Thermally - assisted magnetic recording disk with recording layer exchange- coupled to antiferromagnetic-to-ferromagnetic switching layer

Abstract

A magnetic recording medium for thermally-assisted recording is a bilayer of a high-coercivity, high-anisotropy ferromagnetic material like FePt and a switching material like FeRh or Fe(RhM) (where M is Ir, Pt, Ru, Re or Os) that exhibits a switch from antiferromagnetic to ferromagnetic at a transition temperature less than the Curie temperature of the high-coercivity material. The high-coercivity recording layer and the switching layer are exchange coupled ferromagnetically when the switching layer is in its ferromagnetic state. To write data the bilayer medium is heated above the transition temperature of the switching layer. When the switching layer becomes ferromagnetic, the total magnetization of the bilayer is increased, and consequently the switching field required to reverse a magnetized bit is decreased without lowering the anisotropy of the recording layer. The magnetic bit pattern is recorded in both the recording layer and the switching layer. When the media is cooled to below the transition temperature of the switching layer, the switching layer becomes antiferromagnetic and the bit pattern remains in the high-anisotropy recording layer.

What is claimed is:  
     
         1 . A thermally-assisted magnetic recording disk comprising: 
 a substrate;    an antiferromagnetic-to-ferromagnetic switching layer of FeRh on the substrate and having an antiferromagnetic-to-ferromagnetic transition temperature; and    a ferromagnetic recording layer on the substrate and in contact with the switching layer and having a Curie temperature greater than the antiferromagnetic-to-ferromagnetic transition temperature of the switching layer, the switching layer and recording layer being exchange-coupled ferromagnetically when the switching layer is in its ferromagnetic state.    
     
     
         2 . The disk of  claim 1  wherein the FeRh comprises Fe(RhM), where M is an element selected from the group consisting of Ir, Pt, Ru, Re and Os.  
     
     
         3 . The disk of  claim 2  wherein the Fe(RhM) is Fe x (Rh 100-y M y ) 100-x , where (0≦y≦15) and (40≦x≦55).  
     
     
         4 . The disk of  claim 1  wherein the recording layer is formed on top of the switching layer.  
     
     
         5 . The disk of  claim 4  further comprising a seed layer between the substrate and the switching layer.  
     
     
         6 . The disk of  claim 1  further comprising a protective overcoat formed over the recording layer.  
     
     
         7 . The disk of  claim 1  wherein the recording layer has substantially perpendicular magnetic anisotropy.  
     
     
         8 . The disk of  claim 1  wherein the recording layer has substantially horizontal magnetic anisotropy.  
     
     
         9 . The disk of  claim 1  wherein the substrate is glass.  
     
     
         10 . A thermally-assisted magnetic recording disk comprising: 
 a substrate;    a layer of antiferromagnetic-to-ferromagnetic switching material on the substrate, the switching material having an antiferromagnetic-to-ferromagnetic transition temperature and comprising Fe x (Rh 100-y M y ) 100-x , where (0≦y≦15) and (40≦x≦55), and M is an element selected from the group consisting of Ir, Pt, Ru, Re and Os;    a layer of ferromagnetic recording material formed on and in contact with the switching layer and having a Curie temperature greater than the antiferromagnetic-to-ferromagnetic transition temperature of the switching layer, the switching layer and recording layer being exchange-coupled ferromagnetically when the switching layer is in its ferromagnetic state; and    a protective overcoat formed on the recording layer.