Precessional spin current structure for MRAM
A magnetoresistive random-access memory (MRAM) is disclosed. MRAM device has a magnetic tunnel junction stack having a significantly improved performance of the free layer in the magnetic tunnel junction structure. The MRAM device utilizes a precessional spin current (PSC) magnetic layer in conjunction with a perpendicular MTJ where the in-plane magnetization direction of the PSC magnetic layer is free to rotate.
1. A magnetic device, comprising
a synthetic antiferromagnetic structure in a first plane, the synthetic antiferromagnetic structure including a magnetic reference layer, the magnetic reference layer having a magnetization vector that is perpendicular to the first plane and having a fixed magnetization direction;
a non-magnetic tunnel barrier layer in a second plane and disposed over the magnetic reference layer;
a free magnetic layer in a third plane and disposed over the non-magnetic tunnel barrier layer, the free magnetic layer having a magnetization vector that is perpendicular to the third plane and having a magnetization direction that precesses from a first magnetization direction to a second magnetization direction when a spin-polarized current passes there through, the magnetic reference layer, the non-magnetic tunnel barrier layer and the free magnetic layer forming a magnetic tunnel junction;
a non-magnetic spacer in a fourth plane and disposed over the free magnetic layer;
precessional spin current means in a fifth plane for causing a magnetization vector with a magnetization component in the fifth plane of the precessional spin current means to follow precession of the magnetization direction of the free magnetic layer, the precessional spin current means being physically separated from the free magnetic layer and electronically coupled to the free magnetic layer by the non-magnetic spacer, wherein rotation of the magnetization component in the fifth plane of the precessional spin current means causes spin polarization of electrons of electrical current passing there through to change in a manner corresponding to the magnetic vector in the fifth plane of the precessional spin current means, thereby creating the spin-polarized current, the spin-polarized current causing spin transfer torque to assist switching of the magnetization vector of the free magnetic layer, the free magnetic layer storing a memory value.
2. The magnetic device of claim 1 wherein the precessional spin current means has a circular shape.
3. The magnetic device of claim 1 wherein a magnetization direction of the magnetization vector of the precessional spin current means is in the fifth plane of the precessional spin current means.
4. The magnetic device of claim 1 wherein a magnetization direction of the precessional spin current means has the magnetization component in the fifth plane of the precessional spin current means that freely rotates in the fifth plane.
5. The magnetic device of claim 1 wherein the precessional spin current means comprises CoFeB.
6. The magnetic device of claim 1 wherein the precessional spin current means is magnetically coupled to the free magnetic layer.
7. The magnetic device of claim 1 wherein precession of the magnetization vector with the magnetization component in the fifth plane of the precessional spin current means is synchronized to precession of the free magnetic layer.
8. The magnetic device of claim 1 wherein the magnetization vector with the magnetization component in the fifth plane of the precessional spin current means has a rotation frequency greater than zero.
9. The magnetic device of claim 1 , further comprising a current source that directs the electrical current through the precessional spin current means, the non-magnetic spacer, the free magnetic layer, the non-magnetic tunnel barrier layer, and the magnetic reference layer, wherein the electrons of the electrical current are aligned in a magnetic direction of the precessional spin current means.
10. A magnetic device, comprising:
a magnetic tunnel junction in a first plane comprising a free magnetic layer and a reference magnetic layer, the free magnetic layer and the reference magnetic layer separated by a non-magnetic tunneling barrier layer, the free magnetic layer having a magnetization vector that is perpendicular to the first plane and having a magnetization direction that precesses when a spin-polarized current passes there through from a first magnetization direction to a second magnetization direction;
a non-magnetic spacer in a second plane disposed over the free magnetic layer;
a precessional spin current means in a third plane for causing a magnetization vector with a magnetization component in the third plane of the precessional spin current means to follow precession of the magnetization direction of the free magnetic layer upon application of a current to the magnetic device, wherein the magnetization component in the third plane of the precessional spin current means freely rotates in any magnetic direction in the third plane, the precessional spin current means being electronically coupled through the non-magnetic spacer to the free magnetic layer, the precessional spin current means separated from the free magnetic layer by the non-magnetic spacer, wherein rotation of the magnetization component in the third plane of the precessional spin current means causes spin polarization of electrons of the current passing there through via the magnetic device to change in a manner corresponding to the magnetization vector of the precessional spin current means, thereby creating the spin-polarized current, the spin-polarized current thereby causing spin transfer torque to assist switching of the magnetization vector of the free magnetic layer, the free magnetic layer storing a memory value.
11. The magnetic device of claim 10 wherein the precessional spin current means has a circular shape.
12. The magnetic device, of claim 10 wherein a magnetization direction of the magnetization vector of the precessional spin current means is in the third plane of the precessional spin current means.
13. The magnetic device of claim 10 wherein a magnetization direction of the magnetization vector of the precessional spin current means has the magnetization component in the third plane which freely rotates in the third plane of the precessional spin current means.
14. The magnetic device of claim 10 wherein the precessional spin current means comprises CoFeB.
15. The magnetic device of claim 10 wherein the precessional spin current means is magnetically coupled to the free magnetic layer.
16. The magnetic device of claim 10 wherein precession of the magnetization vector with the magnetization component in the third plane of the precessional spin current means is synchronized to precession of the free magnetic layer.
17. The magnetic device of claim 10 wherein the magnetization vector with the magnetization component in the third plane of the precessional spin current means has a rotation frequency greater than zero.