Patent ID: 8237437

Claim:
A ferromagnetic thin-film based magnetic field sensor comprising two or more reference layer magnetization directions, comprising: a substrate having a surface forming a plane; a first insulating layer over the substrate; a first sense axis comprising a first Wheatstone bridge comprising first, second, third, and fourth sensor layer stacks, respectively, each over the first insulating layer, each of the first, second, third, and fourth sensor layer stacks having a tunnel barrier layer between a sense layer and a reference layer structure, wherein each of the reference layer structures within the first, second, third, and fourth sensor layer stacks have a first reference magnetization direction; and a second sense axis comprising a second Wheatstone bridge and comprising fifth, sixth, seventh, and eighth sensor layer stacks, respectively, over the first insulating layer, each of the fifth, sixth, seventh, and eighth sensor layer stacks comprising a tunnel barrier layer between a sense layer and a reference layer structure wherein each of the reference layer structures within the fifth, sixth, seventh, and eight sensor layer stacks have a second identical reference magnetization direction; wherein the first, second, third, fourth, fifth, sixth, seventh, and eighth reference layer structures each comprise an imbalanced synthetic antiferromagnet formed with first and second ferromagnetic layers separated by a spacer layer, the first and second ferromagnetic layers having different magnetic moments, the first, second, third, and fourth reference layer structures having a first width and a first shape oriented parallel to the plane to set a first reference direction along the short axis of the first, second, third, and fourth reference layer structures, and the fifth, sixth, seventh, and eighth reference layer structures having a second width and a second shape oriented parallel to the plane to set second reference direction along the short axis of the fifth, sixth, seventh, and eighth reference layer structure that is different from the first reference direction.