Non-volatile memory with stray magnetic field compensation
View Patent ↗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 memory cell comprising:
a reference structure having a perpendicular anisotropy and a first magnetization direction;
a recording structure having a perpendicular anisotropy;
a tunneling barrier disposed between the reference structure and the recording structure;
a compensation layer having a perpendicular anisotropy and a second magnetization direction;
a nonmagnetic spacer layer disposed between the compensation layer and the recording structure; and
a spin polarizing layer disposed between the reference structure and the recording structure.
2. The memory cell of claim 1 , wherein the spin polarizing layer separates the reference structure from the recording structure.
3. The memory cell of claim 1 , wherein the spin polarizing layer separates the reference structure from the tunnel barrier.
4. The memory cell of claim 1 , wherein the spin polarizing layer separates the recording structure from the tunnel barrier.
5. The memory cell of claim 1 , further comprising a second spin polarizing layer separating the reference structure from the recording structure.
6. The memory cell of claim 5 , wherein the spin polarizing layer separates the reference structure from the tunnel barrier and the second spin polarizing layer separates the recording structure from the tunnel barrier.
7. The memory cell of claim 1 , wherein the compensation layer cancels a stray magnetic field generated by the reference structure.
8. The memory cell of claim 1 , wherein the first and second magnetization directions oppose each other.
9. The memory cell of claim 1 , wherein the first and second magnetization directions are non-normal.
10. The 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.
11. The 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.
12. The memory cell of claim 1 , wherein the nonmagnetic spacer layer comprises a second tunneling barrier layer.
13. The memory cell of claim 1 , wherein the compensation layer generates no spin momentum or tunneling magnetoresistive (TMR) effect.
14. A memory cell comprising:
a reference structure having a perpendicular anisotropy and a first magnetization direction;
a recording structure having a perpendicular anisotropy;
a tunneling barrier disposed between the reference structure and the recording structure;
a compensation layer having a perpendicular anisotropy and a second magnetization direction;
a nonmagnetic spacer layer disposed between the compensation layer and the recording structure; and
a spin polarizing layer disposed between the reference structure and the recording structure;
wherein, the first or second magnetization directions are non-normal.
15. The memory cell of claim 14 , wherein the reference structure comprises a spin polarizing layer.
16. The memory cell of claim 15 , wherein the recording structure comprises a spin polarizing layer.
17. The memory cell of claim 14 , wherein the compensation layer cancels a stray magnetic field generated by the reference structure.
18. The memory cell of claim 11 , wherein the first and second magnetization directions oppose each other.
19. The 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.
20. The memory cell of claim 11 , wherein the first magnetization direction is non-normal and the second magnetic direction is non-normal.