Magnetic recording medium and magnetic storage apparatus

Abstract

A magnetic recording medium is provided with at least one exchange layer structure, and a magnetic layer formed on the exchange layer structure. The exchange layer structure includes a ferromagnetic layer, and a non-magnetic coupling layer provided on the ferromagnetic layer and under the magnetic layer. The ferromagnetic layer and the magnetic layer have antiparallel magnetizations.

What is claimed is:  
     
         1 . A magnetic recording medium comprising: 
 at least one exchange layer structure; and    a magnetic layer formed on said exchange layer structure,    said exchange layer structure comprising: 
 a ferromagnetic layer; and  
 a non-magnetic coupling layer provided on said ferromagnetic layer and under said magnetic layer,  
   said ferromagnetic layer and said magnetic layer having antiparallel magnetizations.    
     
     
         2 . The magnetic recording medium as claimed in  claim 1 , wherein said ferromagnetic layer is made of a material selected from a group consisting of Co, Ni, Fe, Ni-based alloys, Fe-based alloys, and Co-based alloys including CoCrTa, CoCrPt and CoCrPt-M, where M=B, Mo, Nb, Ta, W or alloys thereof.  
     
     
         3 . The magnetic recording medium as claimed in  claim 1 , wherein said ferromagnetic layer has a thickness in a range of 2 to 10 nm.  
     
     
         4 . The magnetic recording medium as claimed in  claim 1 , wherein said non-magnetic coupling layer is made of a material selected from a group of Ru, Rh, Ir, Ru-based alloys, Rh-based alloys, and Ir-based alloys.  
     
     
         5 . The magnetic recording medium as claimed in  claim 1 , wherein said non-magnetic coupling layer has a thickness in a range of 0.4 to 0.9 nm.  
     
     
         6 . The magnetic recording medium as claimed in  claim 1 , wherein said magnetic layer is made of a material selected from a group of Co, and Co-based alloys including CoCrTa, CoCrPt and CoCrPtM, where M=B, Mo, Nb, Ta, W or alloys thereof.  
     
     
         7 . The magnetic recording medium as claimed in  claim 1 , which further comprises: 
 a substrate; and    an underlayer provided above said substrate, said exchange layer structure being provided above said underlayer.    
     
     
         8 . The magnetic recording medium as claimed in  claim 7 , which further comprises: 
 a non-magnetic intermediate layer interposed between said underlayer and said exchange layer structure,    said non-magnetic intermediate layer having a hcp structure alloy selected from a group of CoCr-M, where M=B, Mo, Nb, Ta, W or alloys thereof, and having a thickness in a range of 1 to 5 nm.    
     
     
         9 . The magnetic recording medium as claimed in  claim 8 , which further comprises: 
 a NiP layer interposed between said substrate and said underlayer, said NiP layer being mechanically textured or oxidized.    
     
     
         10 . The magnetic recording medium as claimed in  claim 7 , wherein said underlayer is made of a B2 structure alloy selected from a group of NiAl and FeAl.  
     
     
         11 . The magnetic recording medium as claimed in  claim 1 , which comprises at least a first exchange layer structure and a second exchange layer structure interposed between said first exchange layer structure and said magnetic layer, wherein a ferromagnetic layer of said second exchange layer structure has a magnetic anisotropy lower than that of a ferromagnetic layer of said first exchange layer structure, and magnetizations of the ferromagnetic layers of said first and second exchange layer structures are antiparallel.  
     
     
         12 . The magnetic recording medium as claimed in  claim 1 , which comprises at least a first exchange layer structure and a second exchange layer structure interposed between said first exchange layer structure and said magnetic layer, wherein a product of a remanent magnetization and thickness of a ferromagnetic layer of said second exchange layer structure is smaller than that of a ferromagnetic layer of said first exchange layer structure, and magnetizations of the ferromagnetic layers of said first and second exchange layer structures are antiparallel.  
     
     
         13 . A magnetic storage apparatus comprising: 
 at least one magnetic recording medium including at least one exchange layer structure, and a magnetic layer formed on said exchange layer structure; and    at least one head recording information on and/or reproducing information from the recording medium,    said exchange layer structure comprising: 
 a ferromagnetic layer; and  
 a non-magnetic coupling layer provided on said ferromagnetic layer and under said magnetic layer,  
   said ferromagnetic layer and said magnetic layer having antiparallel magnetizations.    
     
     
         14 . The magnetic storage apparatus as claimed in  claim 13 , wherein said ferromagnetic layer is made of a material selected from a group consisting of Co, Ni, Fe, Ni-based alloys, Fe-based alloys, and Co-based alloys including CoCrTa, CoCrPt and CoCrPt-M, where M=B, Mo, Nb, Ta, W or alloys thereof.  
     
     
         15 . The magnetic storage apparatus as claimed in  claim 13 , wherein said ferromagnetic layer has a thickness in a range of 2 to 10 nm.  
     
     
         16 . The magnetic storage apparatus as claimed in  claim 13 , wherein said non-magnetic coupling layer is made of a material selected from a group of Ru, Rh, Ir, Ru-based alloys, Rh-based alloys, and Ir-based alloys.  
     
     
         17 . The magnetic storage apparatus as claimed in  claim 13 , wherein said non-magnetic coupling layer has a thickness in a range of 0.4 to 0.9 nm.  
     
     
         18 . The magnetic storage apparatus as claimed in  claim 13 , wherein said magnetic layer is made of a material selected from a group of Co, and Co-based alloys including CoCrTa, CoCrPt and CoCrPtM, where M=B, Mo, Nb, Ta, W or alloys thereof.