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US 5,639,567 AGranted
Exchange-coupled direct overwrite magneto-optic recording media
AssigneeImation Corp.
InventorWilliam A. Challener, IV
Life of this patent
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Abstract
A magneto-optic recording medium for use with a recording system including a laser beam operable at at least two different energy levels and magnetic field source(s) for generating two different magnetic fields. The medium includes a substrate and at least two layers: a magneto-optical storage layer and a magnetic biasing layer. The storage layer maintains areas of selected magnetic orientation and is made of a rare earth transition metal alloy, such as terbium-iron-cobalt. The magnetic biasing layer is magnetically exchange-coupled to the storage layer and is made of a rare earth transition metal alloy, such as dysprosium-terbium-iron-cobalt. The Curie temperature of the storage layer is greater than that of the bias layer.
Claims27
A magneto-optic recording medium for use with a recording system including a laser operable at at least two different energy levels, the medium comprising a substrate and a plurality of layers supported thereon, the layers comprising:
- a magneto-optical storage layer, for maintaining areas of selected magnetic orientation, comprising a rare earth transition metal alloy, the storage layer having a first magnetic moment, a first compensation temperature, T.sub.compstor, and a first Curie temperature, T.sub.curstor ;
- and
- a magnetic biasing layer, magnetically exchange-coupled to the storage layer, comprising a rare earth transition metal alloy, the biasing layer having a second magnetic moment, a second compensation temperature, T.sub.compbias, and a second Curie temperature, T.sub.curbias, wherein T.sub.Curstor >T.sub.Curbias ;
- such that a recorded bit in the layers at any temperature less than T.sub.Curbias exists in one of four magnetic states:
- a first state in which the storage layer is magnetized "up" and the bias layer is magnetized so that there is no horizontal domain wall between the layers;
- a second state in which the storage layer is magnetized "up" and the bias layer is magnetized so that there is a horizontal domain wall between the layers;
- a third state in which the storage layer is magnetized "down" and the bias layer is magnetized so that there is no horizontal domain wall between the layers;
- and
- a fourth state in which the storage layer is magnetized "down" and the bias layer is magnetized so that there is a horizontal domain wall between the layers;
- wherein:
- at ambient temperature, T.sub.a, and no applied magnetic field, the fourth state is stable;
- at T.sub.a in the presence of a first magnetic field applied in a direction opposite to the second magnetic moment, the third state is convened into the fourth state;
- at a first recording temperature, T.sub.1, wherein T.sub.a <T.sub.1 <T.sub.Curbias, in the presence of a second magnetic field applied in the direction of the first magnetic moment, the fourth state is converted to the first state and the second state is converted to the third state;
- and
- at a second recording temperature, T.sub.2, where T.sub.2 >T.sub.1, in the presence of a second magnetic field applied in the direction opposite the first magnetic moment, the first magnetic moment reverses its direction.
12 more elements
A magneto-optic recording medium comprising a substrate and a plurality of layers supported thereon, the layers comprising:
- a magneto-optic storage layer comprising Tb, Fe, and Co, having a Curie temperature, T.sub.Curstor ;
- a magnetic biasing layer, magnetically exchange-coupled to the storage layer, comprising Dy, Tb, Fe, and Co, having a Curie temperature T.sub.curbias, wherein T.sub.curstor >T.sub.curbias.
A magneto-optic recording system comprising:
- a laser operable at at least at two different energy levels;
- means for producing a first initializing magnetic field and a second applied recording magnetic field;
- a magneto-optic recording medium comprising a substrate and a plurality of layers supported thereon, the layers comprising:
- a magneto-optical storage layer, for maintaining areas of selected magnetic orientation, comprising a rare earth transition metal alloy, the storage layer having a first magnetic moment, a first compensation temperature, T.sub.compstor, and a first Curie temperature, T.sub.Curstor ;
- and
- a magnetic biasing layer, magnetically exchange-coupled to the storage layer, comprising a rare earth transition metal alloy, the biasing layer having a second magnetic moment, a second compensation temperature, T.sub.compbias, and a second Curie temperature, T.sub.Curbibas, wherein T.sub.Curstor >T.sub.Curbias ;
- such that a recorded bit in the layers at any temperature less than T.sub.Curbias exists in one of four magnetic states:
- a first state in which the storage layer is magnetized "up" and the bias layer is magnetized so that there is no horizontal domain wall between the layers;
- a second state in which the storage layer is magnetized "up" and the bias layer is magnetized so that there is a horizontal domain wall between the layers;
- a third state in which the storage layer is magnetized "down" and the bias layer is magnetized so that there is no horizontal domain wall between the layers;
- and
- a fourth state in which the storage layer is magnetized "down" and the bias layer is magnetized so that there is a horizontal domain wall between the layers;
- wherein:
- at ambient temperature, T.sub.a, and no applied magnetic field, the fourth state is stable;
- at T.sub.a in the presence of a first magnetic field applied in a direction opposite to the second magnetic moment, the third state is converted into the fourth state;
- at a first recording temperature, T.sub.1, wherein T.sub.a <T.sub.1 <T.sub.Curbias in the presence of a second magnetic field applied in the direction of the first magnetic moment, the fourth state is converted to the first state and the second state is converted to the third state;
- and
- at a second recording temperature, T.sub.2, where T.sub.2 >T.sub.1, in the presence of a second magnetic field applied in the direction opposite the first magnetic moment, the first magnetic moment reverses its direction.
15 more elements
A magneto-optic recording medium for use with a recording system comprised of a laser beam operable at at least two different energy levels, the medium comprising a substrate and a plurality of layers supported thereon, the layers comprising:
- a magneto-optical storage layer, for maintaining areas of selected magnetic orientation, comprising a rare earth transition metal alloy, the storage layer having a first magnetic moment, a first compensation temperature, T.sub.compstor, and a first Curie temperature, T.sub.Curstor ;
- and
- a magnetic biasing layer, magnetically exchange-coupled to the storage layer, comprising a rare earth transition metal alloy, the biasing layer having a second magnetic moment, a second compensation temperature, T.sub.compbias, and a second Curie temperature, T.sub.Curbias, wherein T.sub.Curstor is within the range of 40.degree. to 60.degree. C. greater than T.sub.Curbias ;
- such that a recorded bit in the layers at any temperature less than T.sub.Curbias exists in one of four magnetic states:
- a first state in which the storage layer is magnetized "up" and the bias layer is magnetized so that there is no horizontal domain wall between the layers;
- a second state in which the storage layer is magnetized "up" and the bias layer is magnetized so that there is a horizontal domain wall between the layers;
- a third state in which the storage layer is magnetized "down" and the bias layer is magnetized so that there is no horizontal domain wall between the layers;
- and
- a fourth state in which the storage layer is magnetized "down" and the bias layer is magnetized so that there is a horizontal domain wall between the layers;
- wherein:
- at ambient temperature, T.sub.a, and no applied magnetic field, the fourth state is stable;
- at T.sub.a in the presence of a first magnetic field applied in a direction opposite to the second magnetic moment, the third state is converted into the fourth state;
- at a first recording temperature, T.sub.1, wherein T.sub.a <T.sub.1 <T.sub.Courbias, in the presence of a second magnetic field applied in the direction of the first magnetic moment, the fourth state is convened to the first state and the second state is convened to the third state;
- and
- at a second recording temperature, T.sub.2, where T.sub.2 >T.sub.1, in the presence of a second magnetic field applied in the direction opposite the first magnetic moment, the first magnetic moment reverses its direction.
12 more elements
Dependencies are inferred from the claim text.