Spin pumping in a material with metal-insulator transition

Ferromagnetic resonance driven spin pumping is a powerful tool to study the generation and detection of pure spin currents. Using spin pumping, people have characterized the spin orbit interaction induced charge—spin conversion in various materials, including paramagnetic, ferromagnetic and antiferromagnetic metals, semiconductors, as well as superconductors. It is interesting to ask whether the charge to spin conversion efficiency undergoes any significant change in a material with spontaneous phase transitions. In this talk we will present our work on spin pumping in VO₂, a prototype metal-insulator transition (MIT) material. By exciting ferromagnetic resonance in an adjacent magnetic insulator, we are able to inject spin current into VO₂ and quantify the variation in spin pumping voltage during the phase transition. We find that large spin pumping voltages exist in both metallic and insulating phase of VO₂, despite of the huge resistance change across this transition. To this end, we will present our work on the variation of spin mixing conductance and the spin Hall angle across the phase transition region.