Magnetic element having reduced current density
View Patent ↗A memory device includes a fixed magnetic layer, a tunnel barrier layer over the fixed magnetic layer, and a free magnetic structure formed over the tunnel barrier layer, wherein the free magnetic structure has layers or sub-layers that are weakly magnetically coupled. Thus, a low programming voltage can be used to avoid tunnel barrier breakdown, and a small pass transistor can be used to save die real estate.
1. A memory device comprising:
a fixed magnetic layer;
a tunnel barrier layer over the fixed magnetic layer; and
a free magnetic structure formed over the tunnel barrier layer, wherein the free magnetic structure comprises:
a first free magnetic layer having a first magnetic moment;
a first interlayer in contact with the first free magnetic layer and having a thickness of less than 2.0 nanometers; and
a second free magnetic layer having a second magnetic moment, wherein the second free magnetic layer is weakly magnetically coupled to the first free magnetic layer and is in contact with the first interlayer; and wherein:
the memory device is capable of being programmed by impinging a spin-polarized electron current on the free magnetic structure, thereby causing the first and second magnetic moments to be sequentially switched due to being weakly ferromagnetically coupled.
2. The memory device of claim 1 , wherein the magnetic coupling strength has a magnitude is between 50 Oersteds to 500 Oersteds.
3. The memory device of claim 2 , wherein the first interlayer comprises an element selected from the group consisting of Ru, Rh, Os, and Re and wherein the first interlayer has a thickness in the range of approximately 1.2 to approximately 1.7 nanometers.
4. The memory device of claim 1 , wherein the first interlayer comprises an insulating material.
5. The memory device of claim 4 , wherein the first interlayer comprises an oxide comprising an element selected from the group consisting of Si, Mg, Al, Ti, Ta, Hf, Fe, Ni, Co, V, and Zr.
6. The memory device of claim 1 , wherein the first interlayer comprises a conductive material.
7. The memory device of claim 6 , wherein the first interlayer comprises a metal comprising an element selected from the group consisting of Ta, Ti, Mg, Hf, Al, Ru, Os, Re, Rh, V, Cu and B.
8. The memory device of claim 1 , wherein the first interlayer has a thickness in the range of approximately 0.1 to approximately 1 nm.
9. The memory device of claim 2 , wherein the magnetic coupling is ferromagnetic.
10. The memory device of claim 1 , wherein the magnetic coupling is antiferromagnetic.
11. The memory device of claim 3 , wherein the first interlayer comprises an element selected from the group consisting of Ru, Rh, Os, and Re and wherein the first interlayer has a thickness in the range of approximately 0.5 to approximately 1.2 nanometers.