  The spin Seebeck effect (SSE) refers to the generation of a spin current as a
result of a temperature gradient in magnetic materials including insulators.
The SSE is applicable to thermoelectric generation because the thermally
generated spin current can be converted into a charge current via spin-orbit
interaction in conductive materials adjacent to the magnets. The
insulator-based SSE device exhibits unconventional characteristics potentially
useful for thermoelectric applications, such as simple structure, device-design
flexibility, and convenient scaling capability. In this article, we review
recent studies on the SSE from the viewpoint of thermoelectric applications.
Firstly, we introduce the thermoelectric generation process and measurement
configuration of the SSE, followed by showing fundamental characteristics of
the SSE device. Secondly, a theory of the thermoelectric conversion efficiency
of the SSE device is presented, which clarifies the difference between the SSE
and conventional thermoelectric effects and the efficiency limit of the SSE
device. Finally, we show preliminary demonstrations of the SSE in various
device structures for future thermoelectric applications and discuss prospects
of the SSE-based thermoelectric technologies.
