Low current switching magnetic tunnel junction design for magnetic memory using domain wall motion
View Patent ↗A multi-state low-current-switching magnetic memory element (magnetic memory element) comprising a free layer, two stacks, and a magnetic tunneling junction is disclosed. The stacks and magnetic tunneling junction are disposed upon surfaces of the free layer, with the magnetic tunneling junction located between the stacks. The stacks pin magnetic domains within the free layer, creating a free layer domain wall. A current passed from stack to stack pushes the domain wall, repositioning the domain wall within the free layer. The position of the domain wall relative to the magnetic tunnel junction corresponds to a unique resistance value, and passing current from a stack to the magnetic tunnel junction reads the magnetic memory element's resistance. Thus, unique memory states may be achieved by moving the domain wall.
1. A multi-state low-current switching magnetic memory element comprising:
a free layer having at least one surface;
a first stack extending from a surface of the free layer;
a second stack extending from a surface of the free layer;
a magnetic tunneling junction (MTJ) extending from a surface of the free layer between said first stack and said second stack;
wherein the first stack and the second stack pin opposing magnetic moments within the free layer, creating two unique magnetic domains within the free layer; and
the magnetic domains within the free layer are separated by a domain wall.
2. The multi-state low-current switching magnetic memory element of claim 1 , wherein the first and second stacks each comprise at least a fixed layer and an anti-ferromagnetic layer, wherein the anti-ferromagnetic layer is disposed upon the fixed layer.
3. The multi-state low-current switching magnetic memory element of claim 1 , wherein the magnetic tunneling junction comprises at least a tunnel barrier layer, a fixed layer, and an anti-ferromagnetic layer, wherein the anti-ferromagnetic layer is disposed upon the fixed layer.
4. The multi-state low-current switching magnetic memory element of claim 3 , wherein the tunnel barrier layer of the magnetic tunneling junction is disposed upon a surface of the free layer.
5. The multi-state low-current switching magnetic memory element of claim 4 , wherein a fixed layer is disposed upon said tunnel barrier layer of the magnetic tunneling junction.
6. The multi-state low-current switching magnetic memory element of claim 5 , wherein the cross-sectional area of the free layer is about 500 nm 2 to 25,000 nm 2 .
7. The multi-state low-current switching magnetic memory element of claim 6 , wherein the position of said domain wall within the free layer is dynamic.
8. The multi-state low-current switching magnetic memory element of claim 7 , wherein the domain wall is pushed through the free layer by electron current passed between the first and second stacks.
9. The multi-state low-current switching magnetic memory element of claim 8 , wherein the position of the domain wall relative to the magnetic tunneling junction corresponds to different memory states.
10. The multi-state low-current switching magnetic memory element of claim 9 , wherein electron current passed between the first stack and the magnetic tunneling junction, or the second stack and the magnetic tunneling junction, provides a reading of the domain wall position.
11. The multi-state low-current switching magnetic memory element of claim 10 , wherein the reading of the domain wall position is a resistance value.
12. The multi-state low-current switching magnetic memory element of claim 11 , wherein different resistance values correspond to different memory states.
13. The multi-state low-current switching magnetic memory element of claim 12 , wherein the free layer structure generally resembles a rectangular extrusion.
14. The multi-state low-current switching magnetic memory element of claim 13 , wherein the first stack, second stack, and magnetic tunneling junction each extend from any of the four surfaces of the free layer having a substantially identical dimension.