Free layer for CPP GMR enhancement

Abstract

By using a composite free layer of Fe25% Co/NiFe, an improved CPP GMR device has been created. The resulting structure yields a higher CPP GMR ratio than prior art devices, while maintaining free layer softness and acceptable magnetostriction. A process for manufacturing the device is also described.

1 . A free layer for a CPP GMR device, comprising: 
 a bilayer of cobalt iron and nickel iron;    said cobalt iron layer containing at least 25 atomic percent iron; and    said free layer having a magnetostriction constant that is between 1 and 3×10 −6 .    
   
   
       2 . The free layer described in  claim 1  wherein the cobalt iron layer contacts a non-magnetic spacer layer.  
   
   
       3 . The free layer described in  claim 1  wherein the nickel iron layer contacts a non-magnetic spacer layer.  
   
   
       4 . The free layer described in  claim 1  wherein said layer of nickel iron is between about 15 and 50 Angstroms.  
   
   
       5 . The free layer described in  claim 1  wherein said layer of cobalt iron is between about 5 and 15 Angstroms thick.  
   
   
       6 . A CPP GMR read head, comprising: 
 a pinning layer on a seed layer which is on a lower lead layer;    on said pinning layer, an AP2 layer;    a layer of AFM coupling material on said AP2 layer;    an AP1 layer on said layer of AFM coupling material;    a copper spacer layer on said AP1 layer;    a layer of nickel iron on said copper spacer layer;    a layer of cobalt iron, containing at least 25 atomic percent iron, on said layer of nickel iron, said layers of nickel iron and cobalt iron together forming a free layer having a magnetostriction constant that is between 1 and 3×10 −6 ; and    on said free layer, an upper lead layer.    
   
   
       7 . The CPP GMR head described in  claim 6  wherein said pinning layer is IrMn between 45 and 80 Angstroms.  
   
   
       8 . The CPP GMR head described in  claim 6  wherein said CPP GMR read head has a GMR ratio greater than 5.9%.  
   
   
       9 . The CPP GMR head described in  claim 6  wherein said cobalt iron layer contains between about 20 and 30 atomic percent iron.  
   
   
       10 . The CPP GMR head described in  claim 6  wherein said cobalt iron layer contains between about 40 and 60 atomic percent iron.  
   
   
       11 . The CPP GMR head described in  claim 6  wherein said cobalt iron layer contains between about 70 and 80 atomic percent iron.  
   
   
       12 . The CPP GMR head described in  claim 6  wherein said layer of nickel iron has a thickness of between about 15 and 50 Angstroms.  
   
   
       13 . The CPP GMR head described in  claim 6  wherein said layer of cobalt iron has a thickness of between about 5 and 15 Angstroms.  
   
   
       14 . The CPP GMR head described in  claim 6  wherein said free layer has a coercivity between about 5 and 10 Oe.  
   
   
       15 . A CPP GMR read head, comprising: 
 a pinning layer on a seed layer which is on a lower lead layer;    on said pinning layer, an AP2 layer;    a layer of AFM coupling material on said AP2 layer;    an AP1 layer on said layer of AFM coupling material;    a copper spacer layer on said AP1 layer;    a layer of cobalt iron, containing at least 25 atomic percent iron, on said copper spacer layer;    a layer of nickel iron on said layer of cobalt iron, said cobalt iron and nickel iron layers together forming a free layer having a magnetostriction constant that is between 1 and 3×10 −6 ; and    on said free layer, an upper lead layer.    
   
   
       16 . The CPP GMR head described in  claim 15  wherein said CPP GMR read head has a GMR ratio greater than 5.9%.  
   
   
       17 . The CPP GMR head described in  claim 15  wherein said layer of nickel iron has a thickness of between about 15 and 50 Angstroms.  
   
   
       18 . The CPP GMR head described in  claim 15  wherein said layer of cobalt iron has a thickness of between about 5 and 15 Angstroms.  
   
   
       19 . The CPP GMR head described in  claim 15  wherein said free layer has a coercivity between about 5 and 10 Oe.