Spin Current Physics and Its Thermoelectric Application

Abstract

Spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in magnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin–orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This “longitudinal spin Seebeck effect” in insulators provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin Hall effects.