Probing Polarization-Tunable Sub-Terahertz Spin Pumping in Bimodal α-Fe2O3 /Pt

Hematite (α-Fe ₂ O ₃ ) 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-Fe ₂ O ₃ /Pt at room temperature, inducing inverse-spin-Hall-voltages up to 255GHz. Following recent measurements of optical-mode spin-pumping in α-Fe ₂ O ₃ , we observe a novel and exotic microwave polarization mapping along with amplified spin-charge conversion of optical spin-charge conversions 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.