Magneto-optic recording medium and apparatus
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsYoshiyuki Nakaki, Takashi Tokunaga, Tatsuya Fukami, Motohisa Taguchi, Kazuhiko Tsutsumi
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Abstract
This invention relates to a multi-layer magneto-optic recording medium having an information recording layer and an initializing layer that can be overwritten by light modulation, and in which adjacent layers, including auxiliary layers provided for more efficient transfer from the initializing layer to the recording layer, are coupled by an exchange force. This structure enables high-density, high-speed recording of audio information, visual information, and computer data.
Claims20
A magneto-optic recording medium comprising a first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided on this first magnetic layer and coupled to said first magnetic layer by an exchange force, and a third magnetic layer provided on this second magnetic layer and coupled to said second magnetic layer by an exchange force, wherein the following relationships are satisfied
- Tc1<Tc2<Tc3
- where, Tc1:
- Curie temperature of first magnetic layer
- Tc2:
- Curie temperature of second magnetic layer
- Tc3:
- Curie temperature of third magnetic layer,
- the following relationships are additionally satisfied at room temperature
- Hc1>Hw1(2) and Hc3>Hw3(2),
- and there exists a temperature between room temperature and Tc1 at which the following relationship is satisfied
- Hc2<Hw2(3)-Hw2(1),
- where, Hc1:
- coercivity of first magnetic layer
- Hc2:
- coercivity of second magnetic layer
- Hc3:
- coercivity of third magnetic layer
- Hwi(j):
- reversal field shift in i-th layer due to exchange coupling force between j-th layer and i-th layer.
A magneto-optic recording medium comprising:
- a first magnetic layer having perpendicular magnetic anisotropy;
- a second magnetic layer provided on this first magnetic layer and coupled to said first magnetic layer by an exchange force;
- a third magnetic layer provided on this second magnetic layer and coupled to said second magnetic layer by an exchange force;
- and
- a fourth magnetic layer provided on this third magnetic layer and coupled to said third magnetic layer by an exchange force;
- wherein the following relationships are satisfied:
- Tc1<Tc2, Tc3<Tc2, Tc1<Tc4, and Tc3<Tc4,
- where, Tc1:
- Curie temperature of first magnetic layer
- Tc2:
- Curie temperature of second magnetic layer
- Tc3:
- Curie temperature of third magnetic layer
- Tc4:
- Curie temperature of fourth magnetic layer;
- and
- the magnetization of said first magnetic layer is not reversed due to the reversal of the magnetization of said second magnetic layer at room temperature;
- wherein the following relationships are additionally satisfied at room temperature
- Hc1>Hw1(2) and Hc4>Hw4(3),
- and there exists a temperature between room temperature and Tc1 or Tc3, whichever is lower, at which the following relationships are satisfied
- Hc2<Hw2(3)-Hw2(1) and Hc3<Hw3(4)-Hw3(2),
- where, Hc1:
- coercivity of first magnetic layer
- Hc2:
- coercivity of second magnetic layer
- Hc3:
- coercivity of third magnetic layer
- Hc4:
- coercivity of fourth magnetic layer
- Hwi(j):
- reversal field shift in i-th layer due to exchange coupling force between j-th layer and i-th layer.
A magneto-optic recording medium comprising a first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided on this first magnetic layer and coupled to said first magnetic layer by an exchange force, and a third magnetic layer provided on this second magnetic layer and coupled to said second magnetic layer by an exchange force, wherein the following relationships are satisfied
- Tc1<Tc2 and Tc3<Tc2,
- where, Tc1:
- Curie temperature of first magnetic layer
- Tc2:
- Curie temperature of second magnetic layer
- Tc3:
- Curie temperature of third magnetic layer,
- the following relationships are additionally satisfied at room temperature
- Hc1>Hw1(2) and Hc3>
- Hw3(2),
- and there exists a temperature between room temperature and Tc3 at which the following relationship is satisfied
- Hc2<Hw2(3)-Hw2(1),
- where, Hc1:
- coercivity of the first magnetic layer
- Hc2:
- coercivity of the second magnetic layer
- Hc3:
- coercivity of the third magnetic layer
- Hwi(j):
- reversal field shift in i-th layer due to exchange coupling force between j-th layer and i-th layer.
Dependencies are inferred from the claim text.