Magnetic particle, its production method, magnetic recording medium and its production method

Abstract

The present invention relates to a method of producing a magnetic particle including forming a layer containing an alloy particle that can form CuAu type or Cu 3 Au type hard magnetic order alloy phase on a support, oxidizing the layer, and annealing the layer in non-oxidizing atmosphere. The invention also relates to a method of producing a magnetic particle including producing an alloy particle that can form hard magnetic order alloy phase, oxidizing the alloy particle, and annealing the particle in non-oxidizing atmosphere, and a magnetic particle produced by the foregoing production method. Further, the invention relates to a magnetic recording medium comprising a magnetic layer containing a magnetic particle and a method of producing a magnetic recording medium including forming a layer containing an alloy that can form the foregoing hard magnetic order alloy phase, oxidizing the layer, and annealing the layer in non-oxidizing atmosphere.

What is claimed is:  
     
         1 . A method of producing a magnetic particle including producing an alloy particle that can form a CuAu type or Cu 3 Au type hard magnetic order alloy phase, oxidizing the alloy particle, and annealing the particle in a non-oxidizing atmosphere.  
     
     
         2 . A method of producing a magnetic particle according to  claim 1 , wherein the atmosphere for the annealing is a reducing atmosphere, an annealing temperature is 450° C. or lower, and a retention time is 10 minutes or shorter.  
     
     
         3 . A method of producing a magnetic particle according to  claim 1 , wherein a third element other than elements that can form the CuAu type or Cu 3 Au type hard magnetic order alloy phase, is added to the alloy particle as an alloying element.  
     
     
         4 . A magnetic particle produced by a method including producing an alloy particle that can form a CuAu type or Cu 3 Au type hard magnetic order alloy phase, oxidizing the alloy particle, and annealing the particle in a non-oxidizing atmosphere.  
     
     
         5 . A magnetic particle according to  claim 4 , wherein the atmosphere for the annealing is a reducing atmosphere, an annealing temperature is 450° C. or lower, and a retention time is 10 minutes or shorter.  
     
     
         6 . A magnetic particle according to  claim 4 , wherein a third element other than elements that can form the CuAu type or Cu 3 Au type hard magnetic order alloy phase, is added to the alloy particle as an alloying element.  
     
     
         7 . A magnetic recording medium comprising a magnetic layer containing magnetic particles produced by a method including producing alloy particles that can form a CuAu type or Cu 3 Au type hard magnetic order alloy phase, oxidizing the alloy particles, and annealing the particles in non-oxidizing atmosphere.  
     
     
         8 . A magnetic recording medium according to  claim 7 , wherein the atmosphere for the annealing is a reducing atmosphere, an annealing temperature is 450° C. or lower, and a retention time is 10 minutes or shorter.  
     
     
         9 . A magnetic recording medium according to  claim 7 , wherein a third element other than elements that can form the CuAu type or Cu 3 Au type hard magnetic order alloy phase, is added to the alloy particles as an alloying element.  
     
     
         10 . A method of producing a magnetic recording medium including forming on a support a layer containing an alloy that can form a CuAu type or Cu 3 Au type hard magnetic order alloy phase, oxidizing the layer, and annealing the layer in a non-oxidizing atmosphere.  
     
     
         11 . A method of producing a magnetic recording medium according to  claim 10 , wherein the atmosphere for the annealing is a reducing atmosphere, an annealing temperature is 450° C. or lower, and a retention time is 10 minutes or shorter.