Source: https://patents.google.com/patent/US6399227B1/en
Timestamp: 2018-09-24 22:23:29
Document Index: 122055622

Matched Legal Cases: ['art 15', 'art 15', 'art 15', 'art 36', 'art 55', 'art 55', 'art 55', 'art 96']

US6399227B1 - Magneto-optical recording medium - Google Patents
US6399227B1
US6399227B1 US08160976 US16097693A US6399227B1 US 6399227 B1 US6399227 B1 US 6399227B1 US 08160976 US08160976 US 08160976 US 16097693 A US16097693 A US 16097693A US 6399227 B1 US6399227 B1 US 6399227B1
US08160976
Yoshihiko Kudoh
Yuuichi Fukamachi
Masahiro Birukawa
H 1-2 =σw/2M 1 t 1
and the exchange-coupling force H2-1 seen from the supporting magnetic film 152 is represented by the following equation:
H 2-1 =σw/2M 2 t 2
At room temperature, the following relationships are obtained: Hc1>H1-2, Hc2>H2-1, and Hc2+H2-1<Hi<Hc1, and the magnetization direction of the supporting magnetic film 152 is aligned with a direction of the initializing magnetic field (Hi) 153.
In FIG. 1B, an arrow 10 indicates a direction of an initializing magnetic field Hi at a position distant from a light spot, an arrow 11 indicates a direction of a recording magnetic field Hw, and lines 12 indicate recording light or readout light. Referring to FIGS. 1A and 1B, the MO recording medium in this example includes a substrate 13 made of polycarbonate, protective layers 14 and 18 made of SiN films, a readout magnetic film 15, a controlling magnetic film 16, a recording magnetic film 17, and recorded magnetic domains 19. The readout magnetic film 15 is made of a perpendicular magnetic anisotropy GdTbFeCo film having a Curie temperature Tc1 and a coercivity Hc1. The controlling magnetic film 16 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc2 which is an in-plane magnetic anisotropy film at room temperature and has a compensation temperature Tcomp2 at about 150° C. The recording magnetic film 17 is made of a perpendicular magnetic anisotropy TbFeCo film having a Curie temperature Tc3 and a coercivity Hc3. The readout magnetic film 15 and the recording magnetic film 17 are exchange-coupled via the controlling magnetic film 16, and these three magnetic films constitute a recording layer 20. The respective films on the substrate 13 are formed by a sputtering system or a vacuum evaporation system. The thicknesses of the protective layers 14 and 18 are set to be 80 nm. The thicknesses of the readout magnetic film 15, the controlling magnetic film 16, and the recording magnetic film 17 are set to be 40 nm, 5-15 nm, and 50 nm, respectively. The Curie temperatures Tc1, Tc2, and Tc3 are set to be about 300° C., 300° C. or more, and about 230° C., respectively. The coercivities Hc1 and Hc3 are set to be 1.5-2 kOe, and 10-20 kOe at room temperature, respectively.
When the temperature of a part 15 a of the readout magnetic film 15 is increased to 130° C. or a higher temperature, i.e., when the temperature of a part 15 a is increased to about the compensation temperature (150° C.) of the controlling magnetic film 16, the exchange-coupling force suppressing effect of the controlling magnetic film 16 is reduced. Thus, the exchange-coupling force H1-3 is increased to about 1-2.6 kOe, so that the conditions of Hc1<H1-3, and Hc3>H3-1 can easily be established. Therefore, the magnetization direction of the part 15 a of the readout magnetic film 15 is aligned with the magnetization direction of the recording magnetic film 17. As a result, the recorded magnetic domains 19 of the recording magnetic film 17 are transferred to the readout magnetic film 15.
As described above, the recorded information can be detected as a readout signal from the high-temperature region 22 having a temperature of 130° C. or higher of the readout light spot 21. This means that a recorded magnetic domain having a length smaller than the diameter of the readout light spot can be read out without a signal interference of the recorded magnetic domain positioned forward.
In FIG. 3B, an arrow 30 indicates a direction of an initializing magnetic field Hi at a position distant from a light spot, an arrow 31 indicates a direction of a readout magnetic field Hr, an arrow 32 indicates a direction of a recording magnetic field Hw, and lines 33 indicate recording light or readout light. Referring to FIGS. 3A and 3B, the MO recording medium in this example includes a substrate 34 made of polycarbonate, protective layers 35 and 40 made of ZnS films, a readout magnetic film 36, a switching magnetic film 37, a controlling magnetic film 38, a recording magnetic film 39, and recorded magnetic domains 41. The readout magnetic film 36 is made of a perpendicular magnetic anisotropy GdFeCo film having a Curie temperature Tc1 and a coercivity Hc1. The switching magnetic film 37 is made of a perpendicular magnetic anisotropy TbFeCo film having a Curie temperature Tc2 and a coercivity Hc2 The controlling magnetic film 38 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc3 which is an in-plane magnetic anisotropy film at room temperature and has a compensation temperature Tcomp3 at about 130° C. The recording magnetic film 39 is made of a perpendicular magnetic anisotropy TbFeCo film having a Curie temperature Tc4 and a coercivity Hc4. The readout magnetic film 36 and the recording magnetic film 39 are exchange-coupled via the switching magnetic film 37 and the controlling magnetic film 38, and these four magnetic films constitute a recording layer 42. The respective films on the substrate 34 are formed by a sputtering system or a vacuum evaporation system. The thicknesses of the protective layers 35 and 40 are set to be 80 nm. The thicknesses of the readout magnetic film 36, the switching magnetic film 37, the controlling magnetic film 38, and the recording magnetic film 39 are set to be 35 nm, 10 nm, 5-15 nm, and 45 nm, respectively. The Curie temperatures Tc1, Tc2, Tc3, and Tc4 are set to be 300° C. or more, about 150° C., 300° C. or more, and about 250° C., respectively. The coercivities Hc1, Hc2, and Hc4 are set to be about 100 Oe, 1.5 kOe, and 10-20 koe at room temperature, respectively.
As is seen from the relationships in FIG. 4, even if the temperature of the recording layer 42 is increased by the irradiation of the readout light, in the region at about 110° C. or less, the condition of Hc2>H2-4 is still established by the influence of the exchange-coupling force suppressing effect of the controlling magnetic film 38. Therefore, the transfer of the recorded magnetic domains 41 from the recording magnetic film 39 to the switching magnetic film 37 does not occur. As a result, the transfer of the recorded magnetic domains 41 to the readout magnetic film 36 which is coupled with the switching magnetic film 37 by the exchange-coupling force H1-2 does not occur.
In the region in which the temperature of the recording layer 42 is increased to about 110° C. or more, i.e., when the temperature of the region of the recording layer 42 is increased to about the compensation temperature (130° C.) of the controlling magnetic film 38, the exchange-coupling force suppressing effect of the controlling magnetic film 38 is reduced. Thus, the exchange-coupling force H2-4 is increased to about 1-2.6 kOe, so that the conditions of Hc2<H2-4, and Hc4>H4-2 can easily be established. Meanwhile, the magnetization direction of the readout magnetic film 36 is aligned with the magnetization direction of the switching magnetic film 37 by the exchange-coupling force H1-2. As a result, in such a region, the magnetization direction of a part 36a of the readout magnetic film 36 is aligned with the magnetization direction of the recording magnetic film 39 by the exchange-coupling force H1-4 via the switching magnetic film 37 and the controlling magnetic film 38. Therefore, the recorded magnetic domains 41 of the recording magnetic film 39 are transferred to the readout magnetic film 36.
In the region in which the temperature of recording layer 42 is increased to about 150° C. or more, i.e., when the temperature of the region is increased to about the Curie temperature (about 150° C.) of the switching magnetic film 37, the magnetization of the switching magnetic film 37 is lost. Thus, the exchange-coupling between the readout magnetic film 36 and the recording magnetic film 39 in this region is cut off. As is seen from FIG. 4, since Hr>Hc1 the magnetization direction of the readout magnetic film 36 in this region is aligned with the direction of the readout magnetic film Hr. That is, in this region, the readout magnetic film 36 has no recorded magnetic domain 41.
As described above, by the readout light having the intensity by which the maximum temperature of the irradiated region is about 150° C. or more, the recorded information can be detected as a readout signal from the high-temperature region 44 having temperatures from 110° C. or more to 150° C. or less of the readout light spot 43. This means that a recorded magnetic domain having a length smaller than the diameter of the readout light spot can be read out without signal interference of the recorded magnetic domains positioned forward and rearward.
Alternatively, the controlling magnetic film 38 in FIGS. 3A and 3B may be made of a ferrimagnetic film which is an in-plane magnetic anisotropy film at room temperature, which has a compensation temperature Tcomp3 which is set to be about a temperature at which the transfer occurs (e.g., about 110° C.), and which has a Curie temperature Tc3 which is higher than the transfer temperature and equal to or lower than the highest temperature in the readout light irradiation region (e.g., about 150° C.). In such a case, the controlling magnetic film 38 can serve as the switching magnetic film 37, so that the above operation can be implemented with a construction in which the switching magnetic film 37 is omitted. In this case, a TbFeCo film, a DyFeCo film, an HoFeCo film, or the like is suitable for the controlling magnetic film 38.
In FIG. 5B, an arrow 51 indicates a direction of a recording magnetic field Hw, and lines 52 indicate recording light or readout light. Referring to FIGS. 5A and 5B, the MO recording-medium in this example includes a substrate 53 made of polycarbonate, protective layers 54 and 58 made of SiN films, a readout magnetic film 55, a controlling magnetic film 56, a recording magnetic film 57, and recorded magnetic domains 59. The readout magnetic film 55 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc1 which is an in-plane magnetic anisotropy film at room temperature and a perpendicular magnetic anisotropy film at about 130° C. around its compensation temperature Tcomp1 which is nearly equal to 160° C. The controlling magnetic film 56 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc2 which is an in-plane magnetic anisotropy film at room temperature and has a compensation temperature Tcomp2 at about 150° C. The recording magnetic film 57 is made of a perpendicular magnetic anisotropy TbFeCo film having a Curie temperature Tc3 and a coercivity Hc3. The readout magnetic film 55 and the recording magnetic film 57 are exchange-coupled via the controlling magnetic film 56, and these three magnetic films constitute a recording layer 60. The respective films on the substrate 53 are formed by a sputtering system or a vacuum evaporation system. The thicknesses of the protective layers 54 and 58 are set to be 80 nm. The thicknesses of the readout magnetic film 55, the controlling magnetic film 56, and the recording magnetic film 57 are set to be 40 nm, 5-10 nm, and 50 nm, respectively. The Curie temperatures Tc1, Tc2, and Tc3 are 300° C. or more, 300° C. or more, and about 230° C., respectively. The coercivity Hc3 is set to be 10-20 kOe at room temperature.
FIG. 6 shows the relationship between the Gd composition of the GdFeCo film and the compensation temperature. The value of Tcomp1 is substantially determined by the Gd composition ratio. Specifically, when the Gd composition is 23-28 at %, Tcomp1 is 80-260° C. Considering the intensity of the readout light, the above range is sufficient for the Gd composition of the readout magnetic film 55.
When the composition of the readout magnetic film 55 is Gd0.25Fe0.39Co0.36, the compensation temperature Tcomp1 is about 160° C. and the perpendicular external magnetic field necessary for directing the magnetization perpendicularly at room temperature is about 2 kOe.
When the temperature of a part 55 a of the readout magnetic film 55 is increased to about 130° C. or a higher temperature, i.e., when the temperature of a part 55 a is increased to about the compensation temperature (160° C.) of the readout magnetic film 55 and the compensation temperature (150° C.) of the controlling magnetic film 56, the readout magnetic film 55 becomes a perpendicular magnetic anisotropy film having a coercivity Hc1 (about 150 Oe), and the exchange-coupling force suppressing effect of the controlling magnetic film 56 is reduced. Thus, the exchange-coupling force H1-3 is increased to about 1.8 kOe, and all the magnetization in the thickness direction of the readout magnetic film 55 is perpendicular, so that the conditions of Hc1<H1-3, and Hc3>H3-1 can easily be established. Therefore, the magnetization direction of the part 55 a of the readout magnetic film 55 is aligned with the magnetization direction of the recording magnetic film 57. As a result, the recorded magnetic domains 59 of the recording magnetic film 57 are transferred to the readout magnetic film 55.
As described above, the recorded information can be detected as a readout signal from the high-temperature region 62 having a temperature of about 130° C. or higher of the readout light spot 61. This means that a recorded magnetic domain having a length smaller than the diameter of the readout light spot can be read out without a signal interference of the recorded magnetic domain positioned forward.
In FIG. 10B, an arrow 91 indicates a direction of a readout magnetic field Hr, an arrow 92 indicates a direction of a recording magnetic field Hw, and lines 93 indicate recording light or readout light. Referring to FIGS. 10A and 10B, the MO recording medium in this example includes a substrate 94 made of polycarbonate, protective layers 95 and 100 made of SiON films, a readout magnetic film 96, a controlling magnetic film 97, a switching magnetic film 98, a recording magnetic film 99, and recorded magnetic domains 101. The readout magnetic film 96 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc1 which is an in-plane magnetic anisotropy film at room temperature and a perpendicular magnetic anisotropy film at about 110° C. around its compensation temperature Tcomp1 which is nearly equal to 140° C. The controlling magnetic film 97 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc2 which is an in-plane magnetic anisotropy film at room temperature and has a compensation temperature Tcomp2 at about 130° C. The switching magnetic film 98 is made of a perpendicular magnetic anisotropy GdTbFe film having a Curie temperature Tc3 and a coercivity Hc3 The recording magnetic film 99 is made of a perpendicular magnetic anisotropy TbFeCo film having a Curie temperature Tc4 and a coercivity Hc4. The readout magnetic film 96 and the recording magnetic film 99 are exchange-coupled via the controlling magnetic film 97 and the switching magnetic film 98, and these four magnetic films constitute a recording layer 102. The respective films on the substrate 94 are formed by a sputtering system or a vacuum evaporation system. The thicknesses of the protective layers 95 and 100 are set to be 100 nm. The thicknesses of the readout magnetic film 96, the controlling magnetic film 97, the switching magnetic film 98, and the recording magnetic film 99 are set to be 40 nm, 5-10 nm, 10 nm, and 45 nm, respectively. The Curie temperatures Tc1, Tc2, Tc3, and Tc4 are set to be 300° C. or more, 300° C. or more, about 150° C., and about 250° C., respectively. The coercivities Hc3 and Hc4 are set to be about 1 kOe, and 10-20 kOe at room temperature, respectively.
The readout magnetic film 96 which is an in-plane magnetic anisotropy film at room temperature and a perpendicular magnetic anisotropy film at about 110° C. around Tcomp1 which is nearly equal to 140° C. can be realized by the composition of Gd0.245Fe0.39Co0.365.
Even if the temperature of the recording layer 102 is increased by the irradiation of the readout light, in the region at about 110° C. or less, the readout magnetic film 96 is still the in-plane magnetic anisotropy film. Thus, the magnetization of the readout magnetic film 96 on the side on which the readout light is incident is maintained to be in the in-plane magnetic state because it is not affected by H1-4 due to the exchange-coupling force effect of the controlling magnetic film 97. As a result the recorded magnetic domain 101 cannot be detected in the readout magnetic film 96.
In the region in which the temperature of the recording layer 102 is increased to about 110° C. or more, i.e., when the temperature of the region of the recording layer 102 is increased to about the compensation temperature (140° C.) of the readout magnetic film 96 and the compensation temperature (130° C.) of the controlling magnetic film 97, the readout magnetic film 96 becomes the perpendicular magnetic anisotropy film having a coercivity Hc1 (about 150 Oe). In addition, the exchange-coupling force suppressing effect of the controlling magnetic film 97 is reduced. Thus, the exchange-coupling force H1-4 is increased to about 1-2 kOe, and all the magnetization in the thickness direction of the readout magnetic film 96 becomes perpendicular. As a result, the conditions of Hc1<H1-4, and Hc4>H4-1 can easily be established. In addition, at this time, Hc3<H3-4, so that the magnetization direction of the switching magnetic film 98 is aligned with the magnetization direction of the recording magnetic film 99 by the exchange-coupling force H3-4. Therefore, in this region, the magnetization direction of a part 96 a of the readout magnetic film 96 is aligned with the magnetization direction of the recording magnetic film 99 by the exchange-coupling force H1-4 via the controlling magnetic film 97 and the switching magnetic film 98. As a result, the recorded magnetic domain 101 of the recording magnetic film 99 is transferred to the readout magnetic film 96.
In the region in which the temperature of recording layer 102 is increased to about 150° C. or more, i.e., when the temperature of the region is increased to the Curie temperature (about 150° C.) of the switching magnetic film 98 or more, the magnetization of the switching magnetic film 98 is lost. Thus, the exchange-coupling between the readout magnetic film 96 and the recording magnetic film 99 in this region is cut off. The coercivity Hc1 is about 150 Oe, and the coercivity Hc2 of the controlling magnetic film 97 in the perpendicular direction is very small, so that Hr>Hc1+Hc2. AS a result, the magnetization direction of the readout magnetic film 96 in this region is aligned with the direction of the readout magnetic field Hr. That is, in this region, the readout magnetic film 96 has no recorded magnetic domains 101.
As described above, by the readout light having the intensity by which the maximum temperature of the irradiated region is about 150° C. or more, the recorded information can be detected as a readout signal from the high-temperature region 104 having temperatures from 110° C. or more to 150° C. or less of the readout light spot 103. This means that a recorded magnetic domain having a length smaller than the diameter of the readout light spot can be read out without a signal interference of the recorded magnetic domains positioned forward and rearward.
Alternatively, the controlling magnetic film 97 in FIGS. 10A and 10B may be made of a ferrimagnetic film which is an in-plane magnetic anisotropy film at room temperature, which has a compensation temperature Tcomp3 which is set to be about a temperature at which the transfer occurs (e.g., about 110° C.), and which has a Curie temperature Tc2 which is higher than the transfer temperature and equal to or lower than the highest temperature in the readout light irradiation region (e.g., about 150° C.). In such a case, the controlling magnetic film 97 can serve as the switching magnetic film 98, so that the above operation can be implemented with a construction in which the switching magnetic film 98 is omitted. In this case, a TbFeCo film, a DyFeCo film, an HoFeCo film, or the like is suitable for the controlling magnetic film 97.
In FIG. 11B, an arrow 110 indicates a direction of an initializing magnetic field Hi, an arrow 111 indicates a direction of a recording magnetic field Hw, and lines 112 indicate recording light or readout light. Referring to FIGS. 11A and 11B, the MO recording medium in this example includes a substrate 113 made of polycarbonate, protective layers 114 and 118 made of SiN films, a recording/readout magnetic film 115, a controlling magnetic film 116, a supporting magnetic film 117, and recorded magnetic domains 119. The recording/readout magnetic film 115 is made of a perpendicular magnetic anisotropy TbFeCo film having a Curie temperature Tc1 and a coercivity Hc1. The controlling magnetic film 116 is made of a ferrimagnetic GdFeCo film having a Curie temperature Tc2 which is an in-plane magnetic anisotropy film at room temperature and has a compensation temperature Tcomp2 at about 190° C. The supporting magnetic film 117 is made of a perpendicular magnetic anisotropy GdTbFeCo film having a Curie temperature Tc3 and a coercivity Hc3. The recording/readout magnetic film 115 and the supporting magnetic film 117 are exchange-coupled via the controlling magnetic film 116, and these three magnetic films constitute a recording layer 120. The respective films on the substrate 113 are formed by a sputtering system or a vacuum evaporation system. The thicknesses of the protective layers 114 and 118 are set to be 80 nm. The thicknesses of the recording/readout magnetic film 115, the controlling magnetic film 116, and the supporting magnetic film 117 are set to be 50 nm, 5-15 nm, and 50 nm, respectively. The Curie temperatures Tc1, Tc2, and Tc3 are set to be about 190° C., 300° C. or more, and about 260° C., respectively. The coercivities Hc1 and Hc3 are set to be about 10-20 kOe, and about 1.5 kOe at room temperature, respectively.
In the case of the low-level recording light, the temperature of the recording layer 120 is increased to be about the Curie temperature Tc1 (190° C.) of the recording/readout magnetic film 115 by the recording light irradiation. In this case, Hc1 becomes very small, and the exchange-coupling force suppressing effect of the controlling magnetic film 116 is decreased at about the compensation temperature (190° C.) of the controlling magnetic film 116. Accordingly, the exchange-coupling force H1-3 becomes about 500 Oe, so that the conditions of Hc1+Hw<H1-3 and Hc3>H3-1 can be easily established. Therefore, the direction of the initial magnetization of the supporting magnetic film 117 is transferred to the magnetization of the recording/readout magnetic film 115. Thus, the low-level recording operation performs the erasing of the recording/readout magnetic film 115.
In the case of the high-level recording light, the temperature of the recording layer 120 is increased to be about the Curie temperature Tc3 (260° C.) of the supporting magnetic film 117 by the recording light irradiation. In this case, the magnetization of the supporting magnetic film 117 is directed in the direction of the recording magnetic field Hw. Thereafter, in the cooling process, when the temperature of the recording layer 120 reaches about the Curie temperature Tc1 (190° C.) of the recording/readout magnetic film 115, the conditions of Hc1+Hw<H1-3 and Hc3>H3-1 are satisfied. Therefore, the recorded magnetization of the supporting magnetic film 117 is transferred to the recording/readout magnetic film 115 by the exchange-coupling force H1-3. Thus, by the high-level recording operation, recorded domains 119 are formed on the recording/readout magnetic film 115.
The readout magnetic film 55 is a ferrimagnetic GdFeCo film having a Curie temperature of 300° C. or more which is an in-plane magnetic anisotropy film at room temperature and a perpendicular magnetic anisotropy film at about 100° C. around its compensation temperature Tcomp1 which is nearly equal to 120° C. The thickness of the readout magnetic film 55 is set to be 70 nm.
With the above structure, by modulating the power of the recording light between the low level and the high level, the overwrite can be performed on the recording magnetic film 115. When the temperature of the recording layer 120 is increased to be 100° C. or more by the readout light irradiation, the recorded magnetic domains 119 in the recording magnetic film 115 are transferred to the readout magnetic film 55. Thus, the super resolution readout can also be realized.
1. A magneto-optical recording medium comprising recording means for recording information and a substrate for supporting said recording means,
wherein said recording means includes:
a recording magnetic film for recording the information, said recording magnetic film being formed of a perpendicular magnetic anisotropy film; and
a readout magnetic film for optically reading out the information, said readout magnetic film being capable of being magnetically coupled with said recording magnetic film by an exchange-coupling force;
wherein said readout magnetic film has in-plane magnetic anisotropy at room temperature, and when the temperature of said readout magnetic film reaches a predetermined temperature by a readout light irradiation, the readout magnetic film is a perpendicular magnetic anisotropy film, said predetermined temperature being set to be higher than room temperature and lower than a Curie temperature of said readout magnetic film by adjusting a composition of said readout magnetic film,
wherein said readout magnetic film is formed of a film having a compensation temperature which is equal to or higher than said predetermined temperature, said film being a perpendicular magnetic anisotropy film at about the compensation temperature, said readout magnetic film having the composition of
Gdx{FeyCo(1−y)}(1−x)
where 0.23≦x≦0.28 and 0.5≦y≦0.75,
wherein said recording means further includes a controlling magnetic film for controlling the exchange-coupling force, said controlling magnetic film being provided between said recording magnetic film and said readout magnetic film, and
wherein said controlling magnetic film has in-plane magnetic anisotropy at room temperature, thereby suppressing the exchange-coupling force between said recording magnetic film and said readout magnetic film, and said controlling magnetic film is a ferrimagnetic film having a compensation temperature which is approximately equal to said predetermined temperature, thereby when the temperature of said controlling magnetic film reaches said predetermined temperature by the readout light irradiation, the controlling magnetic film promotes the exchange-coupling force between said recording magnetic film and said readout magnetic film, whereby the information recorded in said recording magnetic film is magnetically transferred to said readout magnetic film.
2. A magneto-optical recording medium according to claim 1, wherein said controlling magnetic film is formed of a material selected from the group consisting of GdFe, GdCo, GdFeCo, TbFeCo, and DyFeCo.
a recording magnetic film for recording the information, said recording magnetic film being formed of a perpendicular magnetic anisotropy film;
a readout magnetic film for optically reading out the information, said readout magnetic film being capable of being magnetically coupled with said recording magnetic film by an exchange-coupling force; and
a controlling magnetic film, provided between said recording magnetic film and said readout magnetic film, for controlling the exchange-coupling force, and
wherein said readout magnetic film has in-plane magnetic anisotropy at room temperature, and is a perpendicular magnetic anisotropy film when the temperature of said readout magnetic film is increased to a predetermined temperature by a readout light irradiation, said predetermined temperature being set to be higher than room temperature and lower than a Curie temperature of said readout magnetic film by adjusting a composition of said readout magnetic film,
wherein said readout magnetic film is formed of a film having a compensation temperature which is equal to or higher than said predetermined temperature, said film being an in-plane magnetic anisotropy film at room temperature and a perpendicular magnetic anisotropy film at about the compensation temperature, said readout magnetic film having the composition of
where 0.23≦x≦0.28 and 0.5≦y≦0.75, and
wherein said controlling magnetic film has a compensation temperature which is approximately equal to said predetermined temperature and a Curie temperature which is set in the range from said predetermined temperature to a temperature lower than a temperature obtainable by irradiating a readout light upon said readout magnetic film, whereby the information recorded in said recording magnetic film is magnetically transferred to said readout magnetic film via a region having a temperature in the range of said predetermined temperature to the Curie temperature.
4. A magneto-optical recording medium according to claim 3, wherein said controlling magnetic film is formed of a material selected from the group consisting of TbFeCo, DyFeCo, and HoFeCo.
US08160976 1992-12-01 1993-11-30 Magneto-optical recording medium Expired - Fee Related US6399227B1 (en)
JP4-321613 1992-12-01
JP32161392A JP3092363B2 (en) 1992-12-01 1992-12-01 Magneto-optical recording medium
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US09612896 Division US6521357B1 (en) 1992-12-01 2000-07-10 Magneto-optical recording medium
US10121780 Division US6811889B2 (en) 1992-12-01 2002-04-12 Magneto-optical recording medium having a GDFECO readout magnetic film
US6399227B1 true US6399227B1 (en) 2002-06-04
ID=18134483
US08160976 Expired - Fee Related US6399227B1 (en) 1992-12-01 1993-11-30 Magneto-optical recording medium
US09612896 Expired - Fee Related US6521357B1 (en) 1992-12-01 2000-07-10 Magneto-optical recording medium
US10121780 Expired - Fee Related US6811889B2 (en) 1992-12-01 2002-04-12 Magneto-optical recording medium having a GDFECO readout magnetic film
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