Three terminal SOT memory cell with anomalous hall effect
View Patent ↗A method and apparatus for deterministically switching a free layer in a spin orbit torque magnetoresistive random access memory (SOT-MRAM) cell is disclosed herein. In one embodiment, an SOT-MRAM memory cell is provided. The SOT-MRAM memory cell includes a magnetic tunnel junction, a ferromagnetic bias layer, and an antiferromagnetic layer. The magnetic tunnel junction includes a free layer having primarily two bi-stable magnetization directions, a reference layer having a fixed magnetization direction, and an insulating tunnel barrier layer positioned between the free layer and the reference layer. The ferromagnetic bias layer is configured to provide spin orbit torque via anomalous Hall effect and simultaneously configured to provide a magnetic bias field on the free layer to achieve deterministic switching. The antiferromagnetic layer is positioned below the ferromagnetic bias layer and is configured to pin a magnetization direction of the ferromagnetic bias layer in a predetermined direction.
1. A method for deterministically switching a free layer, having two bi-stable magnetization directions, in a spin orbit torque magnetoresistive random access memory (SOT-MRAM) cell, comprising:
providing a current through a ferromagnetic bias layer with tapered edges such that a magnetization direction of the ferromagnetic bias layer to provide a spin orbit torque via anomalous Hall effect creates an angle with respect to a direction of the current to generate a magnetic bias field parallel with the direction of the current as well as a spin current perpendicular to the cell to deterministically switch the free layer from a first magnetization state to a second magnetization state, wherein an antiferromagnetic layer is positioned adjacent to the ferromagnetic bias layer and is configured to pin a magnetization direction of the ferromagnetic bias layer in a predetermined direction.
2. The method of claim 1 , wherein the angle created between the direction of the magnetization of the ferromagnetic bias layer and the direction of the current is about 45 degrees.
3. The method of claim 2 , wherein the current provided to the ferromagnetic bias layer is a write current.
4. The method of claim 3 , wherein the ferromagnetic bias layer may be shaped to adjust a strength of a stray magnetic field generated by the ferromagnetic bias layer.
5. The method of claim 4 , wherein the ferromagnetic bias layer comprises:
a spin Hall effect layer; and
a ferromagnetic bias layer configured to provide a magnetic bias field.
6. The method of claim 5 , wherein the current may be selectively provided to the spin-Hall effect layer to continue to deterministically switch the free layer between magnetization states.
7. The method of claim 1 , wherein the current provided to the ferromagnetic bias layer is a write current.
8. The method of claim 7 , wherein the ferromagnetic bias layer may be shaped to adjust a strength of a stray magnetic field generated by the ferromagnetic bias layer.
9. The method of claim 8 , wherein the ferromagnetic bias layer comprises:
a spin Hall effect layer; and
a ferromagnetic bias layer configured to provide a magnetic bias field.
10. The method of claim 9 , wherein the current may be selectively provided to the spin-Hall effect layer to continue to deterministically switch the free layer between magnetization states.
11. The method of claim 1 , wherein the ferromagnetic bias layer may be shaped to adjust a strength of a stray magnetic field generated by the ferromagnetic bias layer.
12. The method of claim 11 , wherein the ferromagnetic bias layer comprises:
a spin Hall effect layer; and
a ferromagnetic bias layer configured to provide a magnetic bias field.
13. The method of claim 12 , wherein the current may be selectively provided to the spin-Hall effect layer to continue to deterministically switch the free layer between magnetization states.
14. The method of claim 1 , wherein the ferromagnetic bias layer comprises:
a spin Hall effect layer; and
a ferromagnetic bias layer configured to provide a magnetic bias field.
15. The method of claim 14 , wherein the current may be selectively provided to the spin-Hall effect layer to continue to deterministically switch the free layer between magnetization states.
16. The method of claim 1 , wherein the current may be selectively provided to the spin-Hall effect layer to continue to deterministically switch the free layer between magnetization states.