TMR sensor with magnetic tunnel junctions with a free layer having an intrinsic anisotropy
Embodiments of the present disclosure generally relate to a large field range TMR sensor of magnetic tunnel junctions (MTJs) with a free layer having an intrinsic anisotropy. In one embodiment, a tunnel magnetoresistive (TMR) based magnetic sensor in a Wheatstone configuration includes at least one MTJ. The MTJ includes a free layer having an intrinsic anisotropy produced by deposition at a high oblique angle from normal. Magnetic domain formations within the free layer can be further controlled by a pinned layer canted at an angle to the intrinsic anisotropy of the free layer, by a hard bias element, by shape anisotropy, or combinations thereof.
1. A tunnel magnetoresistive (TMR) based magnetic sensor in a Wheatstone configuration, comprising:
at least one magnetic tunnel junction (MTJ), the at least one MTJ comprising:
a free layer deposited at a high oblique angle from normal, the free layer having an intrinsic anisotropy, wherein a magnetization direction of the intrinsic anisotropy is substantially orthogonal to a plane of incidence of deposition at the high oblique angle.
2. The TMR based magnetic sensor of claim 1 , wherein the high oblique angle is from 55° to 85°.
3. The TMR based magnetic sensor of claim 1 , wherein the free layer comprises a first sub-layer and a second sub-layer.
4. The TMR based magnetic sensor of claim 3 , wherein the first sub-layer is formed by static deposition over a substrate in a first position and wherein the second sub-layer is formed by static deposition over the substrate in a second position rotated from the first position.
5. The TMR based magnetic sensor of claim 1 , wherein the intrinsic anisotropy is from about 80 Oe to about 1600 Oe.
6. The TMR based magnetic sensor of claim 1 , wherein at least one MTJ further comprises a pinned layer with a magnetization direction at an angle from about 40° to 50° from the intrinsic anisotropy of the free layer.
7. The TMR based magnetic sensor of claim 1 , wherein the at least one MTJ further comprises:
a pinned layer;
an antiparallel coupling layer; and
an antiferromagnetic pinning layer.
8. A tunnel magnetoresistive (TMR) based magnetic sensor in a Wheatstone configuration, comprising:
at least one magnetic tunnel junction (MTJ), the at least one MTJ comprising:
a free layer deposited at a high angle from normal, the free layer having an intrinsic anisotropy; and
a pinned layer having a magnetization direction orthogonal to the intrinsic anisotropy of the free layer;
wherein the at least one MTJ has a hard bias element positioned proximate the free layer.
9. The TMR based magnetic sensor of claim 8 , wherein a magnetic moment of the hard bias element is rotated in reference to the intrinsic anisotropy of the free layer.
10. The TMR based magnetic sensor of claim 9 , wherein the hard bias element is formed around the free layer.
11. The TMR based magnetic sensor of claim 9 , wherein the hard bias element comprises a first hard bias sub-element and second hard bias sub-element.
12. The TMR based magnetic sensor of claim 8 , wherein the free layer further has shape anisotropy, wherein the magnetization direction of the pinned layer is orthogonal to the intrinsic anisotropy and the shape anisotropy of the free layer.
13. The TMR based magnetic sensor of claim 12 , wherein the free layer is shaped as an elongated polygon having a width and a height with a width-to-height aspect ratio of about 4:1 or more.
14. A tunnel magnetoresistive (TMR) based magnetic sensor in a Wheatstone configuration, comprising:
at least one of magnetic tunnel junction (MTJ), the at least one MTJ comprising:
a pinned layer;
a barrier layer over the pinned layer; and
a free layer over the barrier layer; the free layer having an intrinsic anisotropy from about 200 Oe to about 1600 Oe, wherein the free layer has micro ridges in a direction of the intrinsic anisotropy.
15. The TMR based magnetic sensor of claim 14 , wherein a magnetization direction of the pinned layer is orthogonal to the intrinsic anisotropy of the free layer.
16. The TMR based magnetic sensor of claim 14 , wherein a magnetic moment of a hard bias element is rotated in reference to the intrinsic anisotropy of the free layer.
17. The TMR based magnetic sensor of claim 14 , wherein the free layer further has shape anisotropy, wherein a magnetization direction of the pinned layer is orthogonal to the intrinsic anisotropy and the shape anisotropy of the free layer.
18. The TMR based magnetic sensor of claim 17 , wherein the free layer is shaped as an elongated polygon having a width and a height with a width-to-height aspect ratio of about 4:1 or more.
19. The TMR based magnetic sensor of claim 14 , wherein the at least one MTJ further comprises an antiferromagnetic pinning layer disposed on the pinned layer.
20. A tunnel magnetoresistive (TMR) based magnetic sensor in a Wheatstone configuration, comprising:
at least one of magnetic tunnel junction (MTJ), the at least one MTJ comprising:
a pinned layer;
a barrier layer over the pinned layer; and
a free layer over the barrier layer; the free layer having an intrinsic anisotropy from about 200 Oe to about 1600 Oe, wherein the at least one MTJ has a hard bias element positioned proximate the free layer.