Perpendicular magnetic recording medium and process of production thereof

Abstract

A perpendicular magnetic recording medium, which has a low level of recording noise and sufficiently large perpendicular magnetic anisotropy energy relative to demagnetizing field energy, includes a substrate and a multi-layered magnetic film. The multi-layered magnetic film is composed of ferromagnetic metal layers of Co alloy containing at least Cr and non-magnetic metal layers of Pd alloy, each one layer of which are laminated alternately on top of one layer of the other. The ferromagnetic metal layers and the non-magnetic metal layers have a thickness of d 1 and d 2 , respectively, with the ratio of d 1 /d 2 being in the range of 1.5 to 4.0. This specific layer structure reduces the magnetic exchange interaction between magnetic particles in the multi-layered magnetic film. Therefore, the perpendicular magnetic recording medium is stable against thermal disturbance and has a low level of recording noise.

1 . A process for producing a perpendicular magnetic recording medium, said process comprising a step of forming an underlying layer on a substrate, a step of forming on said underlying layer an initial layer of Co alloy containing Cr or Cu, a step of forming on said initial layer a multi-layered magnetic film composed of non-magnetic metal layers containing Pd and ferromagnetic metal layers containing Co which are laminated alternately on top of the other, a step of heat treatment at a temperature higher than 350° C. which is performed after said multi-layered magnetic film has been formed, and a step of forming a carbon protective film on said multi-layered magnetic film.  
     
     
         2 . A process for producing a perpendicular magnetic recording medium according to  claim 1 , 
 wherein said ferromagnetic metal layers contain less than 20 at % of Cr.    
     
     
         3 . A process for producing a perpendicular magnetic recording medium according to  claim 1 , 
 wherein said ferromagnetic metal layers contain mores than 12 at % of Cr.    
     
     
         4 . A process for producing a perpendicular magnetic recording medium according to  claim 1 , 
 wherein said initial layer of Co alloy contain more than 30 at % of Cr or Cu.