Underlayer for reference layer of polycrystalline cpp gmr sensor stack

Abstract

Embodiments disclosed herein generally relate to a magnetic head having an amorphous ferromagnetic reference layer. The ferromagnetic reference layer may have amorphous structure as a result of an amorphous ferromagnetic underlayer that the ferromagnetic reference layer is deposited thereon. The amorphous ferromagnetic reference layer enhances magnetoresistance, leading to an improved magnetic head.

What is claimed is: 
     
         1 . A magnetic head, comprising:
 a sensor stack, wherein the sensor stack includes:
 an antiferromagnetic layer; 
 a ferromagnetic pinned layer disposed on the antiferromagnetic layer; 
 a first nonmagnetic layer disposed on the ferromagnetic pinned layer; 
 a first crystalline ferromagnetic underlayer disposed on the first nonmagnetic layer; 
 an amorphous ferromagnetic reference layer disposed over the first crystalline ferromagnetic underlayer; 
 a second nonmagnetic layer disposed on the amorphous ferromagnetic reference layer; 
 a second crystalline ferromagnetic underlayer disposed on the second nonmagnetic layer; and 
 a ferromagnetic free layer disposed over the second crystalline ferromagnetic underlayer. 
   
     
     
         2 . The magnetic head of  claim 1 , further comprising a first amorphous ferromagnetic underlayer disposed between the first crystalline ferromagnetic underlayer and the amorphous ferromagnetic reference layer. 
     
     
         3 . The magnetic head of  claim 2 , wherein the first amorphous ferromagnetic underlayer comprises CoFeBTa, CoTiB or CoFeGe. 
     
     
         4 . The magnetic head of  claim 2 , further comprising a second amorphous ferromagnetic underlayer disposed between the second crystalline ferromagnetic underlayer and the ferromagnetic free layer. 
     
     
         5 . The magnetic head of  claim 4 , wherein the second amorphous ferromagnetic underlayer comprises CoFeBTa, CoTiB or CoFeGe. 
     
     
         6 . The magnetic head of  claim 1 , wherein the ferromagnetic free layer is amorphous. 
     
     
         7 . The magnetic head of  claim 1 , wherein the amorphous ferromagnetic reference layer is deposited on the first crystalline ferromagnetic underlayer at a temperature between about 50 K to about 100 K.