Magnetic recording medium

Abstract

The magnetic recording medium of the present invention comprises: a non-magnetic substrate; a non-magnetic layer formed on one of principal surfaces of the non-magnetic substrate; and a magnetic layer formed on a principal surface of the non-magnetic layer opposite to the non-magnetic substrate. Mr and t satisfy 0.0020 μT·m≦Mr·t≦0.0150 μT·m, where Mr is the residual magnetic flux density of the magnetic layer, and t is the average thickness of the magnetic layer, L1 satisfies 2 nm≦L1≦6 nm, where L1 is the average thickness of a first mixed layer that is formed on the surface of the magnetic layer opposite to the non-magnetic layer, and L2 satisfies 0.1≦L2/t≦0.45, where L2 is the average thickness of a second mixed layer that is formed on the surface of the magnetic layer facing the non-magnetic layer.

What is claimed is: 
     
         1 . A magnetic recording medium comprising: a non-magnetic substrate; a non-magnetic layer formed on one of principal surfaces of the non-magnetic substrate; and a magnetic layer formed on a principal surface of the non-magnetic layer opposite to the non-magnetic substrate,
 wherein the magnetic layer contains a magnetic powder,   the magnetic powder is one selected from the group consisting of a hexagonal ferrite magnetic powder and a ferromagnetic metallic iron magnetic powder,   Mr and t satisfy 0.0020 μT·m≦Mr·t≦0.0150 μT·m, where Mr is the residual magnetic flux density of the magnetic layer, and t is the average thickness of the magnetic layer, L1 satisfies 2 nm≦L1≦6 nm, where L1 is the average thickness of a first mixed layer that is formed on the surface of the magnetic layer opposite to the non-magnetic layer, and   the magnetic layer has the average thickness of 20 to 100 nm.   
     
     
         2 . The magnetic recording medium according to  claim 1 , wherein L1 as the average thickness of the first mixed layer satisfies 2 nm≦L1≦4 nm, and L2 as the average thickness of the second mixed layer satisfies 0.1≦L2/t≦0.40. 
     
     
         3 . The magnetic recording medium according to  claim 1 , wherein L2 satisfies 0.1≦L2/t≦0.45, where L2 is the average thickness of a second mixed layer that is formed on the surface of the magnetic layer facing the non-magnetic layer. 
     
     
         4 . The magnetic recording medium according to  claim 1 , wherein the magnetic powder has an average particle size of 10 to 35 nm. 
     
     
         5 . The magnetic recording medium according to  claim 1 , wherein the magnetic layer has a thickness of 30 to 70 nm. 
     
     
         6 . The magnetic recording medium according to  claim 1 , wherein the magnetic layer has Ra of 1.0 nm or more and less than 2.0 nm, where Ra is centerline average roughness defined in JIS B0601. 
     
     
         7 . The magnetic recording medium according to  claim 1 , wherein the non-magnetic layer has a thickness of 0.1 to 3 μm.