Spin Seebeck effect at low temperatures in the nominally paramagnetic insulating state of vanadium dioxide

TL;DR

This study reports a nonlocal spin Seebeck effect in vanadium dioxide films at low temperatures, revealing unexpected paramagnetic spin responses in a phase typically considered nonmagnetic.

Contribution

It demonstrates the existence of a paramagnetic spin Seebeck effect in VO2's insulating phase, challenging the conventional understanding of its magnetic properties.

Findings

Spin Seebeck signal appears below 30 K

Signal increases with decreasing temperature

Response is non-hysteretic with magnetic field

Abstract

The low temperature monoclinic, insulating phase of vanadium dioxide is ordinarily considered nonmagnetic, with dimerized vanadium atoms forming spin singlets, though paramagnetic response is seen at low temperatures. We find a nonlocal spin Seebeck signal in VO2 films that appears below 30 K and which increases with decreasing temperature. The spin Seebeck response has a non-hysteretic dependence on in-plane external magnetic field. This paramagnetic spin Seebeck response is discussed in terms of prior findings on paramagnetic spin Seebeck effects and expected magnetic excitations of the monoclinic ground state.