Supermalloy and MU Metal Side and Top Shields for Magnetic Read Heads

Abstract

The use of supermalloy-like materials such as NiFeMe where Me is one or more of Mo, Cr, and Cu for the side and top shields of a magnetic bit sensor is shown to provide better shielding protection from stray fields because of their extremely high permeability. Moreover, the side shield may comprise a stack in which a Ni, Fe, Co, FeNi, CoFe, or FeCo is sandwiched between two NiFeMe layers to enhance the bias field on an adjacent free layer. Including NiFeMe in a side shield results in an increase in readback amplitude under the same asymmetric sigma. For these sensors, the signal to noise ratio was higher and the bit error rate was lower than with conventional materials in the side shield.

We claim: 
     
         1 . A method of forming a magnetic bit sensor, comprising:
 (a) providing a lower magnetic shield and forming on a portion thereof a magnetic bit sensor that includes sidewalls and a free layer;   (b) then depositing, on all uncovered portions of the lower magnetic shield and on the sidewalls, one or more layers of NiFeMe where Me is one or more of Mo, Cr, and Cu thereby forming a side shield that has a coercivity less than or equal to 1.0 Oe, the side shield provides a biasing field to the free layer and has a top surface on the one or more NiFeMe layers; and   (c) depositing a top shield that fully contacts and covers the magnetic bit sensor and contacts a top surface of the side shield.   
     
     
         2 . The method of  claim 1  wherein a first layer that is one of the NiFeMe layers is deposited on the lower magnetic shield, and forming the side shield is further comprised of depositing a magnetic layer on the first layer, the magnetic layer is Ni, Co, Fe, FeNi, CoFe, or FeCo to increase an effective moment of the magnetic bit sensor, and then depositing a second layer that is one of the NiFeMe layers on the magnetic layer, the second layer has a top surface that is the top surface of the side shield. 
     
     
         3 . The method of  claim 1  wherein the top shield is comprised of a NiFeMe layer. 
     
     
         4 . The method of  claim 1  wherein both of the top shield and the lower magnetic shield are comprised of a NiFeMe layer. 
     
     
         5 . A method of forming a magnetic bit sensor, comprising:
 (a) providing a lower magnetic shield and forming on a first portion thereof a magnetic bit sensor that includes sidewalls and a free layer thereby leaving a second portion of the lower magnetic shield uncovered;   (b) forming a side shield on the magnetic bit sensor sidewalls and on the second portion of the lower magnetic shield so as to provide a bias field to the free layer, the side shield comprises:
 (1) a lower NiFeMe layer where Me is one or more of Mo, Cr, and Cu; 
 (2) a middle magnetic layer with a magnetic moment greater than the lower NiFeMe layer; and 
 (3) an upper layer that is a second NiFeMe layer or a non-magnetic layer, the upper layer has a top surface that is a top surface of the side shield; and 
   (c) depositing a top shield that fully contacts and covers the magnetic bit sensor and contacts the top surface of the side shield.   
     
     
         6 . The method of  claim 5  wherein the magnetic layer comprises Ni, Co, Fe, FeNi, CoFe, or FeCo to increase an effective moment of the side shield and thereby increase a strength of the bias field. 
     
     
         7 . The method of  claim 5  wherein the top shield is comprised of a lower NiFeMe layer and an upper magnetic layer. 
     
     
         8 . The method of  claim 5  wherein both of the top shield and the lower magnetic shield are comprised of NiFeMe. 
     
     
         9 . A magnetic bit sensor, comprising:
 (a) a lower magnetic shield;   (b) a magnetic bit sensor that includes sidewalls and a free layer, the magnetic bit sensor is formed on a first portion of the lower magnetic shield;   (c) a side shield having a top surface and comprised of one or more layers of NiFeMe with a coercivity less than or equal to 1.0 Oe where Me is one or more of Mo, Cr, and Cu, the side shield is formed on a second portion of the lower magnetic shield that is not covered by the magnetic bit sensor and on the sidewalls of the magnetic bit sensor; and   (d) a top shield that fully contacts and covers the magnetic bit sensor and contacts the top surface of the side shield.   
     
     
         10 . The magnetic bit sensor of  claim 9  wherein the side shield further comprises a magnetic layer that is one of Ni, Co, Fe, FeNi, CoFe, and FeCo, the magnetic layer increases an effective moment of the side shield thereby increasing a strength of the bias field. 
     
     
         11 . The magnetic bit sensor of  claim 9  wherein the top shield comprises NiFeMe, and has a coercivity that is less than or equal to 1.0 Oe. 
     
     
         12 . The magnetic bit sensor of  claim 9  wherein both of the top shield and the lower magnetic shield are comprised of NiFeMe, and have a coercivity that is less than or equal to 1.0 Oe.