Origin of transverse voltages generated by thermal gradients and electric fields in ferrimagnetic-insulator/heavy-metal bilayers

We compare thermal-gradient-driven transverse voltages in ferrimagnetic-insulator/heavy-metal bilayers (${\mathrm{Tm}}₃{\mathrm{Fe}}₅{\mathrm{O}}₁₂/\mathrm{W}$ and ${\mathrm{Tm}}₃{\mathrm{Fe}}₅{\mathrm{O}}₁₂/\mathrm{Pt}$) to corresponding electrically driven transverse resistances at and above room temperature. We find for ${\mathrm{Tm}}₃{\mathrm{Fe}}₅{\mathrm{O}}₁₂/\mathrm{W}$ that the thermal and electrical effects can be explained by a common spin-current detection mechanism, the physics underlying spin Hall magnetoresistance (SMR). However, for ${\mathrm{Tm}}₃{\mathrm{Fe}}₅{\mathrm{O}}₁₂/\mathrm{Pt}$ the ratio of the electrically driven transverse voltages (planar Hall signal/anomalous Hall signal) is much larger than the ratio of corresponding thermal-gradient signals, a result which is very different from expectations for a SMR-based mechanism alone. We ascribe this difference to a proximity-induced magnetic layer at the ${\mathrm{Tm}}₃{\mathrm{Fe}}₅{\mathrm{O}}₁₂/\mathrm{Pt}$ interface.