Thin sul perpendicular magnetic recording media and recording systems comprising same

Abstract

A perpendicular magnetic recording system, comprises: a perpendicular magnetic recording medium including a non-magnetic substrate having a surface and a stacked plurality of thin film layers forming a layer stack overlying the substrate surface and including a magnetically soft underlayer (SUL) beneath at least one perpendicular magnetic recording layer, wherein the SUL has a saturation magnetization (M s )—thickness (t) product (M s t) less than about 4 memu/cm 2 , and a ring-type magnetic transducer head is positioned in spaced adjacency to an upper surface of the layer stack.

1 . A perpendicular magnetic recording medium, comprising:
 (a) a non-magnetic substrate having a surface; and   (b) a stacked plurality of thin film layers forming a layer stack overlying said substrate surface and including a magnetically soft underlayer (SUL) beneath at least one perpendicular magnetic recording layer, said SUL having a saturation magnetization (M s )—thickness (t) product (M s t) less than about 4 memu/cm 2 .   
     
     
         2 . The medium as in  claim 1 , wherein:
 said SUL comprises a material having a saturation magnetization (M s ) of about 500 to about 2,000 emu/cc and a thickness from about 1 to about 40 nm.   
     
     
         3 . The medium as in  claim 1 , wherein:
 said SUL and said at least one perpendicular magnetic recording layer are spaced apart at a spacing determined by an interlayer stack between said SUL and said at least one perpendicular magnetic recording layer.   
     
     
         4 . The medium as in  claim 3 , wherein:
 said SUL and said at least one perpendicular magnetic recording layer are spaced apart from about 5 to about 200 nm.   
     
     
         5 . The medium as in  claim 4 , wherein:
 said SUL and said at least one perpendicular magnetic recording layer are spaced apart from about 30 to about 100 nm.   
     
     
         6 . The medium as in  claim 3 , wherein:
 said interlayer stack includes a spacer layer and an interlayer.   
     
     
         7 . The medium as in  claim 6 , wherein:
 said spacer layer comprises an amorphous material and said interlayer comprises an hcp material with a preferred c-axis perpendicular growth orientation.   
     
     
         8 . The medium as in  claim 6 , wherein:
 said interlayer stack further includes a seed layer.   
     
     
         9 . The medium as in  claim 1 , wherein:
 said SUL has a saturation magnetization (M s )—thickness (t) product (M s t) less than about 1 memu/cm 2 .   
     
     
         10 . The medium as in  claim 1 , wherein:
 said SUL comprises a material having a magnetic permeability greater than about 10 and a thickness less than about 10 nm.   
     
     
         11 . The medium as in  claim 1 , wherein:
 said SUL comprises at least one soft magnetic material selected from the group consisting of: Ni, Co, Fe, NiFe (Permalloy), FeN, FeSiAl, FeSiAlN, CoZr, CoZrCr, CoZrNb, CoFeZrNb, CoFe, FeCoB, and FeCoC.   
     
     
         12 . The medium as in  claim 1 , wherein:
 said at least one perpendicular magnetic recording layer comprises an hcp Co-based alloy with a preferred c-axis perpendicular growth orientation.   
     
     
         13 . The medium as in  claim 12 , wherein:
 said at least one perpendicular magnetic recording layer comprises at least partially isolated magnetic particles or grains with c-axis growth orientation.   
     
     
         14 . The medium as in  claim 12 , wherein:
 said at least one perpendicular magnetic recording layer comprises a granular layer with uniform grain size, composition, and crystallographic orientation.   
     
     
         15 . The medium as in  claim 1 , wherein:
 said layer stack comprises a protective overcoat layer above said at least one perpendicular magnetic recording layer and a lubricant topcoat layer over said protective overcoat layer.   
     
     
         16 . The medium as in  claim 15 , wherein:
 said protective overcoat layer comprises a carbon-based material and said lubricant topcoat layer comprises a fluoropolymer material.   
     
     
         17 . The medium as in  claim 1 , wherein:
 said non-magnetic substrate comprises a material selected from the group consisting of: Al, Al—Mg alloys, other Al-based alloys, NiP-plated Al or Al-based alloys, glass, ceramics, glass-ceramics, polymeric materials, and composites or laminates of these materials.   
     
     
         18 . A perpendicular magnetic recording system, comprising:
 (a) a perpendicular magnetic recording medium including:
 (i) a non-magnetic substrate having a surface; and 
 (ii) a stacked plurality of thin film layers forming a layer stack overlying said substrate surface and including a magnetically soft underlayer (SUL) beneath and spaced from at least one perpendicular magnetic recording layer, said SUL having a saturation magnetization (M s )—thickness (t) product (M s t) less than about 4 memu/cm 2 ; and 
   (b) a ring-type magnetic transducer head positioned in spaced adjacency to an upper surface of said layer stack to form a head gap, said transducer head comprising leading and trailing poles.   
     
     
         19 . The system as in  claim 18 , wherein:
 said SUL has a saturation magnetization (M s )—thickness (t) product (M s t) less than about 4 memu/cm 2 .   
     
     
         20 . The system as in  claim 18 , wherein:
 the orientation ratio of said medium of said system is greater than about 10.