Unidirectional spin torque transfer magnetic memory cell structure
View Patent ↗Spin torque transfer magnetic random access memory devices configured to be programmed unidirectionally and methods of programming such devices. The devices include memory cells having two pinned layers and a free layer therebetween. By utilizing two pinned layers, the spin torque effect on the free layer from each of the two pinned layers, respectively, allows the memory cells to be programmed with unidirectional currents.
1. A memory cell comprising:
a top pinned layer;
a bottom pinned layer;
a free layer arranged between the top pinned layer and the bottom pinned layer; and
a heat generating layer coupled directly to the bottom pinned layer, wherein the heat generating layer is configured to alter a magnetization of the bottom pinned layer upon activation.
2. The memory cell, as set forth in claim 1 , wherein each of the top pinned layer, the bottom pinned layer and the free layer are ferromagnetic.
3. The memory cell, as set forth in claim 1 , wherein the top pinned layer and the bottom pinned layer are magnetized in the same direction.
4. The memory cell, as set forth in claim 1 , further comprising:
a top nonmagnetic layer formed between the top pinned layer and the free layer; and
a bottom nonmagnetic layer formed between the free layer and the bottom pinned layer.
5. The memory cell, as set forth in claim 1 , further comprising an antiferromagnetic layer coupled directly to the heat generating layer.
6. The memory cell, as set forth in claim 1 , further comprising a magnetic tunnel junction formed on the top pinned layer.
7. The memory cell, as set forth in claim 6 , comprising an antiferromagnetic layer arranged between the magnetic tunnel junction and the top pinned layer.
8. The memory cell, as set forth in claim 6 , comprising a spin randomization separation layer arranged between the magnetic tunnel junction and the top pinned layer.
9. The memory cell, as set forth in claim 6 , wherein the magnetic tunnel junction is magnetostatically coupled to the free layer.
10. The memory cell, as set forth in claim 6 , wherein the magnetic tunnel junction comprises:
a sensing free layer;
a sensing pinned layer; and
a nonmagnetic barrier layer disposed between the sensing free layer and the sensing pinned layer.
11. The memory cell, as set forth in claim 10 , wherein the magnetic tunnel junction is magnetostatically coupled to the free layer, such that changing the magnetization of the free layer will change the magnetization of the sensing free layer.
12. The memory cell, as set forth in claim 1 , wherein the free layer comprises a synthetic free layer.
13. The memory cell, as set forth in claim 1 , wherein the top pinned layer comprises a synthetic pinned layer.
14. The memory cell, as set forth in claim 1 , wherein each of the top pinned layer, the free layer and the bottom pinned layer is ferromagnetic, and wherein a magnetization of at least one of the top pinned layer, the free layer and the bottom pinned layer is in a direction perpendicular to a layer plane.
15. The memory cell, as set forth in claim 14 , wherein a magnetization of each of the top pinned layer, the free layer and the bottom pinned layer is in a direction perpendicular to a layer plane.
16. A memory cell comprising a sensing structure comprising:
a heat generating layer;
a bottom pinned ferromagnetic layer formed on the heat generating layer, wherein the heat generating layer is configured to alter a magnetization of the bottom pinned ferromagnetic layer when activated;
a bottom nonmagnetic layer formed on the bottom pinned ferromagnetic layer;
a free ferromagnetic layer formed on the bottom nonmagnetic layer;
a top nonmagnetic layer formed on the free ferromagnetic layer; and
a top pinned ferromagnetic layer formed on the top nonmagnetic layer.
17. The memory cell, as set forth in claim 16 , wherein the top pinned ferromagnetic layer and the bottom pinned ferromagnetic layer are magnetized in the same direction.
18. The memory cell, as set forth in claim 16 , further comprising a magnetic tunnel junction formed on the top pinned layer, wherein the magnetic tunnel junction comprises:
a sensing free layer;
a nonmagnetic barrier layer formed on the sensing free layer; and
a sensing pinned layer formed on the nonmagnetic barrier layer, and
wherein the sensing free layer is arranged between the sensing pinned layer and the top pinned ferromagnetic layer.
19. The memory cell, as set forth in claim 18 , further comprising a nonmagnetic spacer layer formed between the top pinned ferromagnetic layer and the sensing pinned layer, wherein the top pinned ferromagnetic layer, the nonmagnetic spacer layer and the sensing pinned layer form a synthetic pinned ferromagnetic layer.
20. The memory cell, as set forth in claim 19 , wherein the top pinned ferromagnetic layer and the sensing pinned layer are magnetized in opposite directions.
21. The memory cell, as set forth in claim 16 , wherein the free ferromagnetic layer is a synthetic layer comprising:
a top free ferromagnetic layer;
a bottom free ferromagnetic layer; and
a nonmagnetic coupling layer formed therebetween.
22. The memory cell, as set forth in claim 16 , wherein the top pinned ferromagnetic layer is a synthetic layer comprising:
an upper top free ferromagnetic layer;
a lower top free ferromagnetic layer; and
a nonmagnetic coupling layer formed therebetween.
23. The memory cell, as set forth in claim 16 , wherein a magnetization of at least of the top pinned ferromagnetic layer, the free ferromagnetic layer and the bottom pinned ferromagnetic layer is in a direction perpendicular to a layer plane.