Perpendicular magnetic recording medium, manufacturing process of the same, and magnetic recording/reproducing apparatus using the same

Abstract

Embodiments of the invention provide a perpendicular magnetic recording medium improved for fly ability, high in read signal quality, and capable of suppressing magnetic decay of recorded magnetization to be caused by stray fields. In one embodiment, a perpendicular recording layer is formed over a substrate with a soft magnetic underlayer therebetween, then an amorphous or nano-crystalline layer is formed between the substrate and the soft magnetic underlayer. The soft magnetic underlayer includes first and second amorphous soft magnetic layers, as well as a nonmagnetic layer formed between those first and second amorphous soft magnetic layers. The first and second amorphous soft magnetic layers are given uniaxial anisotropy in the radial direction of the substrate respectively and coupled with each other antiferromagnetically.

1 .- 25 . (canceled) 
     
     
         26 . A perpendicular magnetic recording medium including:
 a perpendicular recording layer formed over a substrate with a soft magnetic underlayer therebetween,   wherein said perpendicular magnetic recording medium further includes an amorphous layer or nano-crystalline layer formed directly above said substrate and directly below said soft magnetic underlayer;   wherein said soft magnetic underlayer includes first and second amorphous soft magnetic layers, and a nonmagnetic layer formed between said first and second amorphous soft magnetic layers; and   wherein said first and second amorphous soft magnetic layers are coupled with each other antiferromagnetically;   wherein said amorphous layer or nano-crystalline layer includes an alloy that contains at least two or more metals selected from a group consisting of Al, Ti, Ta, Cr, Zr, Co, Hf, Si, and B.   
     
     
         27 . The perpendicular magnetic recording medium according to  claim 26 , wherein said amorphous layer or nano-crystalline layer comprises CrTa or CrTi. 
     
     
         28 . The perpendicular magnetic recording medium according to  claim 26 , wherein said first and second amorphous soft magnetic layers are given uniaxial magnetic anisotropy in a radial direction of said substrate respectively. 
     
     
         29 . The perpendicular magnetic recording medium according to  claim 26 , wherein said medium further includes a first ferromagnetic layer between said first amorphous soft magnetic layer and said nonmagnetic layer and a second ferromagnetic layer between said second amorphous soft magnetic layer and said nonmagnetic layer. 
     
     
         30 . The perpendicular magnetic recording medium according to  claim 26 , wherein a magnetization curve of said soft magnetic underlayer measured by applying a magnetic field to said substrate in the radial direction has a step-like shape containing a magnetization level stable within a magnetic field that includes a zero field while an absolute value of a switching field of which level is to be changed from negative field side saturation magnetization to said stable magnetization is almost the same as an absolute value of a switching field of which level is to be changed from positive field side saturation magnetization to said stable magnetization level. 
     
     
         31 . A magnetic recording/reproducing apparatus, comprising:
 a perpendicular magnetic recording medium according to  claim 26 ;   a motor element for rotating the perpendicular magnetic recording medium; and   a magnetic head for at least one of reading from and writing to the perpendicular magnetic recording medium.   
     
     
         32 . The apparatus according to  claim 31 , wherein a write element of said magnetic head is formed as a single-pole type head and a read element of said magnetic head is formed as a sensitive device that makes use of magnetoresistance or tunneling magnetoresistance. 
     
     
         33 . A perpendicular magnetic recording medium including:
 a perpendicular recording layer formed over a substrate with a soft magnetic underlayer therebetween,   wherein said perpendicular magnetic recording medium further includes an amorphous layer formed directly on said substrate, said soft magnetic underlayer being formed directly on said amorphous layer with no other intervening layers therebetween;   wherein said soft magnetic underlayer includes first and second amorphous soft magnetic layers, and a nonmagnetic layer formed between said first and second amorphous soft magnetic layers; and   wherein said first and second amorphous soft magnetic layers are coupled with each other antiferromagnetically;   wherein said amorphous layer includes an alloy that contains at least two or more metals selected from a group consisting of Al, Ti, Ta, Cr, Zr, Co, Hf, Si, and B.   
     
     
         34 . The perpendicular magnetic recording medium according to  claim 33 , wherein said amorphous layer comprises CrTa or CrTi. 
     
     
         35 . The perpendicular magnetic recording medium according to  claim 33 , wherein said first and second amorphous soft magnetic layers are given uniaxial magnetic anisotropy in a radial direction of said substrate respectively. 
     
     
         36 . The perpendicular magnetic recording medium according to  claim 33 , wherein said medium further includes a first ferromagnetic layer between said first amorphous soft magnetic layer and said nonmagnetic layer and a second ferromagnetic layer between said second amorphous soft magnetic layer and said nonmagnetic layer. 
     
     
         37 . The perpendicular magnetic recording medium according to  claim 33 , wherein a magnetization curve of said soft magnetic underlayer measured by applying a magnetic field to said substrate in the radial direction has a step-like shape containing a magnetization level stable within a magnetic field that includes a zero field while an absolute value of a switching field of which level is to be changed from negative field side saturation magnetization to said stable magnetization is almost the same as an absolute value of a switching field of which level is to be changed from positive field side saturation magnetization to said stable magnetization level. 
     
     
         38 . A magnetic recording/reproducing apparatus, comprising:
 a perpendicular magnetic recording medium according to  claim 33 ;   a motor element for rotating the perpendicular magnetic recording medium; and   a magnetic head for at least one of reading from and writing to the perpendicular magnetic recording medium.   
     
     
         39 . The apparatus according to  claim 38 , wherein a write element of said magnetic head is formed as a single-pole type head and a read element of said magnetic head is formed as a sensitive device that makes use of magnetoresistance or tunneling magnetoresistance. 
     
     
         40 . The perpendicular magnetic recording medium according to  claim 33 , wherein said amorphous layer is a CrTi layer. 
     
     
         41 . The perpendicular Magnetic recording medium according to  claim 33 , wherein said amorphous layer is a CrTa layer. 
     
     
         42 . The perpendicular magnetic recording medium according to  claim 33 , wherein said amorphous layer is a AlTi layer. 
     
     
         43 . The perpendicular magnetic recording medium according to  claim 33 , wherein said soft magnetic underlayer comprises Fe, Co, Cr and B. 
     
     
         44 . The perpendicular magnetic recording medium according to  claim 43 , wherein said amorphous layer or nano-crystalline layer comprises at least one of Al and Cr and at least one of Ta and Ti. 
     
     
         45 . The perpendicular magnetic recording medium according to  claim 33 , wherein said soft magnetic underlayer comprises Fe, Ta and Zr. 
     
     
         46 . The perpendicular magnetic recording medium according to  claim 45 , wherein said amorphous layer or nano-crystalline layer comprises at least one of Al and Cr and at least one of Ta and Ti. 
     
     
         47 . The perpendicular magnetic recording medium according to  claim 33 , wherein said soft magnetic underlayer comprises Co, Fe, Ta and Zr. 
     
     
         48 . The perpendicular magnetic recording medium according to  claim 47 , wherein said amorphous layer or nano-crystalline layer comprises at least one of Al and Cr and at least one of Ta and Ti. 
     
     
         49 . The perpendicular magnetic recording medium according to  claim 26 , wherein said amorphous layer or nano-crystalline layer is a CrTi layer. 
     
     
         50 . The perpendicular magnetic recording medium according to  claim 26 , wherein said amorphous layer or nano-crystalline layer is a CrTa layer. 
     
     
         51 . The perpendicular magnetic recording medium according to  claim 26 , wherein said amorphous layer or nano-crystalline layer is a AlTi layer. 
     
     
         52 . The perpendicular magnetic recording medium according to  claim 26 , wherein said amorphous layer or nano-crystalline layer comprises at least one of Al and Cr and at least one of Ta and Ti. 
     
     
         53 . The perpendicular magnetic recording medium according to  claim 52 , wherein said soft magnetic underlayer comprises Fe, Co, Cr and B. 
     
     
         54 . The perpendicular magnetic recording medium according to  claim 26 , wherein said soft magnetic underlayer comprises Fe, Ta and Zr. 
     
     
         55 . The perpendicular magnetic recording medium according to  claim 54 , wherein said soft magnetic underlayer comprises Fe, Co, Cr and B. 
     
     
         56 . The perpendicular magnetic recording medium according to  claim 26 , wherein said soft magnetic underlayer comprises Co, Fe, Ta and Zr. 
     
     
         57 . The perpendicular magnetic recording medium according to  claim 56 , wherein said soft magnetic underlayer comprises Fe, Co, Cr and B.