Granular perpendicular magnetic recording media with dual recording layer and method of fabricating same

Abstract

A granular perpendicular magnetic recording medium comprises a non-magnetic substrate and a granular perpendicular magnetic recording layer overlying the substrate, comprising a first granular perpendicular magnetic layer proximal the substrate and having a first saturation magnetization (M s ) 1 , and a second granular perpendicular magnetic layer distal the substrate and having a second, different saturation magnetization (M s ) 2 . Also disclosed is a method of fabricating the granular perpendicular magnetic recording medium.

1 - 29 . (canceled) 
     
     
         30 . A method comprising:
 forming on a non-magnetic substrate a perpendicular magnetic recording medium, wherein the magnetic recording medium comprises a magnetic recording layer, the magnetic recording layer comprising at least two granular perpendicular magnetic layers, wherein each of the granular perpendicular magnetic layers consists of a CoPt magnetic alloy and a non-magnetic oxide material at boundaries between adjacent magnetic grains, wherein the amount of non-magnetic oxide material in the granular magnetic recording layers is selected such that the granular perpendicular magnetic layer closest to the substrate has the lowest saturation magnetization (M s ), and wherein the (M s ) of the granular perpendicular magnetic layer closest to the substrate is between about 200 and about 600 emu/cc.   
     
     
         31 . The method of  claim 30 , wherein the magnetic oxide material in the magnetic layers is selected from at least one of TiO 2 , SiO 2 , Nb 2 O 5 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , V 2 O 5  or Y 2 O 3 . 
     
     
         32 . The method of  claim 30 , wherein a granular perpendicular magnetic layer farthest from the substrate has a saturation magnetization (M s ) at least 20% greater than the saturation magnetization (M s ) of the granular perpendicular magnetic layer closest to the substrate. 
     
     
         33 . The method of  claim 30 , further comprising forming a magnetically soft underlayer (SUL) between the substrate and the granular perpendicular magnetic layer closest to the substrate. 
     
     
         34 . The method of  claim 30 , wherein the CoPt magnetic alloy in a granular perpendicular magnetic recording layer farthest from the substrate has greater than about 60 at % Co and greater than about 12 at % Pt. 
     
     
         35 . The method of  claim 31 , wherein the non-magnetic oxide material in the granular perpendicular magnetic recording layer closest to the substrate is 6-12 mol % of TiO 2 , SiO 2 , or Al 2 O 3 , or 5-10 mol % of Ta 2 O 5 , ZrO 2 , V 2 O 5  or Y 2 O 3 . 
     
     
         36 . The method of farthest from  claim 30 , wherein the granular perpendicular magnetic recording layer closest to the substrate has a thickness of about 10 to about 200 Å, and granular perpendicular magnetic recording layer farthest from the substrate has a thickness of about 2 to about 200 Å. 
     
     
         37 . A method for making a magnetic recording medium, comprising depositing on a non-magnetic substrate the following layers, in order:
 a non-magnetic substrate;   a soft magnetic underlayer;   an interlayer comprising Ru or a Ru alloy;   a first granular perpendicular magnetic layer having a first saturation magnetization (M s ) 1 , wherein the first granular perpendicular magnetic layer consists of a CoPt magnetic alloy and a non-magnetic oxide material at boundaries between adjacent magnetic grains, and wherein the magnetic oxide material in the first granular perpendicular magnetic layer is selected from at least one of TiO 2 , SiO 2 , Nb 2 O 5 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , V 2 O 5  or Y 2 O 3 ,   a second granular perpendicular magnetic layer having a second, different saturation magnetization (M s ) 2 , wherein the second perpendicular granular magnetic layer consists of a CoPt magnetic alloy and a non-magnetic oxide material at boundaries between adjacent magnetic grains, and wherein the magnetic oxide material in the second granular perpendicular magnetic layer is selected from at least one of TiO 2 , SiO 2 , Nb 2 O 5 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , V 2 O 5  or Y 2 O 3,  and wherein (M s ) 1  is about 200 emu/cc to about 600 emu/cc, and (M s ) 2  is greater than about 600 emu/cc and at least 20% greater than (M s ) 1 ;   a protective overcoat; and   a lubricant topcoat.