Non-volatile memory with stray magnetic field compensation
A method and apparatus for stray magnetic field compensation in a non-volatile memory cell, such as a spin-torque transfer random access memory (STRAM). In some embodiments, a first tunneling barrier is coupled to a reference structure that has a perpendicular anisotropy and a first magnetization direction. A recording structure that has a perpendicular anisotropy is coupled to the first tunneling barrier and a nonmagnetic spacer layer. A compensation layer that has a perpendicular anisotropy and a second magnetization direction in substantial opposition to the first magnetization direction is coupled to the nonmagnetic spacer layer. Further, the memory cell is programmable to a selected resistance state with application of a current to the recording structure.
1. A spin-torque transfer memory cell comprising:
a first tunneling barrier;
a reference structure coupled to the first tunneling barrier, the reference structure having a perpendicular anisotropy and a first magnetization direction;
a nonmagnetic spacer layer;
a recording structure disposed between the first tunneling barrier and nonmagnetic spacer layer, the recording structure having a perpendicular anisotropy; and
a compensation layer coupled to the nonmagnetic spacer layer, the compensation layer having a perpendicular anisotropy and a second magnetization direction.
2. The spin-torque transfer memory cell of claim 1 , wherein the reference structure comprises a spin polarizing layer.
3. The spin-torque transfer memory cell of claim 1 , wherein the compensation layer cancels a stray magnetic field generated by the reference structure.
4. The spin-torque transfer memory cell of claim 1 , wherein the first and second magnetization directions oppose each other.
5. The spin-torque transfer memory cell of claim 1 , wherein the first and second magnetization directions are non-normal.
6. The spin-torque transfer memory cell of claim 1 , wherein either the first magnetization direction is non-normal while the second magnetization direction is normal or the second magnetic direction is non-normal while the first magnetic direction is normal.
7. The spin-torque transfer memory cell of claim 1 , wherein the nonmagnetic spacer layer comprises a metallic material whose band structure matches either the majority or minority electron band of the compensation layer.
8. The spin-torque transfer memory cell of claim 1 , wherein the nonmagnetic spacer layer comprises a second tunneling barrier layer.
9. The spin-torque transfer memory cell of claim 1 , wherein the compensation layer generates no spin momentum or tunneling magnetoresistive (TMR) effect.
10. The spin-torque transfer memory cell of claim 1 , wherein the recording structure comprises a spin polarizing layer.
11. A spin-torque transfer memory cell comprising:
a first tunneling barrier;
a reference structure coupled to the first tunneling barrier, the reference structure having a perpendicular anisotropy and a first magnetization direction;
a nonmagnetic spacer layer;
a recording structure disposed between the first tunneling barrier and nonmagnetic spacer layer, the recording structure having a perpendicular anisotropy; and
a compensation layer coupled to the nonmagnetic spacer layer, the compensation layer having a perpendicular anisotropy and a second magnetization direction;
wherein, the first or second magnetization directions are non-normal.
12. The spin-torque transfer memory cell of claim 11 , wherein the reference structure comprises a spin polarizing layer.
13. The spin-torque transfer memory cell of claim 12 , wherein the recording structure comprises a spin polarizing layer.
14. The spin-torque transfer memory cell of claim 11 , wherein the compensation layer cancels a stray magnetic field generated by the reference structure.
15. The spin-torque transfer memory cell of claim 11 , wherein the first and second magnetization directions oppose each other.
16. The spin-torque transfer memory cell of claim 11 , wherein the first and second magnetization directions are non-normal.
17. The spin-torque transfer memory cell of claim 11 , wherein either the first magnetization direction is non-normal while the second magnetization direction is normal or the second magnetic direction is non-normal while the first magnetic direction is normal.
18. The spin-torque transfer memory cell of claim 11 , wherein the nonmagnetic spacer layer comprises a metallic material whose band structure matches either the majority or minority electron band of the compensation layer.
19. The spin-torque transfer memory cell of claim 11 , wherein the nonmagnetic spacer layer comprises a second tunneling barrier layer.
20. The spin-torque transfer memory cell of claim 11 , wherein the reference structure has a first magnetic field that is greater than a second magnetic field of the compensation layer.