Spin valve with bias alignment

Abstract

A magnetoresistance element (e.g. a spin valve) for detecting a changing magnetic field includes a pinning layer, pinned layer adjacent to the pinning layer, a spacer layer adjacent to the pinned layer, and a free layer adjacent to the spacer layer and arranged so that the spacer layer is between the pinned layer and the free layer. The pinned layer has a bias with a bias direction configured to reduce an effect of a static field on the detection of the changing magnetic field.

What is claimed is: 
     
         1 . A magnetoresistance element for detecting a changing magnetic field in an environment having a static magnetic field having a magnitude and a direction, the magnetoresistance element comprising:
 a first spin valve comprising:
 a pinning layer; 
 a pinned layer adjacent to the pinning layer; 
 a spacer layer adjacent to the pinned layer; and 
 a free layer adjacent to the spacer layer and arranged so that the spacer layer is between the pinned layer and the free layer, 
   wherein the first spin valve has a bias with a magnitude and a direction, wherein the direction of the bias is opposite the direction of the static magnetic field, and   wherein the static magnetic field is generated external to the magnetoresistance element.   
     
     
         2 . The magnetoresistance element of  claim 1 , further comprising a biasing structure comprising a spacer layer, a pinned layer, and a pinning layer configured to apply a magnetic bias to the free layer. 
     
     
         3 . The magnetoresistance element of  claim 1 , wherein the pinned layer comprises:
 a first ferromagnetic layer;   a second ferromagnetic layer; and   a nonmagnetic layer between the first and second ferromagnetic layers.   
     
     
         4 . The magnetoresistance element of  claim 1 , wherein the free layer comprises a ferromagnetic layer. 
     
     
         5 . The magnetoresistance element of  claim 1 , wherein the magnetoresistance element is a spin valve. 
     
     
         6 . The magnetoresistance element of  claim 1 , wherein the magnitude of the bias is equal to a magnitude of the static magnetic field. 
     
     
         7 . The magnetoresistance element of  claim 1  wherein an axis of maximum sensitivity of the magnetoresistance element is positioned to detect the changing magnetic field. 
     
     
         8 . A magnetoresistance element for detecting a changing magnetic field in an environment having a static magnetic field having a magnitude and a direction, the magnetoresistance element comprising:
 a first spin valve comprising:
 a first pinning layer; 
 a first pinned layer adjacent to the first pinning layer; 
 a first spacer layer adjacent to the first pinned layer; 
 a free layer adjacent to the first spacer layer and arranged so that the first spacer layer is between the first pinned layer and the free layer; 
 a second pinning layer; 
 a second pinned layer adjacent to the second pinning layer; and 
 a second spacer layer adjacent to the second pinned layer and the free layer, 
   wherein the first spin value is a first double-pinned spin valve,   wherein the first spin valve has a bias with a magnitude and a direction, and   wherein the static magnetic field is generated external to the magnetoresistance element.   
     
     
         9 . The magnetoresistance element of  claim 8 , wherein the static magnetic field is defined by a first magnetic vector and the bias of the first spin valve is defined by a second magnetic vector, wherein the sum of the first and second magnetic vectors results in a system bias vector that is substantially perpendicular to a direction of maximum sensitivity of the magnetoresistance element. 
     
     
         10 . The magnetoresistance element of  claim 8 , further comprising a second double-pinned spin valve, wherein the second pinning layer is a shared layer between the first double-pinned spin valve and the second double-pinned spin valve. 
     
     
         11 . The magnetoresistance element of  claim 8 , wherein the free layer comprises a ferromagnetic layer. 
     
     
         12 . A magnetic field sensor comprising:
 at least one magnetoresistance element for detecting a changing magnetic field in an environment having a static magnetic field having a magnitude and a direction, the magnetoresistance element comprising a first spin valve comprising:
 a pinning layer; 
 a pinned layer; 
 a spacer layer adjacent to the pinned layer; and 
 a free layer adjacent to the spacer layer and arranged so that the spacer layer is between the pinned layer and the free layer, wherein the first spin valve has a bias with a direction and a magnitude, 
   wherein the direction of the bias is opposite the direction of the static magnetic field, and   wherein the static magnetic field is generated external to the magnetoresistance element.   
     
     
         13 . The magnetic field sensor of  claim 12 , wherein a pinning layer is a first pinning layer, a pinned layer is a first pinned layer and a spacer layer is a first spacer layer, and
 wherein the first spin valve further comprises:
 a second pinning layer; 
 a second pinned layer adjacent to the second pinning layer; and 
 a second spacer layer adjacent to the second pinned layer and the free layer. 
   
     
     
         14 . The magnetic field sensor of  claim 12 , wherein the at least one magnetoresistance element is a double-pinned spin valve. 
     
     
         15 . The magnetic field sensor of  claim 12 , wherein an axis of maximum sensitivity of the at least one magnetoresistance element is positioned to detect the changing magnetic field. 
     
     
         16 . The magnetic field sensor of  claim 12 , wherein the at least one magnetoresistance element comprises a plurality of magnetoresistance elements arranged in a bridge configuration. 
     
     
         17 . The magnetic field sensor of  claim 12 , wherein the at least one magnetoresistance element is chosen from the list consisting of: a simple spin valve, a double-pinned spin valve, and a double spin valve. 
     
     
         18 . The magnetic field sensor of  claim 12 , wherein the magnitude of the bias is equal to a magnitude of the static magnetic field. 
     
     
         19 . The magnetoresistance element of  claim 12 , wherein the free layer comprises a ferromagnetic layer.