Spin based device with low transmission barrier

1. A spin-based device including a thin film stack comprising:

i) a first ferromagnetic layer characterized by a first coercivity and a first magnetization that is responsive to a switching magnetic field imposed on the spin-based device;

ii) a second ferromagnetic layer characterized by a second magnetization and a second coercivity which is substantially greater than said first coercivity, such that said second magnetization does not change in response to said switching magnetic field;

wherein an impedance of the spin-based device to a spin based current varies in accordance with a magnetization orientation relationship between said first ferromagnetic layer and said second ferromagnetic layer;

iii) a third layer including at least one of gold, silver, aluminum and/or copper situated between said first ferromagnetic layer and said second ferromagnetic layer;

iv) a fourth layer located in said thin film stack which is adapted to promote isotropic flow for said spin based current.

2. The spin-based device of claim 1 , wherein at least one of said first ferromagnetic layer and said second ferromagnetic layer comprises a multi-layer of two different materials.

3. The spin-based device of claim 1 , wherein the device is characterized by a transimpedance value which increases as dimensions of said device decrease.

4. The spin-based device of claim 1 , wherein said fourth layer includes at least one of gold, silver, aluminum and/or copper.

5. The spin based device of claim 1 , further including a low transmission barrier layer situated between said first ferromagnetic layer and said second ferromagnetic layer.

6. The spin based device of claim 5 , wherein said low transmission barrier is at an interface or a boundary of said third layer.

7. The spin based device of claim 1 wherein said third layer is a paramagnetic material.

8. The spin based device of claim 1 wherein said third layer includes copper and is less than approximately 1 micron in thickness.

9. The spin based device of claim 1 wherein said first coercivity is less than half of said second coercivity.

10. The spin based device of claim 1 further including a fifth layer including at least one of gold, silver, aluminum and/or copper situated near said first ferromagnetic layer and which is adapted to improve current flow and protect against oxidation of such ferromagnetic layer.

11. The spin based device of claim 1 , wherein said device is situated on a silicon substrate.

12. The spin based device of claim 1 , wherein said spin based current flows perpendicular to a magnetization plane of said first ferromagnetic layer and said second ferromagnetic layer.

13. A spin-based device including a thin film stack comprising:

i) a first ferromagnetic layer characterized by a first coercivity;

ii) a second ferromagnetic layer characterized by a second coercivity which is substantially greater than said first coercivity;

iii) a third layer including at least one of gold, silver, aluminum and/or copper situated between said first ferromagnetic layer and said second ferromagnetic layer;

iv) a fourth layer located in the thin film stack which is adapted as a low transmission barrier to a spin based current.

14. The spin-based device of claim 13 , wherein said first coercivity is less than half of said second coercivity.

15. The spin-based device of claim 14 , wherein said first coercivity is less than 10 oersteds.

16. The spin-based device of claim 13 wherein an amplitude of a switching field used to change a first magnetization of said first ferromagnetic layer is about 10 oersteds, and said second ferromagnetic layer has a second magnetization which does not change in response to said switching field.

17. The spin-based device of claim 13 , further including a fifth layer located in the thin film stack adapted to promote magnetic anisotropy in said second ferromagnetic layer.

18. The spin-based device of claim 13 , further including a fifth layer located in said thin film stack adapted to promote isotropic current flow.

19. The spin based device of claim 15 , further including a nickel oxide layer situated on said second ferromagnetic layer.

20. The spin based device of claim 13 , wherein said low transmission barrier is at an interface or a boundary of said third layer.

21. The spin based device of claim 13 , further including a fifth layer located in the thin film stack which is adapted as a second low transmission barrier to a spin based current.

22. The spin based device of claim 13 further including a fifth layer layer including at least one of gold, silver, aluminum and/or copper which is situated on said first ferromagnetic layer.

23. The spin based device of claim 22 , wherein said fifth layer is adapted to improve current flow and protect against oxidation of such ferromagnetic layer.

24. The spin based device of claim 13 , wherein said spin based current flows perpendicular to a magnetization plane of said first ferromagnetic layer and said second ferromagnetic layer.

25. The spin based device of claim 13 , wherein said device is situated on an insulator.

26. The spin based device of claim 25 , wherein said insulator is situated on a silicon substrate.

27. The spin based device of claim 26 , further including one or more semiconducting devices in said silicon substrate.

28. A spin-based device configured as a thin film stack comprising:

i) a first ferromagnetic layer with a first variable magnetization state which can be changed in response to a magnetic field;

ii) a second layer including at least one of gold, silver, aluminum and/or copper which is adapted for preventing oxidation and enhancing current flow in said first ferromagnetic layer;

iii) a second ferromagnetic layer with a second magnetization state which is fixed;

iv) a fourth layer including at least one of gold, silver, aluminum and/or copper situated between said first ferromagnetic layer and said second ferromagnetic layer;

v) a fifth layer in the thin film stack which is adapted as a low transmission barrier to a spin based current.

29. The spin based device of claim 28 , wherein said device is situated on an insulator.

30. The spin based device of claim 29 , wherein said insulator is situated on a silicon substrate.

31. The spin based device of claim 30 , further including one or more semiconducting devices in said silicon substrate.

32. The spin based device of claim 28 , further including a sixth layer adapted to promote isotropic current flow in said second ferromagnetic layer.

33. The spin based device of claim 28 , further including a sixth layer adapted to promote magnetic anisotropy in said second ferromagnetic layer.

34. The spin based device of claim 28 , further including a nickel oxide layer situated on said second ferromagnetic layer.

35. A spin-based device including a thin film stack comprising:

i) a first ferromagnetic layer characterized by a first coercivity;

ii) a second ferromagnetic layer characterized by a second coercivity which is substantially greater than said first coercivity;

iii) a third layer situated between said first ferromagnetic layer and said second ferromagnetic layer and adapted as a low transmission barrier to a spin based current;

iv) a fourth layer situated in said thin film stack so as to promote magnetic anisotropy in said second ferromagnetic layer.

36. The spin based device of claim 35 further including an oxidation protection layer that also enhances current flow in said first ferromagnetic layer.

37. The spin based device of claim 35 further including a fifth layer located in said thin film stack which is adapted as a second low transmission barrier.

38. The spin based device of claim 35 wherein said low transmission barrier is situated at an interface of at least one of said first ferromagnetic layer and said second ferromagnetic layer.

39. The spin-based device of claim 35 , wherein at least one of said first ferromagnetic layer and said second ferromagnetic layer comprises a bi-layer of two different materials.

40. The spin-based device of claim 35 , wherein the device is characterized by a transimpedance value which increases as dimensions of said device decrease.

41. The spin-based device of claim 35 , wherein said third layer further includes a base layer comprised of at least one of gold, silver, aluminum and/or copper.

42. The spin based device of claim 35 wherein said first coercivity is less than half of said second coercivity.

43. The spin based device of claim 35 , wherein said device is situated on an insulator.

44. The spin based device of claim 43 , wherein said insulator is situated on a silicon substrate.

45. The spin based device of claim 44 , further including one or more semiconducting devices in said silicon substrate.

46. The spin based device of claim 35 , wherein said spin based current flows perpendicular to a magnetization plane of said first ferromagnetic layer and said second ferromagnetic layer.

47. A spin-based device including a thin film stack comprising:

i) a first ferromagnetic layer with a first coercivity and a variable magnetization state that can be altered in response to a magnetic field;

ii) a second ferromagnetic layer with a second coercivity which is substantially greater than said first coercivity and having a fixed magnetization state;

iv) a third layer situated in said thin film stack so as to promote magnetic anisotropy in said second ferromagnetic layer;

iii) a fourth layer situated at an interface to said first ferromagnetic layer and/or said second ferromagnetic layer and adapted as a low transmission barrier to a spin based current;

wherein a value of an impedance in the spin based device for said spin polarized current flowing through the stack varies in accordance with a relationship between said first changeable magnetization state and said second non-changeable magnetization state.

48. The spin-based device of claim 47 , wherein a coupling parameter α=H/I is configured to be between 5 and 20.

49. The spin based device of claim 47 further including a fifth layer located in said thin film stack which is adapted as a second low transmission barrier.

50. The spin based device of claim 47 , wherein said device is situated on an insulator.

51. The spin based device of claim 50 , wherein said insulator is situated on a silicon substrate.

52. The spin based device of claim 51 , further including one or more semiconducting devices in said silicon substrate.