Low temperature spin Seebeck effect in non-magnetic VO₂ thin film

The spin Seebeck effect (SSE) involves the generation of spin current in the presence of a heat flow across a magnetically active material. SSE in paramagnets is considerably less studied, and the mechanism of paramagnetic SSE is still unclear. Here we present a systematic study of the longitudinal SSE (LSSE) in insulating VO₂ film at low temperatures. The LSSE grows linearly with increasing field at low fields but experiences a field-induced reduction at high fields and the lowest temperatures, qualitatively consistent with the recent model of paramagnetic SSE response. The LSSE shows the expected angular dependence with the in-plane field orientation and is linear in the heating power. The sign of the LSSE response is not consistent with that expected for a triplon-dominated SSE. Finally, we will show how thickness of VO₂ film influences the temperature dependence of LSSE magnitude.