JPH06309708A - Magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a magneto-optical recording medium capable of high-sensitivity recording and high reproduction CNR and capable of light intensity modulation direct overwrite. [Structure] Five layers, that is, first magnetic layer to fifth magnetic layers 1 to 5 having perpendicular magnetic anisotropy are sequentially stacked on a substrate 6, and adjacent layers are exchange-coupled to each other. Curie temperatures of the magnetic layers 1 to 5 are T _c1 ,
If T _c2 , T _c3 , T _c4 , and T _c5 , then T _c1 > T
_{c2, T} c2 _<setting the composition of the _{T c4 <T c3, T c4} < respective magnetic layers so that the relation of _{T c5.}

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 capable of optical modulation direct overwriting and particularly capable of improving recording or reproducing characteristics.

[0002]

2. Description of the Related Art FIG. 4 to FIG. 5 show an arrangement of a conventional magneto-optical recording medium and an outline of a recording device for recording on the magneto-optical recording medium. Figure 4 shows, for example, "Journal of
Applied Physics (Journal of Applied Physi
cs) ", Vol. 67, No. 9, May 1, 1990, pages 4415-4416, showing the structure of the magneto-optical recording medium.
16 is a substrate, and 11 to 14 are first magnetic layers, second magnetic layers, third magnetic layers and fourth magnetic layers having perpendicular magnetic anisotropy formed on the substrate 16, respectively. Are coupled to adjacent layers by exchange force, and the substrate 16 and the magnetic layers 11 to 14 form a recording medium 18. Reference numeral 17 is a bias magnet that generates a bias magnetic field, 19 is a drive motor that drives the recording medium 18, 20 is a semiconductor laser that emits a laser light 21, and 22 is a laser light 21 that is emitted from the semiconductor laser 20 and is focused for recording. It is a condenser lens for irradiating the medium 18.

Next, the overwrite operation of the conventional magneto-optical recording medium configured as described above will be described. After the recording medium 18 is formed, the transition metal sublattice magnetizations of the second to fourth magnetic layers 12 to 14 are initially oriented upward only once,
The bias magnetic field is generated downward by the bias magnet 17. In FIG. 6, the arrow indicates the direction of the transition metal sublattice magnetization, the shaded area indicates the state in which domain walls are formed between the magnetic layers, and the blank indicates the state in which the temperature is raised above the Curie temperature and the ferromagnetism is lost. Shown respectively.

In FIG. 6, recording by the low power process (A) will be described first. When the output of the semiconductor laser 20 is increased from that during reproduction and the temperature of each magnetic layer in the focused spot of the laser light 21 is raised to near the Curie temperature of the first magnetic layer 11, the sublattice magnetization of the second magnetic layer 12 is changed. The direction is transferred to the first magnetic layer 11, and the direction of the sub-lattice magnetization of the first magnetic layer 11 is upward. At this time, the third and fourth magnetic layers 13 and 14 do not particularly contribute to the operation, and even if the magnetization of the third magnetic layer 13 disappears, they are returned to the same direction by the exchange force with the fourth magnetic layer 14. It is magnetized and the state "0" is recorded, that is, the low power process is performed.

Recording in the high power process (B) will be described below. When the temperature is raised to near the Curie temperature of the second magnetic layer 12 by irradiation of laser light in the same manner as in the low power process, the magnetizations of the first and third magnetic layers 11 and 13 disappear, but the magnetization of the fourth magnetic layer 14 disappears. The sublattice magnetization direction does not change. Since the magnetizations of the first and third magnetic layers 11 and 13 have disappeared, no exchange force is exerted, and the sublattice magnetization of the second magnetic layer 12 is directed downward by the bias magnetic field. further,
When the temperature is lowered below the Curie temperature of the first magnetic layer 11, the direction of the sub-lattice magnetization of the second magnetic layer 12 is transferred to the first magnetic layer 11,
The direction of the sub-lattice magnetization of the first magnetic layer 11 is downward. Then, when the temperature is lowered from the Curie temperature of the third magnetic layer 13, the direction of the sub-lattice magnetization of the third magnetic layer 13 is aligned with the direction of the sub-lattice magnetization of the fourth magnetic layer 14 and becomes upward. As the temperature further decreases, the direction of the sub-lattice magnetization of the second magnetic layer 12 is aligned with the direction of the sub-lattice magnetization of the fourth magnetic layer 14 through the third magnetic layer 13 and becomes upward, so that the state "1" is recorded, that is, A high power process is performed. As described above, overwriting becomes possible by modulating the recording laser intensity into at least two values.

On the other hand, a method of improving the reproducing CNR by using a GdFeCo film having a high Curie temperature for the first magnetic layer of a magneto-optical recording medium capable of optical modulation direct overwriting is disclosed in "Proceeding of the 1991 International Symposium on. Optical Memory (Proceedings of the 1991 International Symposium
on Optical Memory) ”on pages 55-57. In this magneto-optical recording medium, in order to realize the optical modulation direct overwrite operation, it is necessary to newly provide an external magnetic field generator called an initializing magnet that generates a magnetic field of 3 to 4 kOe, and the magneto-optical recording of the present invention. It is very different from the medium.

[0007]

The conventional magneto-optical recording medium is configured as described above, and the low power process is performed in the vicinity of the Curie temperature of the first magnetic layer 11 and the Curie temperature of the second magnetic layer 12 is also in the vicinity thereof. A high power process is performed at. The recording sensitivity can be improved by lowering the Curie temperatures of the first magnetic layer 11 and the second magnetic layer 12. However, in order to obtain sufficient recording / reproducing characteristics, there is a difference in the temperatures at which the low power process and the high power process are performed, that is, the first magnetic layer 11 and the second magnetic layer 12
It is necessary to provide a sufficient temperature difference between the Curie temperatures of. On the other hand, in a magnetic film having a low Curie temperature, there is a problem that the Curie temperature of the first magnetic layer 11 cannot be lowered because the Kerr rotation angle of the magneto-optical effect relating to the signal intensity is small and the recording / reproducing characteristics are deteriorated.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a magneto-optical recording medium having high sensitivity and high signal output.

[0009]

In the magneto-optical recording medium of the present invention, five layers from a first magnetic layer having a perpendicular magnetic anisotropy to a fifth magnetic layer are sequentially laminated on a substrate, and each layer is adjacent to each other. Are light intensity modulated direct
An overwritable magneto-optical recording medium, wherein each magnetic layer of the medium has T _c1 > T _c2 , T _c2 <T _c4 <T _c3 , and T
_c4 <T _c5 where T _c1 : Curie temperature of first magnetic layer T _c2 : Curie temperature of second magnetic layer T _c3 : Curie temperature of third magnetic layer T _c4 : Curie temperature of fourth magnetic layer T _c5 : Fourth 5 is related to the Curie temperature of the magnetic layer.

Further, in the magneto-optical recording medium of the present invention, due to the relation of the respective magnetic layers, Tc1 <Tc5 and Tc3 <
It is preferable that the relationship is Tc5.

Further, in the magneto-optical recording medium of the present invention, it is preferable that Tc4 <Tc1 be satisfied in relation to each of the magnetic layers.

Further, the magneto-optical recording medium of the present invention comprises the first
The magnetic layer is mainly composed of at least one element selected from the group consisting of rare earth metal elements Nd, Gd, Tb and Dy and at least one element selected from the group consisting of transition metal elements Fe and Co. It is preferably an alloy.

Further, the magneto-optical recording medium of the present invention comprises a second
The magnetic layer is an alloy mainly composed of at least one element selected from the group consisting of rare earth metal elements Tb and Dy and at least one element selected from the group consisting of transition metal elements Fe and Co. Is preferred.

Further, the magneto-optical recording medium of the present invention has a third aspect.
The magnetic layer is an alloy mainly composed of at least one element selected from the group consisting of rare earth metal elements Gd, Tb and Dy and at least one element selected from the group consisting of transition metal elements Fe and Co. Preferably there is.

In the magneto-optical recording medium of the present invention, the fourth magnetic layer has at least one element selected from the group consisting of rare earth metal elements Tb and Dy and the group consisting of transition metal elements Fe and Co. It is preferable that the alloy is mainly composed of at least one of the above-mentioned elements.

Further, in the magneto-optical recording medium of the present invention, the fifth magnetic layer has a rare earth metal element Tb and a transition metal element Fe.
An alloy mainly containing at least one element selected from the group consisting of and Co is preferable.

Further, the magneto-optical recording medium of the present invention is preferably provided with an intermediate layer between the second magnetic layer and the third magnetic layer for adjusting the exchange coupling force of both layers.

Further, the magneto-optical recording medium of the present invention is preferably provided with a Kerr effect enhancing layer and / or a protective film made of a dielectric material on at least one side of the magnetic film.

In the magneto-optical recording medium of the present invention, the first magnetic layer may be made of an alloy film of at least Pt or Pd and Co.

In the magneto-optical recording medium of the present invention, the first magnetic layer may be composed of a multi-layer film in which at least Pt or Pd and Co are laminated.

[0021]

In the magneto-optical recording medium of the present invention, five magnetic layers are formed and the direction of the sub-lattice magnetization of the first magnetic layer is exchange-coupled with the direction of the sub-lattice magnetization of the second magnetic layer. The Curie temperature of the first magnetic layer can be set high, the Curie temperatures of the second magnetic layer and the third magnetic layer can be set low, and the Curie temperatures of the second magnetic layer and the third magnetic layer can be set to the same. A sufficient temperature difference can be provided.
Therefore, high recording sensitivity can be realized, and by increasing the Curie temperature of the first magnetic layer, the Kerr rotation angle increases, and a high reproducing CNR (Carrier to Noise Ratio) can be obtained.

[0022]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing a magneto-optical recording medium according to an embodiment of the present invention. 6 is a transparent substrate made of glass or plastics, and 1 to 5 are first magnetic layers, second magnetic layers, third magnetic layers, fourth magnetic layers and fifth magnetic layers which are exchange-coupled to each other.
The magnetic layers 1 to 5 are magnetic layers, and are sequentially formed by sputtering on a transparent substrate 6 made of glass or plastics to form a recording medium 8. Reference numeral 7 is a bias magnet. Although not shown, a dielectric layer and a protective film are formed on both sides of the magnetic layer thus laminated.

The sub-lattice magnetization direction of the first magnetic layer 1 becomes the same as the sub-lattice magnetization direction of the second magnetic layer 2 due to the exchange force with the second magnetic layer 2, and the temperature rises due to laser light irradiation during reproduction. A material whose decrease in Kerr rotation angle due to
d _R1 Gd _R2 Tb _R3 Dy _R4 ) _x (Fe _1-y Co _y ) _1-x (R ₁
To R4 are 0 ≦ R1 to R4 ≦ 1, respectively, and R1 + R2 +
R3 + R4 = 1, 0.05 <x <0.3, 0 ≦ y ≦ 1) or the like and an alloy of a rare earth metal and a transition metal. More preferably, the range of x is 0.1 <x <0.25.

Further, it may be formed of an alloy of Pt or Pd and Co. In this case, there is an effect of improving the magneto-optical effect in the short wavelength region. further,
When this alloy film is formed by laminating Pt or Pd and Co by, for example, a binary simultaneous sputtering method, the alloy film may be alloyed by mixing with a short period. In this case, the same effect can be obtained.
The thickness of the first magnetic layer 1 may be in the range of 1 to 100 nm, more preferably 10 to 50 nm. If the film thickness is too thick, not only the laser power required for recording increases and the recording sensitivity decreases, but also the transfer characteristics in the sub-lattice magnetization direction from the second magnetic layer 2 deteriorate and the noise level increases, resulting in an increase in CNR. This is because if the film thickness decreases and the film thickness is too thin, a high reproduction CNR cannot be obtained.

The sub-lattice magnetization direction of the second magnetic layer 2 is determined by the exchange force with the sub-lattice magnetization direction of the third magnetic layer 3 when the temperature is lowered, and the Curie temperature T _c2 is the third magnetic layer 3 and the fourth magnetic layer 3. A material that is lower than the Curie temperatures T _c3 and T _{c4 of the} magnetic layer 4 and has a high coercive force for holding recorded information of “1” and “0”, for example (Tb _R5 Dy _R6 ) _{v
(Fe 1-w Co w)} 1-v (0 ≦ R5 ≦ 1,0 ≦ R6 ≦ 1 with R5 + R6 = 1,0.1 <v < 0.3,0 ≦ w ≦ 0.5) or the like is used. More preferably, the range of v is 0.2 <v <0.25. The thickness of the second magnetic layer 2 is 10 to 100n.
It may be in the range of m, and more preferably in the range of 10 to 50 nm. If the film thickness is too thick, not only the laser power required for recording increases and the recording sensitivity decreases, but also the transfer characteristics in the sub-lattice magnetization direction from the third magnetic layer 3 deteriorate and the recording magnetic field dependence deteriorates. This is because if the film thickness is too thin, the exchange force from the third magnetic layer 3 will be strong and the retention of magnetization will be unstable.

The third magnetic layer 3 is a layer whose sublattice magnetization direction is determined by the bias magnetic field in the high power process, and the Curie temperature T _c3 is the Curie temperatures T _c2 , T of the second magnetic layer 2 and the fourth magnetic layer 4. 5th higher than _c4
A material lower than the Curie temperature T _c5 of the magnetic layer 5, for example, (Gd _R7 Tb _R8 Dy _R9 ) _t (Fe _1-u Co _u ) _1-t (R 7-
R9 is 0 ≦ R7 to R9 ≦ 1, respectively, and R7 + R8 + R
9 = 1, 0.15 <t <0.4, 0.2 ≦ u ≦ 1) and the like are used. Particularly, it is preferable that the range of t is 0.2 <t <0.3, and further, Dy _t (Fe _1-u Co _u ) _1-t is preferable in controlling the magnetic characteristics such as the Curie temperature. The thickness of the third magnetic layer 3 may be in the range of 20 to 200 nm,
The range of -60 nm is preferred. This is because if the film thickness is too thick, the laser power required for recording will increase and the recording sensitivity will decrease, and if the film thickness is too thin, the transfer characteristics in the sub-lattice magnetization direction to the second magnetic layer 2 will deteriorate.

The fourth magnetic layer 4 blocks the exchange force between the third magnetic layer 3 and the fifth magnetic layer 5 at a high temperature where a high power process is performed, and at a low temperature, the third magnetic layer and the fifth magnetic layer 4 are cut off. A material having an exchange force with each other and having the same direction of the sublattice magnetization, and the Curie temperature T _c4 thereof is lower than the Curie temperature T _c3 of the third magnetic layer 3, for example, (Tb _R10 Dy _R11 ) _r (Fe _1-s C
o _{s) 1-r} (with 0 ≦ R10 ≦ 1,0 ≦ R11 ≦ 1 R10 + R11 =
1, 0.05 <r <0.4, 0 ≦ s ≦ 0.5) and the like are used.
More preferably, the range of r is 0.1 <r <0.2. The thickness of the fourth magnetic layer 4 may be in the range of 5 to 50 nm, and more preferably 8 to 30 nm. If the film thickness is too thick, the laser power required for recording will increase and the recording sensitivity will decrease, and if the film thickness is too thin, the third process in the high power process will occur.
The exchange force between the magnetic layer 3 and the fifth magnetic layer 5 cannot be blocked sufficiently.

The fifth magnetic layer 5 has a large perpendicular magnetic anisotropy in which the direction of the sublattice magnetization does not change in the high power process and has a Curie temperature T _c5 of 300 ° C. or higher, for example, Tb _p (Fe _1-q Co _q ) _1-p (0.15 <p <0.4, 0.3 ≦ q ≦
1) etc. are used. More preferably, the range of p is 0.2 <p <0.3. The film thickness of the fifth magnetic layer 5 is
It may be in the range of 20 to 200 nm, and more preferably in the range of 30 to 80 nm. If the film thickness is too thick, the laser power required for recording increases and the recording sensitivity decreases, and if the film thickness is too thin, the sub-lattice magnetization direction becomes unstable during recording and storage.

A dielectric layer (not shown) is used to increase the apparent Kerr rotation angle by utilizing the car enhancement effect and to reduce the noise level by reducing the reflectance to improve the reproduction CNR. Layer, Si, A
1, nitrides or oxides such as Ti, and mixtures thereof (SiNx, SiOx, AlOx, AlNx, T
iNx, GeNx, SiAlNx, SiAlON, etc.)
A dielectric film made of is used. The film thickness of the dielectric layer is determined by the refractive index of the material used (usually n = 2.0 to 2.5), and it is preferable to provide the laminated magnetic layer at a thickness of 50 to 80 nm at least on the substrate side.

Further, the protective layer is for improving the reliability of the magnetic film, and is made of the same material as that of the dielectric layer, and has a film thickness with high reliability without pinholes on both sides of the laminated magnetic layers. Is provided with a thickness of about 50 to 100 nm. When the above-mentioned dielectric layer is provided, it can serve as both the protective layer and the dielectric layer.

The above Curie temperature relationships of the magnetic layers are summarized as _follows : T _c1 > T _c2 , T _c2 <T _c4 <T _c3 , and T _c4 <T _c5 (1). By doing so, recording by the low power process and the high power process can be ensured with high sensitivity, and since T _c1 can be increased, the Kerr rotation angle becomes large during reproduction and the high CNR is achieved.
Can be obtained.

Relation of Curie temperature of each magnetic layer (1)
Then, by further _satisfying the relationship of T _c3 <T _c5 and T _c1 < _Tc5 (2), the stability of the fifth magnetic layer 5 is improved and a highly reliable magneto-optical recording medium can be obtained. (See Examples 37 to 39 described later).

The Curie temperatures of the respective magnetic layers (1) or (1) and (2) are further _satisfied by the relationship of T _c1 > T _c4 (3), that is, the first magnetic layer 1 By setting the Curie temperature high, the obtained reproduction signal strength is improved, and the magneto-optical recording medium having a higher reproduction CNR can be obtained (see Examples 1 to 19 and 22 to 33 described later).

Between the second magnetic layer 2 and the third magnetic layer 3, for example, (Gd _R12 Tb _R13 Dy _R14 Ho _R15 ) _{m.
(Fe 1-n Co n)} 1-m (R12~R15 each 0-1
Then, R12 + R13 + R14 + R15 = 1, 0.15 <m <0.4, 0
By providing an intermediate layer composed of a magnetic layer such as ≦ n ≦ 1), the exchange force between the second magnetic layer 2 and the third magnetic layer 3 can be adjusted, and after performing a high power process. In addition, it is possible to prevent an accident that the sublattice magnetization directions of the second magnetic layer 2 and the first magnetic layer 1 are reversed and the recording of "1" becomes "0" (see Examples 41 and 42 described later). . The range of m is more preferably 0.25 <m <0.35.

This intermediate layer is composed of the second magnetic layer 2 and the third magnetic layer 3.
Exchanging force between and (proportional to energy density of domain wall)
It is used to control (mainly reduce). In order to reduce the interface domain wall energy density, the second and third methods are used.
It is preferable to use a magnetic material or a non-magnetic material having a perpendicular magnetic anisotropy energy smaller than that of the magnetic material used for the magnetic layers 2 and 3. Therefore, when a rare earth-transition metal (RE-TM) amorphous alloy similar to the other first to fifth magnetic layers 1 to 5 is used, Gd is the main component in the rare earth metal having a small perpendicular magnetic anisotropy energy. RE-TM used as
Membranes are a particularly effective material.

The thickness of the intermediate layer is preferably 1 to 30 nm,
If the film thickness is too large, the recording sensitivity will decrease.

The material of each layer is Dy as the third magnetic layer.
Use of a FeCo ternary amorphous alloy and use of a TbFeCo ternary amorphous alloy for the fourth magnetic layer is effective in productivity because it facilitates control of magnetic characteristics such as the Curie temperature.

In the magneto-optical recording medium composed of these magnetic layers, high sensitivity capable of optical modulation overwriting and high reproducing CNR were realized.

Next, the overwrite operation of the magneto-optical recording medium of the present invention will be described with reference to FIG.

First, the low power process (A) will be described. The output of the semiconductor laser is increased from that during reproduction, and the temperature of each magnetic layer in the focused spot of the laser light is raised to near the Curie temperature of the second magnetic layer 2 or the Curie temperature of the fourth magnetic layer 4. The Curie temperature of the fourth magnetic layer 4 is set higher than the Curie temperature of the second magnetic layer 2. When the temperature of the second magnetic layer decreases to near the Curie temperature, the sub-lattice magnetization direction of the third magnetic layer 3 is transferred to the second magnetic layer 2, and the sub-lattice magnetization direction of the second magnetic layer 2 becomes upward. After that, the sub-lattice magnetization direction of the second magnetic layer 2 is changed to the first magnetic layer 1.
The exchange force of the magnetic field causes the sub-lattice magnetization direction of the first magnetic layer 1 to be upward. At this time, the fourth and fifth magnetic layers 4 and 5 do not particularly contribute to the overwrite operation, and even if the magnetization of the fourth magnetic layer 4 disappears, the fourth and fifth magnetic layers 4 and 5 are again replaced by the exchange force with the fifth magnetic layer 5. 5 is magnetized in the same direction as the sublattice magnetization direction of the magnetic layer 5, and the state “0”, that is, the low power process is performed.

Further, in the high power process (B) of FIG. 2, when the temperature is raised to near the Curie temperature of the third magnetic layer 3 by the irradiation of the laser beam in the same manner as in the low power process, the second and fourth magnetic layers are formed. Although the magnetization of 2 and 4 disappears,
The sublattice magnetization direction of the fifth magnetic layer 5 does not change. And
Since the magnetizations of the second and fourth magnetic layers 2 and 4 have disappeared, no exchange force is exerted, and the sublattice magnetization direction of the third magnetic layer 3 becomes downward due to the bias magnetic field. Next, when the temperature is lowered from the Curie temperature of the fourth magnetic layer 4, the sub-lattice magnetization direction of the fifth magnetic layer 5 is transferred to the fourth magnetic layer 4, and the sub-lattice magnetization direction of the fourth magnetic layer 4 becomes upward. . Further, when the temperature is lowered below the Curie temperature of the second magnetic layer 2, the sub-lattice magnetization direction of the third magnetic layer 3 is transferred to the second magnetic layer 2, and the sub-lattice magnetization direction of the second magnetic layer 2 becomes downward. When the temperature drops further,
The sub-lattice magnetization direction of the third magnetic layer 3 is aligned with the sub-lattice magnetization direction of the fifth magnetic layer 5 via the fourth magnetic layer 4 and is directed upward. Near room temperature, the exchange force between the second magnetic layer 2 and the third magnetic layer 3 is weaker than the coercive force of the second magnetic layer 2, so the sublattice magnetization direction of the second magnetic layer 2 and the first magnetic layer 1 is downward. As it is, the state “1”, that is, the high power process is performed. As described above, overwriting becomes possible by modulating the recording laser intensity into at least two values.

Next, the present invention will be described in more detail with reference to specific examples. Each of the constituent members was formed of the following materials (for specific element ratios (atomic ratios) of the alloy, see the examples described later).

Substrate 6: PC substrate with a groove having a thickness of 1.2 mm Dielectric layer: SiNx (refractive index n = 2.2) Film thickness 500Å First magnetic layer 1: GdFeCo ternary amorphous alloy film thickness 200Å Second magnetic layer 2: TbFe binary ternary amorphous alloy film thickness 200 Å Third magnetic layer 3: DyFeCo ternary amorphous alloy film thickness 300 Å Fourth magnetic layer 5: TbFeCo ternary amorphous alloy film thickness 150 Å Fifth magnetic layer 5: TbFeCo ternary amorphous alloy Film thickness 400Å Protective layer: SiNx Using the recording medium configured as described above, recording frequency 5
FIG. 3 shows the result of optical modulation overwrite by changing the recording power with a signal of MHz at a linear velocity of 7.54 m / sec, an applied magnetic field of 300 Oe and a pulse width of 100 nsec. In FIG. 3, the plot on the left side is the influence of the reproducing CNR due to the power of the laser beam at the time of reproducing, and is the reproducing CNR when the laser beam is irradiated with DC, and the plot on the right side is the low power and the high power changes. It shows the change of the reproduction CNR when the recording power is changed. The plot on the left side shows that the recording is broken and the reproduction CNR is deteriorated when the reproduction power is 2 mW or more. The FIG. 3 shows an example of a magneto-optical recording medium comprised of the magnetic layers of the composition of Example 1, as is clear from FIG. 3, playback in high power P _{H =} 6.5 mW CNR
A good CNR of 50.2 dB is obtained. At this time, the erase ratio in overwrite recording was also 40 dB or more.

The respective constituent members and the film thicknesses are the same (in Examples 41 and 42, there are 50 parts between the second magnetic layer and the third magnetic layer).
The reproducing CNR when the ratio (%) of each atom of the alloy of each magnetic layer is changed is shown below together with the recording power.

Example 1 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 ≧ 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 6.5 mW /3.5mW, playback CNR = 50.2dB

Example 2 First magnetic layer: Gd ₁₉ Fe ₆₈ Co ₁₃ T _c1 = 295 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 17 Fe 81 Co 2 T} c4 = 155 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = 6.5mW /3.5mW, playback CNR = 50.5dB

Example 3 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₁ Fe ₇₉ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /3.5mW, playback CNR = 50.3dB

Example 4 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₅ Fe ₇₅ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /3.5mW, playback CNR = 49.8dB

Example 5 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₃ Fe ₅₂ Co ₂₅ T _c3 = 290 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5 mW /3.5mW, playback CNR = 50.1dB

Example 6 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₆ Fe ₅₁ Co ₂₃ T _c3 = 270 ° C. the fourth magnetic _{layer: Tb 17 Fe 79 Co 4 T} c4 = 175 ℃ fifth magnetic _{layer: Tb 25 Fe 35 Co 40 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = 6.5mW /3.0mW, playback CNR = 50.2dB

Example 7 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₇ Fe ₄₉ Co ₂₄ T _c3 = 270 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5 mW /3.0mW, reproduction CNR = 50.2d
B

Example 8 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₁ Fe ₇₉ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₄ Co ₂₁ T _c3 = 240 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 6. 5mW / 3.0mW, reproduction CNR = 49.0d
B

Example 9 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₁ Fe ₇₉ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₃₀ Co ₄₅ T _c3> 300 ° C. fourth magnetic _{layer: Tb 17 Fe 81 Co 2 T} c4 = 155 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = _9.0mW /3.5mW, playback CNR = 47.5dB

[0054] [Example 10] The first magnetic _{layer: Gd 23 Fe 65 Co 12 T} c1 = 300 ℃ second magnetic _{layer: Tb 21 Fe 79 T c2 =} 150 ℃ third magnetic layer: _Dy 26 _Co 74 _{T c3>} 300 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 9.0 mW / 3.5 mW, playback CNR = 46.8dB

Example 11 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 14 Fe 83 Co 3 T} c4 = 160 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = 7.0mW /3.5mW, playback CNR = 50.2dB

Example 12 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₈ Fe ₈₀ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /3.5mW, playback CNR = 50.4dB

Example 13 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /4.0mW, playback CNR = 50.1dB

Example 14 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 17 Fe 78 Co 5 T} c4 = 185 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = 7.0mW /4.0mW, playback CNR = 50.3dB

Example 15 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₀ Co ₃ T _c4 = 165 ° C. Fifth magnetic layer: Tb ₂₃ Fe ₁₇ Co ₆₀ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5 mW /3.5mW, playback CNR = 50.2dB

Example 16 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₀ Co ₃ T _c4 = 165 ° C. Fifth magnetic layer: Tb ₂₆ Fe ₁₆ Co ₅₈ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /3.5mW, playback CNR = 50.0dB

Example 17 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₀ Co ₃ T _c4 = 165 ° C. Fifth magnetic layer: Tb ₂₃ Co ₇₇ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW / 3.5 mW, playback CNR = 49.9dB

Example 18 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₀ Co ₃ T _c4 = 165 ° C. Fifth magnetic layer: Tb ₂₆ Co ₇₄ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW / 3.5 mW, playback CNR = 50.1dB

Example 19 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 17 Fe 80 Co 3 T} c4 = 160 ℃ fifth magnetic _{layer: Tb 24 Fe 38 Co 38 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = 7.5mW /3.5mW, playback CNR = 50.2dB

Example 20 First magnetic layer: Gd ₂₀ Co ₈₀ T _c1 > 300 ° C. Second magnetic layer: Tb ₂₁ Fe ₇₉ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW / 4.0 mW, playback CNR = 46.0dB

Example 21 First magnetic layer: Gd ₂₃ Fe ₁₅ Co ₆₂ T _c1 > 300 ° C. Second magnetic layer: Tb ₂₁ Fe ₇₉ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /4.5mW, playback CNR = 47.1dB

Example 22 First magnetic layer: Gd ₁₂ Tb ₁₀ Fe ₆₀ Co ₁₈ T _c1 = 290 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₀ Co ₃ T _c4 = 170 ° C. Fifth magnetic layer: Tb ₂₅ Fe ₁₆ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 3.5mW, playback CNR = 49.0dB

Example 23 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₅ Co ₃ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₈ Co ₅ T _c4 = 185 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _{c 5} > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 3.5mW, reproduction CNR = 48.8dB

Example 24 First magnetic layer: Gd ₁₉ Fe ₆₈ Co ₁₃ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₄ Fe ₇₃ Co ₃ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₈ Co ₅ T _c4 = 185 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _{c 5} > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 4.0mW, playback CNR = 49.5dB

Example 25 First magnetic layer: Tb ₁₈ Fe ₆₃ Co ₁₉ T _c1 = 290 ° C. Second magnetic layer: Tb ₂₄ Fe ₇₃ Co ₃ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₈ Co ₅ T _c4 = 185 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _{c 5} > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 3.5mW, reproduction CNR = 48.5d
B

Example 26 First magnetic layer: Tb ₁₈ Fe ₆₉ Co ₁₃ T _c1 = 230 ° C. Second magnetic layer: Tb ₂₄ Fe ₇₃ Co ₃ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₈ Co ₅ T _c4 = 185 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _{c 5} > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 4.5mW, reproduction CNR = 47.1d
B

Example 27 First magnetic layer: Gd ₂₀ Fe ₆₇ Co ₁₃ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Gd ₈ Dy ₁₇ Fe ₅₇ Co ₁₈ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 4.0mW, reproduction CNR = 48.0dB

Example 28 First magnetic layer: Gd ₂₀ Dy ₃ Fe ₆₂ Co ₁₅ T _c1 = 290 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Gd ₈ Dy ₁₇ Fe ₅₇ Co ₁₈ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 8.0mW / 3.0mW, playback CNR = 48.2dB

Example 29 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Dy ₂₃ Fe ₇₀ Co ₇ T _c2 = 160 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 8.0mW / 3.5mW, playback CNR = 49.4dB

Example 30 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Tb ₅ Dy ₂₀ Fe ₅₇ Co ₁₈ T _c3 = 265 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _{c 5} > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 6.5mW / 3.5mW, reproduction CNR = 47.5dB

Example 31 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₅ Fe ₇₃ Co ₂ T _c2 = 160 ° C. Third magnetic layer: Tb ₅ Dy ₂₀ Fe ₅₇ Co ₁₈ T _c3 = 265 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0mW / 4.0mW, playback CNR = 47.2dB

Example 32 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₆ Fe ₅₁ Co ₂₃ T _c3 = 270 ° C. the fourth magnetic _{layer: Tb 15 Dy 2 Fe 78 Co} 5 T c4 = 170 ℃ fifth magnetic _{layer: Tb 25 Fe 35 Co 40 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H _{/ P} L = 6.5mW / 4.0mW, reproduction CNR = 48.5dB

Example 33 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₁₆ Dy ₃ Fe ₈₁ T _c2 = 120 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₆ Fe ₈₄ T _c4 = 150 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW /2.5mW, playback CNR = 46.7dB

Example 34 First magnetic layer: Nd ₁₀ Gd ₁₉ Fe ₅₅ Co ₁₆ T _c1 > 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Gd ₈ Dy ₁₇ Fe ₅₇ Co ₁₈ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 3.5mW, playback CNR = 47.1dB

Example 35 First magnetic layer: Pt ₇₇ Co ₂₃ T _c1 = 200 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5 mW / 3.0 mW, playback CNR = 47.5dB

Example 36 First magnetic layer: Pd ₇₆ Co ₂₄ T _c1 = 200 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.0 mW / 4.0 mW, playback CNR = 46.8dB

Example 37 First magnetic layer: Tb ₁₈ Fe ₇₈ Co ₄ T _c1 = 180 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₇ Fe ₄₈ Co ₂₅ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 17 Fe 77 Co 6 T} c4 = 190 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = 7.0mW /4.5mW, playback CNR = 45.5dB

Example 38 First magnetic layer: Tb ₁₈ Fe ₇₈ Co ₄ T _c1 = 180 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₆ Co ₂ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₄₈ Co ₂₇ T _c3 = 300 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₇ Co ₆ T _c4 = 190 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 7.5mW / 4.5mW, reproduction CNR = 45.3dB

Example 39 First magnetic layer: Tb ₁₅ Fe ₈₁ Co ₄ T _c1 = 175 ° C. Second magnetic layer: Tb ₂₃ Fe ₇₇ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₄₈ Co ₂₇ T _c3 = 300 ° C. the fourth magnetic _{layer: Tb 15 Fe 79 Co 6 T} c4 = 190 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> 300 ℃ recording reproducing characteristics: the recording power _P H / _{P L} = _8.0mW /3.5mW, playback CNR = 45.0dB

Example 40 First magnetic layer: Gd ₂₃ Fe ₆₀ Co ₁₇ T _c1 > 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₆ Co ₂ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₄₈ Co ₂₇ T _c3 = 300 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₇ Co ₆ T _c4 = 190 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₅₅ Co ₂₁ T _c5 = 290 ° C. Recording / reproducing characteristics: Recording power P _H / P _L = 8.0mW / 3.5mW, reproduction CNR = 46.5dB

Example 41 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Intermediate layer: Gd ₃₂ Fe ₆₃ Co ₅ T _c = 300 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ℃ recording reproducing characteristics: the recording power _{P H / P L = 8.0mW /} 4.0mW, reproduction CNR = 50.3dB

Example 42 First magnetic layer: Pt ₇₆ Co ₂₄ T _c1 = 200 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Intermediate layer: Gd ₃₂ Fe ₆₃ Co ₅ T _c = 300 C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₇₉ Co ₄ T _c4 = 175 ° C. Fifth magnetic layer: Tb ₂₅ Co ₇₅ T _c5 > 300 ° C. Recording / reproducing characteristics : recording power _{P H / P L = 8.0mW /} 3.5mW, playback CNR = 47.5dB

Comparative Example 1 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 17 Fe 83 T c4 =} 140 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> Curie temperature of 300 ° C. the fourth magnetic layer is not over-write operation low: T _c2 > T _c4

Comparative Example 2 First magnetic layer: Tb ₂₃ Fe ₇₇ T _c1 = 150 ° C. Second magnetic layer: Tb ₂₄ Fe ₇₃ Co ₃ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Low Curie temperature of the first magnetic layer: T _c1 <T _c2 , playback CNR = 38.5dB

Comparative Example 3 First magnetic layer: Dy ₂₀ Fe ₈₀ T _c1 = 80 ° C. Second magnetic layer: Tb ₂₄ Fe ₇₃ Co ₃ T _c2 = 170 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Low Curie temperature of the first magnetic layer: T _c1 <T _c2 , playback CNR = 28.5dB

Comparative Example 4 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₄ Fe ₅₆ Co ₂₀ T _c3 = 245 ° C. the fourth magnetic _{layer: Tb 17 Fe 58 Co 25 T} c4 = 260 ℃ fifth magnetic _{layer: Tb 24 Fe 17 Co 59 T} c5> Curie temperature of 300 ° C. the fourth magnetic layer is not high over-write operation : T _c3 <T _c4

Comparative Example 5 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₆₁ Co ₁₇ T _c2 = 280 ° C. Third magnetic layer: Dy ₂₄ Fe ₅₆ Co ₂₀ T _c3 = 245 ° C. Fourth magnetic layer: Tb ₁₈ Fe ₆₃ Co ₁₉ T _c4 = 290 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. High Curie temperature of the second magnetic layer and overwrite operation Without: T _c2 > T _c3

Comparative Example 6 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₄ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Dy ₁₇ Fe ₈₃ T _c4 = 80 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. Curie temperature of the fourth magnetic layer is low and overwrite operation is not performed: T _c4 <T _c2

Comparative Example 7 First magnetic layer: Gd ₂₃ Fe ₆₅ Co ₁₂ T _c1 = 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. the fourth magnetic _{layer: Tb 17 Fe 79 Co 4 T} c4 = 175 ℃ fifth magnetic layer: Curie temperature of _{Tb 24 Fe 73 Co 3 T c5} = 170 ℃ fifth magnetic layer is not over-write operation low : T _c4 > T _c5

Comparative Example 8 First magnetic layer: Fe ₇₀ Co ₃₀ T _c1 > 300 ° C. Second magnetic layer: Tb ₂₂ Fe ₇₈ T _c2 = 150 ° C. Third magnetic layer: Dy ₂₅ Fe ₅₁ Co ₂₄ T _c3 = 280 ° C. Fourth magnetic layer: Tb ₁₇ Fe ₈₁ Co ₂ T _c4 = 155 ° C. Fifth magnetic layer: Tb ₂₄ Fe ₁₇ Co ₅₉ T _c5 > 300 ° C. The first magnetic layer is a transition metal only. Reproduction CNR = 25.2 dB

The same effect can be obtained by using the above-mentioned magneto-optical recording medium bonded with an adhesive or the like to form a double-sided medium or by adding a layer such as an ultraviolet curable resin on the protective layer. . In addition, Al and C are added to the magnetic layers of the above-described magneto-optical recording medium to the extent that the magnetic characteristics are not significantly changed.
The same effect can be obtained by adding a small amount of another element such as r.

[0096]

As described above, according to the present invention, by setting the Curie temperature from the first magnetic layer to the fifth magnetic layer exchange-coupled to each other, a high reproducing CNR with high recording sensitivity can be obtained.
It is possible to obtain a magneto-optical recording medium which is capable of optical modulation and direct overwriting.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a magneto-optical recording medium according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a recording operation on the magneto-optical recording medium shown in FIG.

FIG. 3 CNR when the recording laser power is changed
FIG. 6 is a characteristic diagram showing the recording power dependence of FIG.

FIG. 4 is a configuration diagram showing a conventional magnetic recording medium.

5 is a perspective view showing an outline of a recording device for recording on the magneto-optical recording medium shown in FIG.

FIG. 6 is a schematic diagram for explaining a recording operation on the magneto-optical recording medium shown in FIG.

[Description of Reference Signs] 1 first magnetic layer 2 second magnetic layer 3 third magnetic layer 4 fourth magnetic layer 5 fifth magnetic layer 6 substrate 8 recording medium

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Tsutsumi 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation

Claims (12)

[Claims] 1. A light intensity modulation direct over device in which five layers from a first magnetic layer to a fifth magnetic layer having perpendicular magnetic anisotropy are sequentially stacked on a substrate, and adjacent layers are exchange-coupled to each other. A writable magneto-optical recording medium, wherein each magnetic layer of the medium has T _c1 > T _c2 , T _c2 <T _c4 <T _c3 , and T
_c4 <T _c5 where T _c1 : Curie temperature of the first magnetic layer T _c2 : Curie temperature of the second magnetic layer T _c3 : Curie temperature of the third magnetic layer T _c4 : Curie temperature of the fourth magnetic layer T _c5 : Fourth 5 Magneto-optical recording medium having a relationship of Curie temperature of magnetic layer. 2. Due to the relationship of each magnetic layer, T _c1 <
The magneto-optical recording medium according to claim 1, wherein T _c5 and T _c3 <T _c5 . 3. Due to the relationship of each magnetic layer, T _c4 <
The magneto-optical recording medium according to claim 1, which has a relationship of T _c1 . 4. The first magnetic layer is a rare earth metal element Nd, G.
3. An alloy mainly containing at least one element selected from the group consisting of d, Tb and Dy and at least one element selected from the group consisting of transition metal elements Fe and Co. Alternatively, the magneto-optical recording medium described in 3 above. 5. The second magnetic layer comprises at least one element selected from the group consisting of rare earth metal elements Tb and Dy,
The magneto-optical recording medium according to claim 1, which is an alloy mainly containing at least one element selected from the group consisting of transition metal elements Fe and Co. 6. The third magnetic layer is a rare earth metal element Gd, Tb.
4. An alloy mainly composed of at least one element selected from the group consisting of and Dy and at least one element selected from the group consisting of transition metal elements Fe and Co. Magneto-optical recording medium. 7. The fourth magnetic layer comprises at least one element selected from the group consisting of rare earth metal elements Tb and Dy,
The magneto-optical recording medium according to claim 1, which is an alloy mainly containing at least one element selected from the group consisting of transition metal elements Fe and Co. 8. The Tb in which the fifth magnetic layer is a rare earth metal element.
4. The magneto-optical recording medium according to claim 1, which is an alloy mainly containing at least one element selected from the group consisting of transition metal elements Fe and Co. 9. The magneto-optical recording medium according to claim 1, wherein an intermediate layer for adjusting the exchange coupling force of both layers is provided between the second magnetic layer and the third magnetic layer. 10. The magneto-optical recording medium according to claim 1, wherein a Kerr effect enhancing layer made of a dielectric material and / or a protective film is provided on at least one side of the magnetic film. 11. The first magnetic layer comprises at least Pt or P.
The magneto-optical recording medium according to claim 1, comprising an alloy film of d and Co. 12. The first magnetic layer comprises at least Pt or P
4. The magneto-optical recording medium according to claim 1, which is composed of a multilayer film in which d and Co are laminated.