Mechanism of paramagnetic spin Seebeck effect

We have theoretically investigated the spin Seebeck effect (SSE) in a normal metal (NM)/paramagnetic insulator (PI) bilayer system. Through linear response approach, we calculated thermal pumping from PI to NM and backflow current PI, where spin-flip scattering via interfacial exchange coupling between conduction-electron localized is taken into account. found finite appears at interface under difference effective temperatures spins its intensity increases by increasing density of $S$. Our model well reproduces magnetic-field-induced reduction paramagnetic SSE Pt/${\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ experimentally observed when Zeeman energy comparable energy, which can be interpreted as suppression scattering. The present finding provides an insight mechanism SSEs thermally induced spin-current generation magnetic materials.