a) and being stably stored. It is considered that this improves the recording magnetic field sensitivity.

[0098]

In the magneto-optical recording medium according to the present invention described in detail above, according to claim 1, when the magnetic layers are laminated in a three-layer structure, especially the first magnetic layer to be the domain wall displacement layer is Gd-Fe film or Gd so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is greater than 1.
-Fe-Co film is formed from a material based on
Element concentration ratio of Fe to Fe or Fe-Co (at%)
Ratio) is set in the range of 28.0 ≦ Gd ≦ 29.0, and the third magnetic layer serving as a recording layer is a Tb-Fe-Co film or a Dy- film.
The Fe-Co film is used as a base material, and Tb is used.
Or the element concentration ratio of Dy to Fe-Co (at.%
Ratio) to 23.5 ≦ Tb ≦ 25.5 or 25.5 ≦ Dy ≦
Since the Curie temperatures Tc11, Tc12, and Tc13 of the first, second, and third magnetic layers are set to Tc13>Tc11> Tc12 while being set to the range of 28.5, when the laser beam is irradiated during reproduction. The domain wall movement that occurs in the first magnetic layer becomes rapid, the jitter characteristic, which is one of the reproduction signal characteristics, can be significantly improved, and a higher density magneto-optical recording medium can be provided.

According to the second aspect, the magnetic layer is formed of 4
When laminated in a layered structure, the first magnetic layer, which will be the domain wall displacement layer, in particular, has a Gd-Fe film or a Gd-Fe film so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is greater than 1. -Co film is used as a base material, and the element concentration ratio of Gd to Fe or Fe-Co (a
t. % Ratio) is set within a range of 28.0 ≦ Gd ≦ 29.0, and the fourth magnetic layer serving as a recording layer is formed of a material based on a Tb-Fe-Co film or a Dy-Fe-Co film. And the element concentration ratio of Tb or Dy to Fe-Co (a
t. % Ratio) of 23.5 ≦ Tb ≦ 25.5 or 25.5 ≦
Dy ≦ 28.5 is set, and the first, second, and
Curie temperatures Tc21 and Tc2 of the third and fourth magnetic layers
2, Tc23 and Tc24 are Tc24>Tc21> Tc2
Since 2> Tc23 is set, when the laser beam is irradiated during reproduction, only the domain wall moves from the front in the moving direction of the laser beam in the temperature region where the domain wall can move in the first magnetic layer. It is possible to further greatly improve the jitter characteristic, which is one of the above, and to provide a higher density magneto-optical recording medium.

According to a third aspect of the present invention, the magnetic layer comprises three layers.
When laminated in a layered structure, the first magnetic layer, which will be the domain wall displacement layer, in particular, has a Gd-Fe film or a Gd-Fe film so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is greater than 1. -Co film is used as a base material, and the element concentration ratio of Gd to Fe or Fe-Co (a
t. % Ratio) is set in the range of 28.0 ≦ Gd ≦ 29.0, and the third magnetic layer serving as a recording layer is formed of a two-layer film including a Tb-Fe-Co film and a Gd-Fe-Co film. In addition, since the anti-parallel coupling, which becomes stable when the magnetization directions of the two-layer film are opposite to each other, is maintained in the temperature region where reproduction is performed by moving the domain wall in the first magnetic layer, the recording layer and By reducing the stray magnetic field leaking from the third magnetic layer to the first magnetic layer, which is the domain wall displacement layer, it is possible to further improve the reproduction signal characteristic, that is, the jitter characteristic, and at the same time, improve the recording magnetic field sensitivity. It is possible to provide a higher density magneto-optical recording medium.

Further, according to the fourth aspect, the magnetic layer is formed into four layers.
When laminated in a layered structure, the first magnetic layer, which will be the domain wall displacement layer, in particular, has a Gd-Fe film or a Gd-Fe film so that the normalized magnetic field obtained by normalizing the domain wall drive magnetic field based on the saturation magnetization is greater than 1. -Co film is used as a base material, and the element concentration ratio of Gd to Fe or Fe-Co (a
t. % Ratio) within a range of 28.0 ≦ Gd ≦ 29.0, and the fourth magnetic layer serving as a recording layer is a two-layer film formed of a Tb-Fe-Co film and a Gd-Fe-Co film. In addition, since the anti-parallel coupling, which becomes stable when the magnetization directions of the two-layer film are opposite to each other, is maintained in the temperature region where reproduction is performed by moving the domain wall in the first magnetic layer, the recording layer and By reducing the stray magnetic field leaking from the fourth magnetic layer to the first magnetic layer, which is the domain wall displacement layer, it is possible to further improve the reproduction signal characteristic, that is, the jitter characteristic, and at the same time, improve the recording magnetic field sensitivity. It is possible to provide a higher density magneto-optical recording medium.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a layer structure of a first magneto-optical recording medium according to the present invention.

FIG. 2 is a sectional view schematically showing the layer structure of a second magneto-optical recording medium according to the present invention.

FIG. 3 is a diagram for explaining domain wall motion of the first magnetic layer (domain wall motion layer) in the first and second magneto-optical recording media according to the present invention.

FIG. 4 is a diagram plotting a change in domain wall moving speed and a change in domain wall position in the first magnetic layer (domain wall moving layer) with respect to time in the magneto-optical recording medium according to the present invention.

FIG. 5 shows the magneto-optical recording medium according to the present invention, in the vicinity of the center of the reproducing laser beam (−0.05 μm, 0.00 μm).
(m, +0.05 μm) is a diagram showing a result of plotting a change in time required for the moving domain wall to reach the composition of heavy rare earth (Gd) in the first magnetic layer (domain wall moving layer). ..

6 is an element concentration of heavy rare earth (Tb) contained in a third magnetic layer 15 or a fourth magnetic layer 26 with respect to an iron group metal (Fe—Co) in the first and second magneto-optical recording media according to the present invention. FIG. The ratio is 27.5 at. It is the figure which showed the change of the stray magnetic field in the case of%.

FIG. 7 is an element concentration of the heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 with respect to the iron group metal (Fe—Co) in the first and second magneto-optical recording media according to the present invention. The ratio is 26.5 at. It is the figure which showed the change of the stray magnetic field in the case of%.

FIG. 8 is an element concentration of the heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 with respect to the iron group metal (Fe—Co) in the first and second magneto-optical recording media according to the present invention. The ratio is 25.5 at. It is the figure which showed the change of the stray magnetic field in the case of%.

FIG. 9 is an element concentration of the heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 with respect to the iron group metal (Fe—Co) in the first and second magneto-optical recording media according to the present invention. The ratio is 24.5 at. It is the figure which showed the change of the stray magnetic field in the case of%.

FIG. 10 is an element concentration of the heavy rare earth (Tb) contained in the third magnetic layer 15 or the fourth magnetic layer 26 with respect to the iron group metal (Fe—Co) in the first and second magneto-optical recording media according to the present invention. The ratio is 23.5 at. It is the figure which showed the change of the stray magnetic field in the case of%.

FIG. 11 is a diagram showing a domain wall drive magnetic field with respect to position coordinates in the track direction in the magneto-optical recording medium according to the present invention.

FIG. 12 shows an element concentration ratio of heavy rare earth (Tb) contained in a third magnetic layer or a fourth magnetic layer, which is a recording layer, to an iron group metal (Fe—Co) in a magneto-optical recording medium according to the present invention. It is a figure showing the result of having measured standardized Jitter when changing.

FIG. 13 is a cross-sectional view schematically showing the layer structure of Modification 1 in which the first magneto-optical recording medium according to the present invention is partially modified.

FIG. 14 is a cross-sectional view schematically showing the layer structure of Modification 2 in which the second magneto-optical recording medium according to the present invention is partially modified.

FIG. 15 is a magneto-optical recording medium of Modified Example 1 (or a magneto-optical recording medium of Modified Example 2) in which the third magnetic layer (or the fourth magnetic layer) is a Tb-Fe-Co film and a Gd-Fe-Co film. FIG. 7 is a diagram schematically showing an antiparallel coupling that is stable when the magnetization directions of the two-layer film are opposite to each other when the two-layer film of FIG.

16 is a magneto-optical recording medium of Modified Example 1 (or a magneto-optical recording medium of Modified Example 2) in which a third magnetic layer (or a fourth magnetic layer) is a Tb-Fe-Co film and a Gd-Fe-Co film. In the case of forming a two-layer film by the method, the rare-earth dominance (RE-ric) is stable when the magnetization directions of the two-layer film are the same.
It is the figure which showed the parallel coupling of h) typically.

FIG. 17 is a magneto-optical recording medium of Modified Example 1 (or a magneto-optical recording medium of Modified Example 2) in which the third magnetic layer (or the fourth magnetic layer) is a Tb-Fe-Co film and a Gd-Fe-Co film. Iron group dominance (TM-rich), which is stable when the magnetization directions of the two-layer film are the same when the two-layer film is formed by
It is the figure which showed typically the parallel coupling of.

FIG. 18 is a magneto-optical recording medium of Modified Example 1 (or a magneto-optical recording medium of Modified Example 2) in which a third magnetic layer (or a fourth magnetic layer) is a Tb-Fe-Co film and a Gd-Fe-Co film. FIG. 6 is a characteristic diagram of a two-layer film in which antiparallel coupling is always maintained from room temperature to the Curie temperature when the two-layer film according to and is formed.

FIG. 19 is a magneto-optical recording medium of Modified Example 1 (or a magneto-optical recording medium of Modified Example 2) in which a third magnetic layer (or a fourth magnetic layer) is a Tb-Fe-Co film and a Gd-Fe-Co film. When a two-layer film is formed by, the room temperature to about 385K (compensation temperature of a) is parallel coupling of the RE-rich film, about 3
Anti-parallel coupling from 85K to about 530K (b compensation temperature), TM- from about 530K to Curie temperature
FIG. 10 is a characteristic diagram of a two-layer film that is a parallel combination of rich films.

FIG. 20 is a magneto-optical recording medium of Modified Example 1 (or a magneto-optical recording medium of Modified Example 2), in which a Tb-Fe-Co film and a Gd are used.
-Fe-Co film and third magnetic layer (or fourth magnetic layer)
It is a figure showing the reduction result of the recording magnetic field of.

FIG. 21 is a diagram for explaining an example of a conventional magneto-optical recording medium.

FIG. 22 is a diagram for explaining another example of the conventional magneto-optical recording medium.

[Explanation of symbols]

10A ... First magneto-optical recording medium, 10B ... Magneto-optical recording medium obtained by partially modifying the first magneto-optical recording medium, 11 ... Light transmissive substrate, 12 ... First dielectric layer, 13 ... First magnetism Layer, 1
4 ... 2nd magnetic layer, 15 ... 3rd magnetic layer, 15a ... Tb-F
e-Co film, 15b ... Gd-Fe-Co film, 16 ... Second
Dielectric layer, 17 ... Protective layer, 20A ... Second magneto-optical recording medium, 20B ... Magneto-optical recording medium obtained by partially deforming second magneto-optical recording medium, 21 ... Light transmissive substrate, 22 ... First Dielectric layer, 23 ... First magnetic layer, 24 ... Second magnetic layer, 25 ... Third
Magnetic layer, 26 ... Fourth magnetic layer, 26a ... Tb-Fe-C
o film, 26b ... Gd-Fe-Co film, 27 ... Second dielectric layer, 28 ... Protective layer, Tc11, Tc12, Tc13 ... Curie temperature of each of the first, second and third magnetic layers 13, 14, 15 , Tc21, Tc22, Tc23, Tc24 ... First,
Curie temperatures of the second, third and fourth magnetic layers 23, 24, 25 and 26.

Claims (4)

[Claims] 1. A first magnetic layer, a second magnetic layer, and a third magnetic layer are sequentially formed from a laser beam irradiation side, and an information signal is easily magnetized in a perpendicular direction by an external magnetic field while irradiating the laser beam during recording. After recording in the form of magnetic domains in the third magnetic layer having an axis, the magnetic domains are exchange-coupled to the first magnetic layer through the second magnetic layer, and the temperature is increased by irradiation of the laser beam during reproduction. In a magneto-optical recording medium in which the magnetization of the second magnetic layer is lost to cause domain wall movement so as to expand the exchange-coupled magnetic domain in the first magnetic layer, the first magnetic layer saturates a domain wall driving magnetic field. Gd- is set so that the normalized magnetic field normalized based on the magnetization is greater than 1.
An Fe film or a Gd-Fe-Co film is used as a base material, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is in the range of 28.0≤Gd≤29.0. The second magnetic layer is formed by using a material based on a Tb-Fe film or a Dy-Fe film and adding a nonmagnetic element such as Al and Cr or Co to form the second magnetic layer. The magnetic layer is a Tb-Fe-Co film or Dy-Fe film.
-Co film is used as a base material, and the element concentration ratio (at.% Ratio) of Tb or Dy to Fe-Co is 23.5≤Tb≤25.5 or 25.5≤Dy≤28. ．
The Curie temperatures Tc11, Tc12, and Tc13 of the first, second, and third magnetic layers are set to T by adjusting the addition amount of Co and nonmagnetic elements to each magnetic layer.
A magneto-optical recording medium, which is set so that c13>Tc11> Tc12. 2. A first direction, a second direction, a third direction, and a fourth magnetic layer are sequentially formed from a laser beam irradiation side, and an information signal is applied in a vertical direction by an external magnetic field while irradiating the laser beam during recording. After recording in the form of magnetic domains on the fourth magnetic layer having an easy axis of magnetization, the magnetic domains are recorded on the second and third magnetic layers.
The magnetic domains exchange-coupled in the first magnetic layer through exchange coupling with the first magnetic layer via the magnetic layer, and at least the magnetization of the third magnetic layer disappears due to a temperature rise due to irradiation of the laser beam during reproduction. In the magneto-optical recording medium in which the domain wall movement is generated so as to increase the magnetic field, the first magnetic layer has a normalized magnetic field obtained by normalizing the domain wall driving magnetic field based on the saturation magnetization so that Gd−
An Fe film or a Gd-Fe-Co film is used as the base material, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is in the range of 28.0≤Gd≤29.0. And the second and third magnetic layers are formed of a Tb-Fe film or a Dy-Fe film.
A film-based material is used to form a film by adding a non-magnetic element such as Al or Cr or Co, and the fourth magnetic layer is a Tb-Fe-Co film or a Dy-Fe film.
-Co film is used as a base material, and the element concentration ratio (at.% Ratio) of Tb or Dy to Fe-Co is 23.5≤Tb≤25.5 or 25.5≤Dy≤28. ．
The Curie temperatures Tc21, Tc22, Tc2 of the first, second, third and fourth magnetic layers are adjusted by adjusting the amount of Co or non-magnetic element added to each magnetic layer.
3, Tc24 is Tc24>Tc21>Tc22> Tc2
A magneto-optical recording medium characterized by being set to 3. 3. A first magnetic layer, a second magnetic layer, and a third magnetic layer are sequentially formed from a laser beam irradiation side, and an information signal is easily magnetized in a perpendicular direction by an external magnetic field while irradiating the laser beam during recording. After recording in the form of magnetic domains on the third magnetic layer having an axis, the magnetic domains are exchange-coupled to the first magnetic layer through the second magnetic layer, and the temperature is increased by irradiation of the laser beam during reproduction. In a magneto-optical recording medium in which the magnetization of the second magnetic layer is lost to cause domain wall movement so as to expand the exchange-coupled magnetic domain in the first magnetic layer, the first magnetic layer saturates a domain wall driving magnetic field. Gd- is set so that the normalized magnetic field normalized based on the magnetization is greater than 1.
An Fe film or a Gd-Fe-Co film is used as the base material, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is in the range of 28.0≤Gd≤29.0. The second magnetic layer is formed by using a material based on a Tb-Fe film or a Dy-Fe film and adding a nonmagnetic element such as Al or Cr or Co to form the third magnetic layer. The magnetic layer is composed of a Tb-Fe-Co film and a Gd-Fe-
Anti-parallel, which is stable when the directions of magnetization of the two-layer film are opposite to each other in a temperature region where the film is formed as a two-layer film including a Co film and reproduction is performed by moving the domain wall in the first magnetic layer. A magneto-optical recording medium characterized in that the coupling is maintained. 4. The first, second, third and fourth magnetic layers are formed in this order from the laser beam irradiation side, and the information signal is perpendicularly applied by an external magnetic field while irradiating the laser beam during recording. After recording in the form of magnetic domains on the fourth magnetic layer having an easy axis of magnetization, the magnetic domains are recorded on the second and third magnetic layers.
The magnetic domains exchange-coupled in the first magnetic layer through exchange coupling with the first magnetic layer via the magnetic layer, and at least the magnetization of the third magnetic layer disappears due to a temperature rise due to irradiation of the laser beam during reproduction. In the magneto-optical recording medium in which the domain wall movement is generated so as to increase the magnetic field, the first magnetic layer has a normalized magnetic field obtained by normalizing the domain wall driving magnetic field based on the saturation magnetization so that Gd−
An Fe film or a Gd-Fe-Co film is used as the base material, and the element concentration ratio (at.% Ratio) of Gd to Fe or Fe-Co is in the range of 28.0≤Gd≤29.0. And the second and third magnetic layers are formed of a Tb-Fe film or a Dy-Fe film.
A film-based material is used to form a film by adding a non-magnetic element such as Al or Cr or Co, and the fourth magnetic layer is formed of a Tb-Fe-Co film and a Gd-Fe- film.
Anti-parallel, which is stable when the directions of magnetization of the two-layer film are opposite to each other in a temperature region where the film is formed as a two-layer film including a Co film and reproduction is performed by moving the domain wall in the first magnetic layer. A magneto-optical recording medium characterized in that the coupling is maintained.