Magneto-optical recording medium, manufacturing method thereof and magneto-optical data recording and playback device

Abstract

This invention relates to magneto-optical recording media such as magneto-optical disks and cards, manufacturing methods of the medium and a magneto-optical recording and playback device to record and play back data using the magnetic-optical recording media. The magneto-optical recording medium has a recording layer and a reflective layer on a substrate, and the recording layer has a layered structure in which at least on spinel ferrite (or rutile-type oxide or hematite) layer and at least one garnet ferrite layer are piled together. The manufacturing method comprises the steps of heat treatment after the formation of the recording layer. In the magneto-optical recording and playback device to record and playback data, the wavelength of light for recording data is different from that for reading data, which is preferable for a magneto-optical recording medium comprising a garnet ferrite layer.

1 - 18 . (canceled).  
     
     
         19 . A magneto-optical recording medium having a recording layer and a reflective layer on a substrate, the recording layer comprising: 
 a garnet ferrite recording layer; and    at least one underlayer for the garnet ferrite recording layer selected from the group consisting of a spinel ferrite layer, rutile-type oxide layer and a hematite layer, wherein the underlayer is formed on the substrate or the reflective layer;    the garnet ferrite recording layer is formed adjacent to the underlayer after the formation of the underlayer; and    the recording layer is heat-treated after the formation of the garnet ferrite layer at a temperature of 500 to 700° C., thereby reducing the internal compressive stress of the garnet ferrite layer by the tensile stress provided from the underlayer.    
     
     
         20 . A magneto-optical recording medium according to  claim 19 , wherein said recording layer has tracks on which data are recorded, and said recording layer is formed at least on the tracks.  
     
     
         21 . A magneto-optical recording medium according to  claim 19 , wherein said recording layer is located between said substrate and said reflective layer.  
     
     
         22 . A magneto-optical recording medium according to  claim 19 , wherein said reflective layer is located between said substrate and said recording layer.  
     
     
         23 . A magneto-optical recording medium according to  claim 19 , wherein the thickness of said garnet ferrite layer is 40 to 400 nm.  
     
     
         24 . A magneto-optical recording medium according to  claim 19 , wherein the thickness of said underlayer is 10 to 100 nm.  
     
     
         25 . A magneto-optical recording medium according to  claim 19 , wherein said recording layer has a multi-layered structure in which a plurality of garnet ferrite layers and a plurality of spinel ferrite layers, rutile-type oxide layers or hematite layers are layered.  
     
     
         26 . A magneto-optical recording medium according to  claim 25 , wherein the thickness of said recording layer is 40 to 1000 nm.  
     
     
         27 . A magneto-optical recording medium according to  claim 19 , wherein grooves are formed on the surface of at least one of said substrate, said reflective layer, and said recording layer.  
     
     
         28 . A magneto-optical recording medium according to  claim 19 , wherein loads are attached to the surface of at least one of said substrate, said reflective layer, and said recording layer.  
     
     
         29 . A magneto-optical recording medium according to  claim 19 , wherein a transparent layer is formed on the surface of said recording layer or said reflective layer.  
     
     
         30 . A magneto-optical recording medium according to  claim 19 , wherein grooves are formed on the surface of said transparent layer.