Interfacial Origin of Unconventional Spin‐Orbit Torque in Py/γ−$\gamma -$IrMn3

Abstract

AbstractAngle‐resolved spin‐torque ferromagnetic resonance measurements are carried out in heterostructures consisting of Py (Ni81Fe19) and a noncollinear antiferromagnetic quantum material IrMn3. The structural characterization reveals that IrMn3 is polycrystalline in nature. A large exchange bias of 158 Oe is found in Py/IrMn3 at room temperature, while IrMn3/Py and Py/Cu/IrMn3 exhibit no exchange bias. Regardless of the exchange bias and stacking sequence, a substantial unconventional out‐of‐plane anti‐damping torque is observed when IrMn3 is in direct contact with Py. The magnitude of the out‐of‐plane spin‐orbit torque efficiency is found to be twice as large as the in‐plane spin‐orbit torque efficiency. The unconventional spin‐orbit torque vanishes when a Cu spacer is introduced between Py and IrMn3, indicating that the unconventional spin‐orbit torque in this system originates at the interface. These findings are important for realizing efficient antiferromagnet‐based spintronic devices via interfacial engineering.