Magneto-optical recording medium having magnetization variable between in-plane magnetization and perpendicular magnetization

A magneto-optical recording medium comprising:

• a recording layer which is constituted of a magnetic substance where information is magneto-optically recorded and which exhibits a perpendicular direction of magnetization from room temperature T1 to a Curie temperature Tc3;
• a readout layer, which is provided on said recording layer and which is constituted of a magnetic substance composed of a rare-earth transition metal alloy, from which readout layer the information recorded in said recording layer is reproduced, the readout layer having a compensation temperature Tcomp1 and exhibiting a perpendicular direction of magnetization only from a temperature Tr1 to a temperature Tr2 and an in-plane direction of magnetization from room temperature to the temperature Tr1;
• and
• an intermediate layer which is provided between said recording layer and said readout layer and which is constituted of a magnetic substance, the intermediate layer having a compensation temperature Tcomp2, and exhibiting a perpendicular direction of magnetization only in a temperature range from a temperature Ti1 to a temperature Ti2 including the Curie temperature Tc3 therein and an in-plane direction of magnetization from room temperature to the temperature Ti1;
• wherein
• defining T3 as a temperature not lower than Ti1, not higher than Tcomp1, and not higher than Tcomp2;
• and
• defining T4 as a temperature not lower than Tc3, not lower than Tcomp1, not lower than Tcomp2, and not higher than Tr2;
• and
• defining Hc1 and Hc3 respectively as a coercive force of said readout layer and a coercive force of said recording layer, for a predetermined magnetic field Hw;
• the following conditions are satisfied;
• when a temperature of said medium is T1, Hc1<Hw and Hw<Hc3;
• when a temperature of said medium is T3, Hc3<Hw and Hw<Hc1;
• and
• when a temperature of said medium is T4, Hc1<Hw.

A method of recording and reproducing magneto-optical information using a recording medium having a recording layer, a readout layer and an intermediate layer interposed therebetween, said method comprising:

• a recording step of recording information as a magnetization pattern onto said recording layer;
• and
• a reproducing step of reproducing the information stored as the magnetization pattern recorded on the recording layer,
• wherein the recording step includes the steps of:
• applying a magnetic field Hw onto the magneto-optical recording medium;
• shining a first light beam (I), having a low light intensity, onto said magneto-optical recording medium according to recorded information, thereby making a sub-lattice magnetic moment, of a rare-earth metal of said readout layer, point in a direction of the field Hw and making a magnetization direction of said recording layer point in a predetermined direction due to an exchange-coupling force from said readout layer;
• and
• shining a second light beam (II), having a high light intensity higher than the light intensity of the first light beam (I), onto said magneto-optical recording medium according to recorded information, thereby making a sub-lattice magnetic moment, of a rare-earth metal of said readout layer, point in a direction opposite to a direction of the field Hw and making, due to an exchange-coupling force from said readout layer, a magnetization direction, of said recording layer, point in a predetermined direction opposite to the direction in which said recording layer points when the first light beam (I) is applied, and
• the reproducing step includes the step of:
• shining a third light beam (III), having a light intensity lower than the light intensity of the first light beam (I), onto said magneto-optical recording medium;
• and
• orienting a sub-lattice magnetization of said readout layer in a direction which stable for a sub-lattice magnetization of said recording layer after application of the third light beam (III).

A method of recording and reproducing magneto-optical information using a recording medium having a recording layer, a readout layer and an intermediate layer interposed therebetween, said method comprising:

• a recording step of recording information as a magnetization pattern onto said recording layer;
• and
• a reproducing step of reproducing the information stored as the magnetization pattern recorded on the recording layer,
• wherein the recording step includes the steps of:
• applying a magnetic field Hw onto the magneto-optical recording medium;
• shining a first light beam (I), having a low light intensity, onto said magneto-optical recording medium according to recorded information, thereby making a sub-lattice magnetic moment, of a rare-earth metal of said readout layer, point in a direction of the field Hw and making a magnetization direction of said recording layer point in a predetermined direction due to an exchange-coupling force from said readout layer;
• and
• shining a second light beam (II), having a high light intensity higher than the light intensity of the first light beam (I), onto said magneto-optical recording medium according to recorded information, thereby making a sub-lattice magnetic moment, of rare-earth metal of said readout layer, point in a direction opposite to a direction of the field Hw and making, due to an exchange-coupling force from said readout layer, a magnetization direction, of said recording layer, point in a predetermined direction opposite to the direction in which said recording layer points when the first light beam (I) is applied, and
• the reproducing step includes the steps of:
• shining a third light beam (III), having a light intensity lower than the light intensity of the first light beam (I) and having a distribution of light intensity in which light intensity is higher in a center of the light beam than in an area surrounding the center, onto said magneto-optical recording medium;
• and
• orienting a sub-lattice magnetization of said readout layer in a direction which is stable for a sub-lattice magnetization of said recording layer after application of the third light beam (III).