High efficiency spin torque switching using a ferrimagnet
AssigneeNational University of Singapore
InventorsHyunsoo Yang, Rahul Mishra, Jiawei Yu
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Abstract
In one embodiment, a spin torque device uses a thick (e.g., >1 nm, and preferably >=2-6 nm) ferrimagnet (FIM) layer, instead of a thin (e.g., <1-2 nm) FM layer in the device's stack. The FIM layer may be composed of a cobalt-gadolinium (Co—Gd) alloy, cobalt-terbium (Co—Tb) multilayers, or other materials that provide anti-ferromagnetic coupling between two sub-lattices. Negative exchange interaction between the two sub-lattices of the FIM may allow for low current switching. High thermal stability and external magnetic field resistance may also be achieved.
Claims19
A spin-orbit torque (SOT) device arranged as a stack, comprising:
- a substrate;
- a heavy metal (HM) layer;
- a ferrimagnet (FIM) layer disposed adjacent to the heavy metal layer, the FIM layer constructed from a material that provides anti-ferromagnetic coupling between two sub-lattices, the FIM layer having a thickness greater than 1 nanometer (nm);
- and
- a capping layer,
- wherein the stack of the SOT device is arranged such that, when an in-plane current is applied to the HM layer of the SOT device, a spin from the HM layer diffuses into the FIM layer to produce negative exchange interaction between the two sub-lattices of the FIM layer, which provides additional torque that assists current induced SOT magnetization switching of the SOT device.
A spin-orbit torque (SOT) device arranged as a stack, comprising:
- a substrate;
- a heavy metal (HM) layer;
- a ferrimagnet (FIM) layer disposed adjacent to the heavy metal layer, the FIM layer constructed from a material that provides anti-ferromagnetic coupling between two sub-lattices, the FIM layer having a thickness greater than 1 nanometer (nm);
- and
- a capping layer,
- wherein the stack of the SOT device is arranged such that negative exchange interaction between the two sub-lattices of the FIM layer provides additional torque that assists current induced SOT magnetization switching of the SOT device.
A method for switching a spin-orbit torque (SOT) device that is arranged as a stack that includes a substrate, a heavy metal (HM) layer, a ferrimagnet (FIM) layer, and a capping layer, the method comprising:
- applying an in-plane current to the HM layer;
- in response to the applied current, producing an anti-damping torque in the FIM layer that tilts two magnetic sub-lattices of the FIM causing an exchange field;
- producing a negative exchange interaction torque that acts in opposite directions on the two magnetic sub-lattices,
- wherein the negative exchange interaction torque assists magnetization switching of the SOT device when the in-plane current is applied.
Dependencies are inferred from the claim text.