Magnetic recording medium

Abstract

In a magnetic recording medium including a substrate ( 1 ) having a principal surface on which first and second magnetic layers ( 5 and 7 ) and a spacer layer ( 6 ) are at least formed, each of the first and the second magnetic layers being of a ferromagnetic material, the spacer layer being formed between the first and the second magnetic layers for inducing antiferromagnetic exchange interaction between the first and the second magnetic layers, the principal surface of the substrate is provided with concentric textures to have a predetermined surface roughness so that the spacer layer has a uniform thickness. The first magnetic layer is for controlling the antiferromagnetic exchange interaction.

What is claimed is:  
     
         1 . A magnetic recording medium comprising a substrate having a principal surface on which first and second magnetic layers and a spacer layer are at least formed, each of said first and said second magnetic layers being of a ferromagnetic material, said spacer layer being formed between said first and said second magnetic layers for inducing antiferromagnetic exchange interaction between said first and said second magnetic layers, said first magnetic layer being for controlling said antiferromagnetic exchange interaction, the principal surface of said substrate being provided with concentric textures to have a predetermined surface roughness so that said spacer layer has a uniform thickness.  
     
     
         2 . A magnetic recording medium as claimed in  claim 1 , wherein said predetermined surface roughness of the principal surface due to said concentric textures falls within a range between 1.5 nm and 10 nm, both inclusive, in a surface roughness Rmax, where Rmax is defined as a maximum height representative of a difference between a highest point and a lowest point.  
     
     
         3 . A magnetic recording medium as claimed in  claim 1 , wherein a radial pitch of said concentric textures is substantially equal to a grain size of said first and said second magnetic layers.  
     
     
         4 . A magnetic recording medium as claimed in  claim 1 , wherein the concentric textures have a radial pitch falling within a range between 0.005 μm and 0.05 μm, both inclusive.  
     
     
         5 . A magnetic recording medium as claimed in  claim 1 , wherein said substrate is a glass substrate made of glass, said concentric textures are directly formed on a surface of said glass substrate.