Theory of spin transport induced by the temperature gradient

TL;DR

This paper develops a microscopic theory showing that temperature gradients can generate spin currents and relaxation torques in ferromagnetic metals, with effects proportional to the gradient and its second derivative.

Contribution

It introduces a microscopic framework describing how temperature gradients induce spin transport phenomena, highlighting their equivalence to electric field effects.

Findings

Temperature gradient acts as an effective field for spin current generation.

Spin current contribution is proportional to the temperature gradient.

Relaxation torque is proportional to the second derivative of temperature.

Abstract

Spin transport driven by the temperature gradient in ferromagnetic metals is studied based on a microscopic theory. It is shown that the temperature gradient works as an effective field equivalent to the electric field as for both the spin current generation and the spin relaxation torque. The thermally driven contribution of the spin current and the relaxation torque are thus proportional to $\nabla T$ and $\nabla^2 T$, respectively.