Double pinned magnetoresistance element with temporary ferromagnetic layer to improve annealing

1. A magnetoresistance element deposited upon a substrate, comprising:

a first synthetic antiferromagnet (SAF) structure, comprising:

a first ferromagnetic layer;

a second ferromagnetic layer; and

a first spacer layer between the first and second ferromagnetic layers of the first synthetic antiferromagnet (SAF) structure, wherein the first spacer layer is comprised of a selected material with a selected thickness to allow an antiferromagnetic coupling between the first and second ferromagnetic layers of the first synthetic antiferromagnet (SAF) structure;

a second synthetic antiferromagnet (SAF) structure, comprising:

a third ferromagnetic layer;

a fourth ferromagnetic layer; and

a second spacer layer between the third and fourth ferromagnetic layers of the second synthetic antiferromagnet (SAF) structure, wherein the second spacer layer is comprised of a selected material with a selected thickness to allow an antiferromagnetic coupling between the third and fourth ferromagnetic layers of the second synthetic antiferromagnet (SAF) structure;

a first antiferromagnetic pinning layer disposed proximate to and coupled to the first synthetic antiferromagnet (SAF) structure;

a second antiferromagnetic pinning layer disposed proximate to and coupled to the second synthetic antiferromagnet (SAF) structure, such that the first and second synthetic antiferromagnet (SAF) structures are disposed between the first and second antiferromagnetic pinning layers, wherein the first and second antiferromagnetic layers are comprised of PtMn, wherein magnetic field directions in the first and second synthetic antiferromagnet pinning layers are annealed to be ninety degrees apart, wherein a magnetic field direction in the first antiferromagnetic pinning layer is annealed to be parallel with the magnetic field direction in the first synthetic antiferromagnet (SAF) structure, and wherein a magnetic field direction in the second antiferromagnetic pinning layer is annealed to be parallel with the magnetic field direction in the second synthetic antiferromagnet (SAF) structure;

a free layer structure disposed between the first and second synthetic antiferromagnet (SAF) structures;

a first nonmagnetic layer disposed between the first synthetic antiferromagnet (SAF) structure and the free layer structure;

a second nonmagnetic layer disposed between the second synthetic antiferromagnet (SAF) structure and the free layer structure, wherein a material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer to be greater than 0.5 nm while allowing a desired partial pinning between the second synthetic antiferromagnet (SAF) structure and the free layer structure; and

a temporary ferromagnetic layer disposed over and proximate to a selected one of the first antiferromagnetic pinning layer or the second antiferromagnetic pinning layer.

2. The magnetoresistance element of claim 1 , wherein the temporary ferromagnetic layer is comprised of CoFe.

3. The magnetoresistance element of claim 2 , wherein the temporary ferromagnetic layer has a thickness of about two nanometers before it is removed.

4. The magnetoresistance element of claim 1 , wherein the material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer of greater than 0.5 nm to allow a magnetic coupling between the second synthetic antiferromagnet (SAF) structure and the free layer structure to be between a maximum ferromagnetic coupling and a maximum antiferromagnetic coupling.

5. The magnetoresistance element of claim 1 , wherein the second nonmagnetic layer is comprised of a material selected to provide an adjustable RKKY coupling between the second synthetic antiferromagnet (SAF) structure and the free layer structure.

6. The magnetoresistance element of claim 1 , wherein the second nonmagnetic layer is comprised of Ru.

7. The magnetoresistance element of claim 6 , wherein a thickness of the second nonmagnetic layer is between about 0.5 nm and about 4.0 nm.

8. The magnetoresistance element of claim 6 , wherein a thickness of the second nonmagnetic layer is between about 2.0 nm and about 4.0 nm.

9. The magnetoresistance element of claim 6 , wherein a material and a thickness of the second nonmagnetic layer is selected to allow substantially zero magnetic coupling between the second synthetic antiferromagnet (SAF) structure and the free layer structure.

10. The magnetoresistance element of claim 6 , wherein the first nonmagnetic layer is comprised of Cu, Au or Ag.

11. The magnetoresistance element of claim 6 , wherein a thickness of the first nonmagnetic layer is between about 2.0 nm and about 3.0 nm.

12. The magnetoresistance element of claim 1 , wherein the magnetoresistance element comprises a spin valve.

13. The magnetoresistance element of claim 1 , wherein the magnetoresistance element comprises a GMR sensing element.

14. The magnetoresistance element of claim 1 , wherein the magnetoresistance element comprises a TMR sensing element.

15. The magnetoresistance element of claim 1 , wherein the free layer structure comprises first and second ferromagnetic free layers coupled together with no spacer layer between the first and second ferromagnetic free layers.

16. The magnetoresistance element of claim 1 , wherein the first ferromagnetic free layer is comprised of CoFe and the second ferromagnetic free layer is comprised of NiFe.

17. The magnetoresistance element of claim 1 , wherein the magnetoresistance element has a yoke shape.

18. The magnetoresistance element of claim 17 , wherein a length (L) of the yoke shape and a length (d) of lateral arms of the yoke shape are each at least three times a width (w) of the yoke shape, and the width (w) of the yoke shape is between about one μm and about twenty μm, wherein the length (L) is a longest dimension of the yoke shape.

19. A method of fabricating a magnetoresistance element, comprising

depositing the magnetoresistance element upon a substrate, the magnetoresistance element comprising:

a first synthetic antiferromagnet (SAF) structure, comprising:

a first ferromagnetic layer;

a second ferromagnetic layer; and

a spacer layer disposed between the first and second ferromagnetic layers of the first synthetic antiferromagnet (SAF) structure, wherein the spacer layer is comprised of a selected material with a selected thickness to allow an antiferromagnetic coupling between the first and second ferromagnetic layers of the first synthetic antiferromagnet (SAF) structure;

a second synthetic antiferromagnet (SAF) structure, comprising:

a third ferromagnetic layer;

a fourth ferromagnetic layer; and

a second spacer layer disposed between the third and fourth ferromagnetic layers of the second synthetic antiferromagnet (SAF) structure, wherein the second spacer layer is comprised of a selected material with a selected thickness to allow an antiferromagnetic coupling between the third and fourth ferromagnetic layers of the second synthetic antiferromagnet (SAF) structure;

as first antiferromagnetic pinning layer disposed proximate to and coupled to the first synthetic antiferromagnet (SAF) structure;

a second antiferromagnetic pinning layer disposed proximate to and coupled to the second synthetic antiferromagnet (SAF) structure, such that the first and second synthetic antiferromagnet (SAF) structures are disposed between the first and second antiferromagnetic pinning layers, wherein the first and second antiferromagnetic pinning layers are comprised of PtMn, wherein magnetic field directions in the first and second synthetic antiferromagnet pinning layers are annealed to be ninety degrees apart, wherein a magnetic field direction in the first antiferromagnetic pinning layer is annealed to be parallel with the magnetic field direction in the first synthetic antiferromagnet (SAF) structure, and wherein a magnetic field direction in the second antiferromagnetic pinning layer is annealed to be parallel with the magnetic field direction in the second synthetic antiferromagnet (SAF) structure;

a free layer structure disposed between the first and second synthetic antiferromagnet (SAF) structures;

a first nonmagnetic layer disposed between the first synthetic antiferromagnet (SAF) structure and the free layer structure;

a second nonmagnetic layer disposed between the second synthetic antiferromagnet (SAF) structure and the free layer structure, wherein a material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer to be greater than 0.5 nm while allowing a desired partial pinning between the second synthetic antiferromagnet (SAF) structure and the free layer structure; and

a temporary ferromagnetic layer disposed over and proximate to a selected one of the first antiferromagnetic pinning layer or the second antiferromagnetic pinning layer, the method further comprising:

removing the temporary ferromagnetic layer.

20. The method of claim 19 , wherein the temporary ferromagnetic layer is comprised of CoFe.

21. The method of claim 19 , wherein the temporary ferromagnetic layer has a thickness of about two nanometers before it is removed.

22. The method of claim 19 , wherein the removing comprises ion beam etching to remove the temporary ferromagnetic layer.

23. The method of claim 22 , wherein the ion beam etching comprises ion beam etching for a time period of about thirty seconds.

24. The method of claim 19 , wherein the material of the second nonmagnetic layer is selected to allow a thickness of the second nonmagnetic layer of greater than 0.5 nm to allow a magnetic coupling between the second synthetic antiferromagnet (SAF) structure and the free layer structure to be between a maximum ferromagnetic coupling and a maximum antiferromagnetic coupling.

25. The method of claim 19 , further comprising:

before the removing the temporary ferromagnetic layer:

annealing the first synthetic antiferromagnet (SAF) structure and the first antiferromagnetic pinning layer at a first annealing temperature, with a first annealing magnetic field, with a first annealing magnetic field direction, and with a first annealing duration; and

annealing the second synthetic antiferromagnet (SAF) structure and the second antiferromagnetic pinning layer at a second annealing temperature, with a second annealing magnetic field, with a second annealing magnetic field direction, and with a second annealing duration, wherein:

the first annealing magnate field direction is in a selected magnetization direction,

the second annealing magnetic field direction is orthogonal to the first annealing magnetic field direction, and

the first annealing magnetic field is higher than the second annealing magnetic field, wherein the second annealing magnetic field is selected to result in annealing of the second synthetic antiferromagnet (SAF) structure and annealing of the second antiferromagnetic pinning layer without affecting the annealing of the first synthetic antiferromagnet (SAF) structure or the annealing of the first antiferromagnetic pinning layer.

26. The method of claim 25 , wherein the first and second synthetic antiferromagnet (SAF) structures are both comprised of two or more CoFe layers.

27. The method of claim 25 , wherein the first annealing magnetic field is about one Tesla, and wherein the second annealing magnetic field is about 0.12 Tesla.

28. The method of claim 27 , wherein the first annealing temperature is about two hundred ninety five degrees Celsius, wherein the second annealing temperature is about three hundred degrees Celsius, and wherein the first annealing duration is about one hour and the second annealing duration is about one hour.

29. The method of claim 19 , wherein a thickness of the second nonmagnetic layer is between about 0.5 nm and about 4 nm.

30. The method of claim 19 , wherein the second nonmagnetic layer is comprised of a material selected to provide an adjustable RKKY coupling between the first synthetic antiferromagnet (SAF) structure and the free layer structure.

31. The method of claim 19 , wherein the second nonmagnetic layer is comprised of Ru.

32. The method of claim 19 , further comprising

patterning at least a portion of the magnetoresistance element in a yoke shape.

33. The method of claim 32 , wherein a length (L) of the yoke shape and a length (d) of lateral arms of the yoke shape are each at least three times a width (w) of the yoke shape, and the width (w) of the yoke shape is between about one μm and about twenty μm, wherein the length (L) is a longest dimension of the yoke shape.

34. The method of claim 19 , further comprising:

depositing a cap layer over a selected one of the first or second antiferromagnetic pinning layer after the removing;

patterning at least a portion of the magnetoresistance element in a yoke shape.

35. The method of claim 34 , wherein a length (L) of the yoke shape and a length (d) of the lateral arms of the yoke shape are each at least three times a width (w) of the yoke shape, and the width (w) of the yoke shape is between about one μm and about twenty μm, wherein the length (L) is a longest dimension of the yoke shape.