Magnetooptical recording medium and information recording and reproducing methods using the recording medium

Abstract

A method of recording information on and reproducing information from a magnetooptical recording medium which includes first and second magnetic layers. The method includes the step of projecting a light spot onto the medium. When reproducing information, the light spot is projected onto the medium from the side of the magnetic layer. In this method only a high temperature region of the second magnetic layer within a light spot projection portion is changed to a perpendicular magnetization film so that information recorded in the first magnetic layer is transferred to the perpendicular magnetization film of the second magnetic layer. In addition, information which is transferred to the second magnetic layer is detected by using reflected light from the medium which is subjected to the magneto-optic effect from the perpendicular magnetization film of the second magnetic layer. When recording information, a magnetic field is applied, whose magnetization direction is modulated according to information, to a light spot projection portion of the medium so the magnetization of the second magnetic layer is oriented to the direction of the applied magnetic field, and the magnetization of the second magnetic layer is transferred to the first magnetic layer to form a record bit.

What is claimed is:  
     
       1. A method of reproducing information in a magnetooptical recording medium which comprises a first magnetic layer, which has an in-plane magnetization at a first temperature range that disappears at a second temperature range that is higher than the first temperature range; a third magnetic layer having a perpendicular magnetization; a second magnetic layer, wherein the second magnetic layer is interposed between said first and third magnetic layers, has a Curie temperature higher than the temperatures of said first and third magnetic layers, and has an in-plane magnetization at the first temperature range that changes to a perpendicular magnetization at the second temperature range; and a substrate, wherein the substrate, and the first, second and third magnetic layers are disposed in the medium in this order: the substrate, the first magnetic layer, the second magnetic layer, and the third magnetic layer, said method comprising the steps of: 
       projecting a laser beam onto the substrate to create a light spot region;  
       changing only a high-temperature area in a light spot region of the first and second magnetic layers to a perpendicular magnetization film so that information recorded in the third magnetic layer is transferred through the second magnetic layer to the perpendicular magnetization film of the first magnetic layer; and  
       detecting the information transferred to the first magnetic layer by using reflected light from the medium which is subjected to a magneto-optic effect of the perpendicular magnetization film of the first magnetic layer.  
     
     
       2. A method of recording information in a magnetooptical recording medium which comprises a first magnetic layer being an in-plane magnetization film at a first temperature range and a perpendicular magnetization film at a second temperature range that is higher than the first temperature range, a second magnetic layer composed of a perpendicular magnetization film at both the first temperature range and the second temperature range and storing information, and a substrate, wherein the substrate, and the first and second magnetic layers are disposed in the medium in this order: the substrate, the first magnetic layer, and the second magnetic layer, said method comprising the steps of: 
       projecting a laser beam onto the substrate to create a light spot region;  
       applying a magnetic field, wherein the magnetization direction of the magnetic field is modulated according to information, to a light spot region of the substrate so that magnetization of the first magnetic layer is oriented to the direction of the applied magnetic field; and  
       transferring the magnetization of the first magnetic layer to the second magnetic layer to form a record bit.  
     
     
       3. A method of recording information according to  claim 2 , further comprising the step of detecting information from the record bit at the same time as the formation of the record bit by detecting reflected light of the light spot region from the medium. 
     
     
       4. A method of recording information in a magnetooptical recording medium which comprises a first magnetic layer, which has an in-plane magnetization at a first temperature range that disappears at a second temperature range that is higher than the first temperature range; a third magnetic layer having a perpendicular magnetization; and a second magnetic layer, wherein the second magnetic layer is interposed between said first and third magnetic layers, has a Curie temperature higher than the temperatures of said first and third magnetic layers, and has an in-plane magnetization at the first temperature range that changes to a perpendicular magnetization at the second temperature range, and a substrate, wherein the substrate, and the first, second and third magnetic layers are disposed in the medium in this order: the substrate, the first magnetic layer, the second magnetic layer, and the third magnetic layer, said method comprising the steps of: 
       projecting a laser beam onto the substrate to create a light spot region; and  
       applying a magnetic field, wherein the magnetization direction of the magnetic field is modulated according to information, to a light spot region of the substrate so that a record bit is formed in the third magnetic layer.  
     
     
       5. A method of reproducing information in a magneto- optical recording medium which comprises:    
         an auxiliary layer having a Curie temperature and having an in - plane magnetization at a first temperature range that disappears at a second tamperature range higher than the first temperature range;    
       
         a recording layer having a Curie temperature and having a perpendicular magnetization;  
       
         a reproducing layer being located opposite a light incident side of the auxiliary layer, and having a Curie temperature higher than the Curie temperatures of said auxiliary and recording layers, and having in - plane magnetization at the first temperature range that changes to a perpendicular magnetization at the second temperature range; and    
       
         a substrate;  
       
       
         said method comprising the steps of:  
       
       
         projecting a laser beam onto the substrate to create a light spot region;  
       
       
         changing only a high temperature area in a light spot region of the reproducing layer to change the high temperature area of the reproducing layer to a perpendicular magnetization film and to eliminate magnetization in the high temperature area of the auxiliary layer, so that information recorded in the recording layer is transferred to the magnetization film of the reproducing layer; and  
       
         detecting the information transferred to the reproducing layer by using reflected light from the medium which is subjected to a magneto - optical effect of the perpendicular magnetization film of the reproducing layer.