Magnetic memory with strain-assisted exchange coupling switch
View Patent ↗A magnetic tunnel junction cell having a free layer and first pinned layer with perpendicular anisotropy, the cell including a coupling layer between the free layer and a second pinned layer, the coupling layer comprising a phase change material switchable from an antiferromagnetic state to a ferromagnetic state. In some embodiments, at least one actuator electrode proximate the coupling layer transfers a strain from the electrode to the coupling layer to switch the coupling layer from the antiferromagnetic state to the ferromagnetic state. Memory devices and methods are also described.
1. A magnetic tunnel junction cell comprising:
a first ferromagnetic pinned layer, a ferromagnetic free layer, and a non-magnetic barrier layer therebetween, the first pinned layer and the free layer each having an out-of-plane magnetization orientation,
a second ferromagnetic pinned layer and a coupling layer between the second pinned layer and the free layer, the coupling layer comprising a phase change material that facilitates switching of the ferromagnetic free layer.
2. The magnetic tunnel junction of claim 1 , wherein the phase change material of the coupling layer facilitates switching of the ferromagnetic free layer upon its phase change.
3. The magnetic tunnel junction of claim 1 , wherein the phase change material comprises antiferromagnetic material or superparamagnetic phase transition material.
4. The magnetic tunnel junction of claim 1 , wherein the phase change material comprises FeRh or ternary alloys thereof.
5. The magnetic tunnel junction cell of claim 1 , wherein the second pinned layer has an in-plane magnetization orientation.
6. The magnetic tunnel junction cell of claim 1 , wherein the coupling layer is adjacent to both the free layer and the second pinned layer.
7. The magnetic tunnel junction cell of claim 1 further comprising a first electrode and a second electrode electrically connected to pass a current through at least the free layer and the first pinned layer.
8. The magnetic tunnel junction cell of claim 1 further comprising at least one actuator electrode proximate the coupling layer.
9. The magnetic tunnel junction cell of claim 8 wherein the at least one actuator electrode comprises a piezoelectric material.
10. The magnetic tunnel junction cell of claim 9 wherein the piezoelectric material comprises lead zirconate titanate.
11. The magnetic tunnel junction of claim 1 further comprising a first actuator electrode and a second actuator electrode.
12. A memory device comprising:
a magnetic tunnel junction cell comprising a first ferromagnetic pinned layer, a ferromagnetic free layer, and a non-magnetic barrier layer therebetween, the first pinned layer and the free layer each having an out-of-plane magnetization orientation, the magnetic tunnel junction cell further comprising a second ferromagnetic pinned layer and a coupling layer between the second pinned layer and the free layer, the coupling layer comprising a phase change material that facilitates switching of the ferromagnetic free layer, and the second pinned layer has an in-plane magnetization orientation;
a first electrode and a second electrode electrically connected to the magnetic tunnel junction cell to pass a current therethrough;
at least one actuator electrode proximate the coupling layer; and
a voltage source electrically connected to the at least one actuator electrode.
13. The memory device of claim 12 wherein the voltage source, when activated, induces a nano-mechanical strain in the at least one actuator electrode.
14. The memory device of claim 12 further comprising a timing circuit operably connected to the voltage source.
15. The memory device of claim 12 wherein a write voltage passed through the first and second electrodes is coincident with a voltage through the at least one actuator electrode.
16. The magnetic tunnel junction of claim 12 , wherein the phase change material comprises antiferromagnetic material or superparamagnetic phase transition material.
17. The magnetic tunnel junction of claim 16 , wherein the phase change material comprises FeRh or ternary alloys thereof.
18. A magnetic element comprising:
a first ferromagnetic pinned layer, a ferromagnetic free layer, and a non-magnetic barrier layer therebetween, the first pinned layer and the free layer each having an out-of-plane magnetization orientation,
a second ferromagnetic pinned layer and a coupling layer between the second pinned layer and the free layer, the coupling layer comprising a phase change material that facilitates switching of the ferromagnetic free layer, and the second pinned layer has an in-plane magnetization orientation.
19. The magnetic element of claim 18 , wherein the coupling layer comprises FeRh.
20. The magnetic element of claim 18 , wherein the coupling layer is adjacent to both the free layer and the second pinned layer.