Dual double-pinned spin valve element having magnet bias with increased linear range
In one aspect, a dual double-pinned spin valve element includes a first spin valve that includes a first pinned layer and a second pinned layer and a second spin valve disposed on the first spin valve and comprising a third pinned layer and a fourth pinned layer. The first, second, third and fourth pinned layers each have a magnetization in a first direction.
1. A dual double-pinned spin valve element, comprising:
a first spin valve comprising:
a first bias layer comprising a first pinned layer; and
a first reference layer comprising a second pinned layer; and
a second spin valve disposed on the first spin valve and comprising:
a second bias layer comprising a third pinned layer; and
a second reference layer comprising a fourth pinned layer,
wherein the first, second, third and fourth pinned layers each have a magnetization in a first direction.
2. The dual double-pinned spin valve element of claim 1 , wherein the first direction is perpendicular to a magnet bias direction.
3. The dual double-pinned spin valve element of claim 1 , wherein the first spin valve and the second spin valve share a pinning layer.
4. The dual double-pinned spin valve element of claim 1 , wherein the first bias layer further comprises a first pinning layer, and
wherein the first reference layer further comprises a second pinning layer.
5. The dual double-pinned spin valve element of claim 4 , wherein the first spin valve further comprises a first free layer having a magnetization in the first direction.
6. The dual double-pinned spin valve element of claim 5 , wherein the first bias layer further comprises a first spacer layer,
wherein a thickness of the first spacer layer enables ferromagnetic coupling between the first bias layer and the first free layer.
7. The dual double-pinned spin valve element of claim 4 , wherein the second bias layer further comprises a third pinning layer, and
wherein the second reference layer further comprises a fourth pinning layer.
8. The dual double-pinned spin valve element of claim 7 , wherein the second spin valve further comprises a second free layer having a magnetization antiparallel to the first direction.
9. The dual double-pinned spin valve element of claim 8 , wherein the second bias layer further comprises a second spacer layer,
wherein a thickness of the second spacer layer enables antiferromagnetic coupling between the second bias layer and the second free layer.
10. The dual double-pinned spin valve element of claim 1 , wherein the first or second spin valve is one of a tunneling magnetoresistance element or a giant magnetoresistance (GMR) element.
11. A method comprising:
depositing a stack comprising a dual double-pinned spin valve element, wherein the dual double-pinned spin valve element comprises:
a first spin valve comprising:
a first bias layer comprising a first pinned layer; and
a first reference layer comprising a second pinned layer; and
a second spin valve disposed on the first spin valve and comprising:
a second bias layer comprising a third pinned layer; and
a second reference layer comprising a fourth pinned layer;
performing an anneal on the stack,
wherein the anneal enables that each of the first, second, third and fourth pinned layers to have a magnetic direction that is parallel to each other in a first direction.
12. The method of claim 11 , wherein performing the anneal comprises performing the anneal at a temperature of about 290° C. for about an hour with a magnetic field having about 10,000 Oersted.
13. The method of claim 11 , wherein the first bias layer further comprises a first pinning layer,
wherein the first reference layer further comprises a second pinning layer,
wherein the second bias layer further comprises a third pinning layer, and
wherein the second reference layer further comprises a fourth pinning layer.
14. The method of claim 13 , wherein the first spin valve further comprises a first free layer having a magnetization in the first direction,
wherein the first bias layer further comprises a first spacer layer,
wherein a thickness of the first spacer layer enables ferromagnetic coupling between the first bias layer and the first free layer,
wherein the second spin valve further comprises a second free layer having a magnetization antiparallel to the first direction,
wherein the second bias layer further comprises a second spacer layer, and
wherein a thickness of the second spacer layer enables antiferromagnetic coupling between the second bias layer and the second free layer.
15. The method of claim 11 , wherein no other annealing is performed on the stack than the anneal.
16. A dual double-pinned spin valve element, comprising:
a first spin valve comprising:
a first bias layer comprising:
a first pinned layer; and
a first pinning layer;
a first reference layer comprising:
a second pinned layer; and
a second pinning layer; and
a second spin valve disposed on the first spin valve and comprising:
a second bias layer comprising:
a third pinned layer; and
a third pinning layer; and
a second reference layer comprising:
a fourth pinned layer; and
the second pinning layer,
wherein the first, second, third and fourth pinned layers each have a magnetization in a first direction, and
wherein the first or second spin valve is one of a tunneling magnetoresistance element or a giant magnetoresistance (GMR) element.
17. The dual double-pinned spin valve element of claim 16 , wherein the first spin valve further comprises a first free layer having a magnetization in the first direction,
wherein the first bias layer further comprises a first spacer layer,
wherein a thickness of the first spacer layer enables ferromagnetic coupling between the first bias layer and the first free layer,
wherein the second spin valve further comprises a second free layer having a magnetization antiparallel to the first direction,
wherein the second bias layer further comprises a second spacer layer, and
wherein a thickness of the second spacer layer enables antiferromagnetic coupling between the second bias layer and the second free layer.
18. The dual double-pinned spin valve element of claim 17 , wherein the first direction is perpendicular to a magnet bias direction.
19. A magnetic sensor, comprising:
a first dual double-pinned spin valve element comprising a first, second, third and fourth pinned layers each have a magnetization in a first direction; and
a second dual double-pinned spin valve element comprising a fifth, sixth, seventh and eighth pinned layers each have a magnetization in the first direction;
wherein the first dual double-pinned spin valve element and the second dual double-pinned spin valve element are connected in series or in parallel to each other,
wherein the first dual double-pinned spin valve element is biased by a first magnet in a second direction,
wherein the second dual double-pinned spin valve element is biased by a second magnet in a third direction, the third direction being in the opposite direction to the second direction.
20. The magnetic sensor of claim 19 , wherein the first direction is perpendicular to the second direction and the third direction.