High sensitivity tunneling GMR sensors with synthetic antiferromagnet free layer

1. A magnetic sensor comprising a tunneling magnetoresistive stack, wherein the stack comprises:

a free layer comprising a synthetic antiferromagnet (SAF);

a single pinned layer; and

a bias layer.

2. The sensor of claim 1 , wherein the SAF comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer between the first and second ferromagnetic layers, wherein the first and second ferromagnetic layers have anti-parallel magnetic moments.

3. The sensor of claim 2 , wherein the first and second ferromagnetic layers comprise a ferromagnetic material selected from the group consisting of CoFe and NiFe, and the spacer layer comprises a material selected from the group consisting of Ru, Rh, Cr and Cu.

4. The sensor of claim 2 , wherein the first and second ferromagnetic layers comprise NiFe, and the spacer layer comprises a material selected from the group consisting of Rh, Cr and Cu.

5. The sensor of claim 2 , wherein the first and second ferromagnetic layers comprise NiFe, and the spacer layer comprises a material selected from the group consisting of Ru, Rh, Cr and Cu.

6. The sensor of claim 1 , wherein the magnetoresistive stack further comprises a barrier layer on the free layer and a pinned layer on the barrier layer, and wherein the pinned layer comprises a synthetic antiferromagnet (SAF).

7. The sensor of claim 6 , wherein the bias layer is disposed on the free layer opposite the barrier layer, wherein the bias layer comprises an antiferromagnetic material.

8. The sensor of claim 7 , wherein the antiferromagnetic material is selected from the group consisting of IrMn, PtMn, NiMn, RhMn, and RuRhMn.

9. The sensor of claim 7 , further comprising a second spacer layer and a ferromagnetic layer between the bias layer and the free layer.

10. The sensor of claim 9 , wherein the spacer layer is made from a material selected from the group consisting of Cu and Ru.

11. The sensor of claim 1 , wherein the SAF layer comprises a first ferromagnetic layer, a second ferromagnetic layer, and a spacer layer between the first and second ferromagnetic layers, wherein the first and second ferromagnetic layers are CoFe and have anti-parallel magnetic moments.

12. A magnetic read/write head comprising a tunneling magnetoresistive stack capable of operating in a mode wherein a sense current is applied to the stack in a direction normal to a plane of the stack, wherein the head comprises the following layers, in order:

(a) a bias layer comprising an antiferromagnetic material;

(b) a free layer comprising a synthetic antiferromagnet (SAF), wherein the SAF comprises a first ferromagnetic layer of CoFe, a second ferromagnetic layer of CoFe, and a spacer layer between the first and second ferromagnetic layers, wherein the first and second ferromagnetic layers have anti-parallel magnetic moments;

(c) a barrier layer;

(d) a pinned layer comprising a ferromagnetic layer; and

(e) a pinning layer comprising an antiferromagnetic material.

13. The read/write head of claim 12 , wherein the pinned layer is a synthetic antiferromagnet (SAF).

14. The read/write head of claim 12 , wherein the first ferromagnetic layer has a thickness T1, the second ferromagnetic layer has a thickness T2, and T1 is not equal to T2.

15. The read/write head of claim 12 , further comprising a second spacer layer and a ferromagnetic layer between the bias layer and the free layer.

16. The read/write head of claim 12 , wherein the spacer layer comprises a material selected from the group consisting of Ru, Rh, Cr and Cu.

17. The read/write head of claim 16 , wherein the spacer layer is Ru.

18. A hard disc drive comprising a magnetic read/Write head of claim 12 .

19. A computer comprising the read/write head of claim 12 .

20. A magnetic storage device comprising the read/write head of claim 12 .