Interfacial Origin of Unconventional Spin‐Orbit Torque in Py/γ−$\gamma -$IrMn <sub>3</sub>
Akash Kumar, Pankhuri Gupta, Niru Chowdhury, Kacho Imtiyaz Ali Khan, Utkarsh Shashank, Surbhi Gupta, Yasuhiro Fukuma, Sujeet Chaudhary, P. K. Muduli
Abstract
Abstract Angle‐resolved spin‐torque ferromagnetic resonance measurements are carried out in heterostructures consisting of Py (Ni 81 Fe 19 ) and a noncollinear antiferromagnetic quantum material IrMn 3 . The structural characterization reveals that IrMn 3 is polycrystalline in nature. A large exchange bias of 158 Oe is found in Py/IrMn 3 at room temperature, while IrMn 3 /Py and Py/Cu/IrMn 3 exhibit no exchange bias. Regardless of the exchange bias and stacking sequence, a substantial unconventional out‐of‐plane anti‐damping torque is observed when IrMn 3 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 IrMn 3 , 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.