Magnetic memory and a method of operating magnetic memory
In example embodiments, a SOT magnetic memory and operation method are provided that utilize SOT driven domain wall motion to achieve subsequent switching without the need for an external assist magnetic field. The magnetic memory includes a magnetic tunnel junction having a reference layer, a tunnel barrier layer and a free layer, where the tunnel barrier layer is positioned between the reference layer and free layer. A spin-orbit torque layer is disposed adjacent to the free layer. A pair of pinning site are positioned at a longitudinal end of the free layer and each has an opposite magnetization direction from the other. The SOT layer is configured to exert SOT and switch a magnetization direction of the free layer via domain wall motion in a direction of current flow when an electric current is passed through a length of the SOT layer.
1. A magnetic memory comprising:
a magnetic tunnel junction (MTJ) that includes a reference layer, a tunnel barrier layer and a free layer, the tunnel barrier layer positioned between the reference layer and free layer;
a spin-orbit torque (SOT) layer disposed adjacent to the free layer; and
a pair of pinning sites, each pinning site positioned at a longitudinal end of the free layer and having an opposite magnetization direction from each other,
wherein the SOT layer is configured to exert SOT and switch a magnetization direction of the free layer via domain wall motion in a direction of current flow when an electric current is passed through a length of the SOT layer.
2. The magnetic memory of claim 1 , wherein the free layer includes tapered regions at the longitudinal ends meeting the pinning sites, wherein the tapered regions have at least one of a tapered width or a tapered thickness such that the pair of pinning sites are at least one of wider or thicker than a portion of the free layer.
3. The magnetic memory of claim 2 , wherein the tapered regions have a tapered width such that the pair of pinning sites are wider than the portion of the free layer.
4. The magnetic memory of claim 3 , wherein the SOT layer is also tapered at its longitudinal ends such that the longitudinal ends of the SOT layers are wider than the portion of the free layer.
5. The magnetic memory of claim 2 , wherein the tapered regions have a tapered thickness such that the pair of pinning sites are thicker than the portion of the free layer.
6. The magnetic memory of claim 2 , wherein the tapered regions have both a tapered thickness and a tapered width such that the pair of pinning sites are both wider and thicker than the portion of the free layer.
7. The magnetic memory of claim 1 , wherein the SOT layer is configured to switch the magnetization direction of the free layer in the absence of an assist magnetic field.
8. The magnetic memory of claim 1 , wherein the pinning sites are configured to provide non-homogenous magnetic anisotropy with respect to the free layer.
9. The magnetic memory of claim 1 , wherein at least one of the SOT layer or the free layer is configured to provide non-uniform current density throughout a length thereof.
10. The magnetic memory of claim 1 , wherein the magnetized state of the free layer is based on the direction of current flow and on magnetization direction of the pinning sites.
11. The magnetic memory of claim 1 , further comprising a device protection layer disposed over the reference layer.
12. The magnetic memory of claim 1 , further comprising a first terminal electrically connected to the reference layer, a second terminal electrically connected to the pinning site at one longitudinal end of the SOT layer, and a third terminal electrically connected to the pinning site that the other longitudinal end of the SOT layer.
13. The magnetic memory of clause 12 , wherein passing electric current through the second and third terminals allows the electric current to be passed through the length of the SOT layer.
14. The magnetic memory of claim 1 , wherein the reference layer is biased at a reference magnetic state.