Perpendicular magnetic recording medium with grain boundary controlling layers

Abstract

In one embodiment, a perpendicular magnetic recording medium includes an oxide recording layer including an oxide and a non-oxide recording layer which does not contain an oxide positioned above the oxide recording layer. The oxide recording layer includes a first recording layer, a second recording layer, a third recording layer, and a fourth recording layer. Also, an oxide concentration of the first recording layer is greater than an oxide concentration of the second recording layer, an oxide concentration of the third recording layer is greater than an oxide concentration of the fourth recording layer, and the oxide concentration of the third recording layer is greater than the oxide concentration of the second recording layer.

What is claimed is: 
     
         1 . A perpendicular magnetic recording medium, comprising:
 an oxide recording layer comprising an oxide;   a non-oxide recording layer which does not contain an oxide positioned above the oxide recording layer;   wherein the oxide recording layer comprises:
 a first recording layer; 
 a second recording layer; 
 a third recording layer; and 
 a fourth recording layer, 
   wherein an oxide concentration of the first recording layer is greater than an oxide concentration of the second recording layer,   wherein an oxide concentration of the third recording layer is greater than an oxide concentration of the fourth recording layer, and   wherein the oxide concentration of the third recording layer is greater than the oxide concentration of the second recording layer.   
     
     
         2 . The perpendicular magnetic recording medium as recited in  claim 1 , wherein a thickness of the first recording layer is between about 0.5 nm and about 3.0 nm, and wherein a thickness of the third recording layer is between about 1.0 nm and about 4.0 nm. 
     
     
         3 . The perpendicular magnetic recording medium as recited in  claim 1 , wherein a magnetic anisotropy energy of the fourth recording layer is smaller than a magnetic anisotropy energy of the second recording layer. 
     
     
         4 . The perpendicular magnetic recording medium as recited in  claim 3 , wherein a saturation magnetization of the third recording layer is lower than a saturation magnetization of the fourth recording layer. 
     
     
         5 . The perpendicular magnetic recording medium as recited in  claim 1 , wherein a ratio of concentrations of Pt and Cr in the fourth recording layer (Pt concentration/Cr concentration) is smaller than a ratio of concentrations of Pt and Cr in the second recording layer. 
     
     
         6 . The perpendicular magnetic recording medium as recited in  claim 5 , wherein a saturation magnetization of the third recording layer is lower than a saturation magnetization of the fourth recording layer. 
     
     
         7 . The perpendicular magnetic recording medium as recited in  claim 5 , wherein a Cr concentration in the third recording layer is greater than a Cr concentration in the fourth recording layer. 
     
     
         8 . The perpendicular magnetic recording medium as recited in  claim 1 , wherein the fourth recording layer has a structural characteristic of being formed with a lower sputter gas pressure than a sputter gas pressure used when the first, second, and third recording layers are formed. 
     
     
         9 . A magnetic data storage system, comprising:
 at least one magnetic head;   a perpendicular magnetic recording medium as recited in  claim 1 ;   a drive mechanism for passing the magnetic recording medium over the at least one magnetic head; and   a controller electrically coupled to the at least one magnetic head for controlling operation of the at least one magnetic head.   
     
     
         10 . A method, comprising:
 forming a first oxide recording layer comprising an oxide above a substrate;   forming a second oxide recording layer on the first oxide recording layer;   forming a third oxide recording layer on the second oxide recording layer;   forming a fourth oxide recording layer on the third oxide recording layer; and   forming a non-oxide recording layer which does not contain an oxide on the fourth oxide recording layer,   wherein an oxide concentration of the first oxide recording layer is greater than an oxide concentration of the second oxide recording layer,   wherein an oxide concentration of the third oxide recording layer is greater than an oxide concentration of the fourth oxide recording layer, and   wherein the oxide concentration of the third oxide recording layer is greater than the oxide concentration of the second oxide recording layer.   
     
     
         11 . The method as recited in  claim 10 ,
 wherein a grain boundary width of the first oxide recording layer increases in a direction perpendicular to a plane of formation of the first oxide recording layer from a lowermost portion of the first oxide recording layer toward a medium surface,   wherein a grain boundary width of the third oxide recording layer increases in a direction perpendicular to a plane of formation of the third oxide recording layer toward the medium surface,   wherein a grain boundary width of the second oxide recording layer decreases, and   wherein a grain boundary width of the fourth oxide recording layer decreases.   
     
     
         12 . The method as recited in  claim 10 , further comprising:
 forming an adhesion layer above the substrate;   forming a soft magnetic underlayer above the adhesion layer;   forming a seed layer above the soft magnetic underlayer; and   forming an intermediate layer above the seed layer,   wherein the first oxide recording layer is formed above the intermediate layer.   
     
     
         13 . A perpendicular magnetic recording medium, comprising:
 at least two oxide recording layers positioned below a non-oxide recording layer,   wherein the at least two oxide recording layers each comprise an oxide, characterized in that the at least two oxide recording layers are adapted for controlling a grain boundary width in the recording layer.   
     
     
         14 . The perpendicular magnetic recording medium as recited in  claim 13 , wherein the at least two oxide recording layers comprise:
 a first recording layer;   a second recording layer;   a third recording layer; and   a fourth recording layer,   wherein an oxide concentration of the first recording layer is greater than an oxide concentration of the second recording layer,   wherein an oxide concentration of the third recording layer is greater than an oxide concentration of the fourth recording layer, and   wherein the oxide concentration of the third recording layer is greater than the oxide concentration of the second recording layer.   
     
     
         15 . The perpendicular magnetic recording medium as recited in  claim 14 , wherein a thickness of the first recording layer is between about 0.5 nm and about 3.0 nm, and wherein a thickness of the third recording layer is between about 1.0 nm and about 4.0 nm. 
     
     
         16 . The perpendicular magnetic recording medium as recited in  claim 14 ,
 wherein a magnetic anisotropy energy of the fourth recording layer is smaller than a magnetic anisotropy energy of the second recording layer, and   wherein a saturation magnetization of the third recording layer is lower than a saturation magnetization of the fourth recording layer.   
     
     
         17 . A magnetic data storage system, comprising:
 at least one magnetic head;   a perpendicular magnetic recording medium as recited in  claim 13 ;   a drive mechanism for passing the magnetic recording medium over the at least one magnetic head; and   a controller electrically coupled to the at least one magnetic head for controlling operation of the at least one magnetic head.