  The spin Seebeck effect (SSE) refers to the generation of a spin current as a
result of a temperature gradient in a magnetic material, which can be detected
electrically via the inverse spin Hall effect in a metallic contact. Since the
discovery of SSE in 2008, intensive studies on SSE have been conducted to
elucidate its origin. SSEs appear in a wide range of magnetic materials
including ferro-, ferri-, and antiferro-magnets and also paramagnets with
classical or quantum spin fluctuation. SSE voltage reflects fundamental
properties of a magnet, such as elementary excitation, static magnetic order,
spin correlation, and spin transport. In this article, we review recent
progress on SSEs in various systems, with particular emphasis on its emerging
role as a probe of these magnetic properties in solids. We also briefly discuss
the recently-discovered nuclear SSE.
