US 5,705,286 A · Magneto-optical recording medium

Abstract

A magneto-optical recording medium has an exchange-coupled triplilayer film wherein a readout layer which has in-plane magnetization at room temperature, and in which a transition occurs from in-plane magnetization to perpendicular magnetization when temperature thereof is raised above T.sub.1, an intermediate layer which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained from room temperature to Curie temperature T.sub.3, and a recording layer which has perpendicular magnetization at room temperature, the perpendicular magnetization been maintained from room temperature to Curie temperature T.sub.2 which are laminated in this order, and the temperatures T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality: T.sub.1 <T.sub.3 <T.sub.2. In the above arrangement, among bits recorded on the recording layer, only the recorded bit which satisfy the following conditions is reproduced: the recorded bit in an area irradiated with a light beam and in an area having a temperature above T.sub.1, and outside an area having a temperature above T.sub.3. Accordingly, the recorded bits with a size significantly smaller than the area irradiated with the light beam can be reproduced, thereby significantly improving the recording density.

Claims56

Dependent claims

A magneto-optical recording medium, comprising:

a substrate which is transmissive to laser light;
a magnetic film formed on said substrate, said magnetic film including:
a readout layer which has in-plane magnetization at room temperature, and in which a transition occurs in a portion subjected to a temperature rise to above a first temperature T.sub.1 from in-plane magnetization to perpendicular magnetization when temperature of said portion is raised above T.sub.1 ;
a recording layer having a Curie temperature of a second temperature T.sub.2 for recording thereon information magneto-optically, which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained in a temperature range from room temperature to Curie temperature T.sub.2 ;
and
an intermediate layer formed between said readout layer and said recording layer,
said intermediate layer structured so that an exchange coupling force exerted between said recording layer and said readout layer passes through said intermediate layer in an area having a temperature below a third temperature T.sub.3, and said exchange coupling force is masked by said intermediate layer in an area having a temperature above T.sub.3, and
wherein said temperatures T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality:
T.sub.1 <T.sub.3 <T.sub.2.
2.

7 more elements

A magnetic-optical recording medium comprising:

a transparent substrate, transparent to laser light;
a first transparent dielectric layer, transparent to laser light, formed on said transparent substrate, for enhancing a magnetic Kerr rotation angle, said first transparent dielectric layer having a thickness of a value obtained by dividing a quarter of a wavelength of a reproducing laser light beam by a reflective index of said first transparent dielectric layer;
a readout layer formed on said first transparent dielectric layer, said readout layer having in-plane magnetization at room temperature, and in which a transition occurs in a portion subjected to a temperature rise above a first temperature T.sub.1 from in-plane magnetization to perpendicular magnetization when the temperature of said portion is raise above T.sub.1 ;
an intermediate layer, having a Curie temperature of a third temperature T.sub.3 and being formed on said readout layer, which has in-plane magnetization at room temperature, the in-plane magnetization being maintained in a temperature range of room temperature to Curie temperature T.sub.3 ;
a recording layer, having a Curie temperature of a second temperature T.sub.2 and being formed on said intermediate layer, for recording thereon information magneto-optically, which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained in a temperature range of room temperature to Curie temperature T.sub.2 ;
a second transparent dielectric layer, transparent to light, formed on said recording layer, for protecting said recording layer;
an overcoat layer formed on said second transparent dielectric layer, for protecting said second transparent dielectric layer;
and
wherein said temperature T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality:
T.sub.1 <T.sub.3 <T.sub.2.
52.

8 more elements

A magneto-optical recording medium comprising:

a transparent substrate, transparent to laser light;
a first transparent dielectric layer, transparent to laser light, formed on said transparent substrate, for enhancing a magnetic Kerr rotation angle, said first transparent dielectric layer having a thickness of a value obtained by dividing a quarter of a wavelength of a reproducing laser light beam by a reflective index of said first transparent dielectric layer;
a readout layer formed on said first transparent dielectric layer, said readout layer has in-plane magnetization at room temperature, and in which a transition occurs in a portion subjected to a temperature rise above a first temperature T.sub.1 from in-plane magnetization to perpendicular magnetization when the temperature of said portion is raise above T.sub.1 ;
an intermediate layer formed on said readout layer, which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained in a temperature range of room temperature to Curie temperature
a recording layer, having a Curie temperature of a second temperature T.sub.2, formed on said intermediate layer, for recording thereon information magneto-optically, which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained in a temperature range of room temperature to Curie temperature T.sub.2 ;
a second transparent dielectric layer, transparent to laser light, formed on said recording layer, for protecting said recording layer;
an overcoat layer provided on said second transparent dielectric layer, for protecting said second transparent dielectric layer;
said intermediate layer structured so that an exchange coupling force exerted between said recording layer and said readout layer passes through said intermediate layer in an area having a temperature below a third temperature T.sub.3, and said exchange coupling force is masked by said intermediate layer in an area having a temperature above T.sub.3 ;
and
wherein said temperatures T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality:
T.sub.1 <T.sub.3 <T.sub.2.
54.

9 more elements

A magneto-optical recording medium comprising:

a transparent substrate, transparent to laser light;
a first transparent dielectric layer, transparent to laser light, formed on said transparent substrate, for enhancing a magnetic Kerr rotation angle, said first transparent dielectric layer having a thickness of a value obtained by dividing a quarter of a wavelength of a reproducing laser light beam by a reflective index of said first transparent dielectric layer;
a readout layer formed on said first transparent dielectric layer, said readout layer having in-plane magnetization at room temperature, and in which a transition occurs in a portion subjected to a temperature rise above a first temperature T.sub.1 from in-plane magnetization to perpendicular magnetization when the temperature of said portion is raise above T.sub.1 ;
an intermediate layer formed on said readout layer, said intermediate layer having perpendicular magnetization at room temperature, and in which a transition occurs in a portion subjected to a temperature rise above a third temperature T.sub.3 from perpendicular magnetization to in-plane magnetization when the temperature of said portion is raised above T.sub.3 ;
a recording layer, having a Curie temperature of a second temperature T.sub.2 and being formed on said intermediate layer, for recording thereon information magneto-optically, which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained in a temperature range of room temperature to the Curie temperature T.sub.2 ;
a second transparent dielectric layer, transparent to light, formed on said recording layer, for protecting said recording layer;
an overcoat layer provided on said second transparent dielectric layer, for protecting said second transparent dielectric layer;
and
wherein said temperatures T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality:
T.sub.1 <T.sub.3 <T.sub.2.
55.

8 more elements

An information reproducing system comprising a magneto-optical recording medium whereon information is recorded, and a reproducing device for reproducing information recorded on said magneto-optical recording medium,

said magneto-optical recording medium including:
a substrate which is transmissive to a laser light beam;
a magnetic film formed on said substrate, said magnetic film including:
a readout layer which has in-plane magnetization at room temperature, and in which a transition occurs in a portion subjected to a temperature rise to above a first temperature T.sub.1 from in-plane magnetization to perpendicular magnetization when temperature of said portion is raised above T.sub.1 ;
a recording layer having a Curie temperature of T.sub.2 for recording thereon information magneto-optically, which has perpendicular magnetization at room temperature, the perpendicular magnetization being maintained in a range from room temperature to Curie temperature T.sub.2 ;
and
an intermediate layer formed between said readout layer and said recording layer, said intermediate layer structured so that an exchange coupling force exerted between said recording layer and said readout layer passes through said intermediate layer in an area having a temperature below T.sub.3, and said exchange coupling force is masked by said intermediate layer in an area having a temperature above T.sub.3,
wherein said temperatures T.sub.1, T.sub.2 and T.sub.3 satisfy the following inequality:
T.sub.1 <T.sub.3 <T.sub.2, and
said magnetic film is arranged such that when the temperature of said portion is raised, the magnetization information on said recording layer is copied to said readout layer only in a portion having a temperature between T.sub.1 and T.sub.3,
said reproducing device includes means for projecting the laser light beam onto said magneto-optical recording medium so that a spot of the laser light beam is shifted relative to said magneto-optical recording medium, and
an intensity of the laser light beam projected from said reproducing device is set such that a portion of said magnetic film having a highest temperature has a temperature lower than T.sub.2 and higher than T.sub.3.

9 more elements

Dependencies are inferred from the claim text.

Magneto-optical recording medium

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Magneto-optical recording medium

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Abstract

Claims56