Probing polarization-tunable sub-terahertz spin pumping in bimodal α-Fe₂O₃/Pt

Hematite (α-Fe₂O₃) is an insulating antiferromagnet possessing a room temperature canted phase induced by the super-exchange Dzyaloshinskii-Moriya Interaction (DMI), resulting in enhanced spin pumping and spin transport over uniaxial antiferromagnets. In this work we resonantly excite the quasi-ferromagnetic (acoustic) and purely antiferromagnetic (optical) spin-dynamical modes in bulk and thin-film heterostructures of α-Fe₂O₃/Pt at room temperature, inducing inverse-spin-Hall-voltages up to 255 GHz. Following recent measurements of optical-mode spin-pumping in α-Fe₂O₃, we observe a novel and exotic microwave polarization mapping along with amplified spin-charge conversion in the optical branch and discuss the implications of layer thickness on acoustic and optical spin-modes. The results provide a deeper understanding of spin-wave selection rules for canted antiferromagnets and their potential use in nanoscale terahertz spintronics.. Authors: Fritjofson, Gregory [Univ. of Central Florida, Orlando, FL (United States)]; Regmi, Atul [Univ. of Central Florida, Orlando, FL (United States)]; Hanson-Flores, Jacob [Univ. of Central Florida, Orlando, FL (United States)]; Michel, Justin [The Ohio State Univ., Columbus, OH (United States)]; Tang, Junyu [The Ohio State Univ., Columbus, OH (United States); Univ. of California, Riverside, CA (United States)]. DOE Contract: SC0001304. Subjects: interfaces; magnetic materials; magnetic properties; spintronics; surfaces; thin films