Generic Seebeck effect from spin entropy

Abstract

How magnetism affects the Seebeck effect is an important issue of wide concern in the thermoelectric community but remains elusive. Based on a thermodynamic analysis of spin degrees of freedom on varied d-electron-based ferromagnets and antiferromagnets, we demonstrate that in itinerant or partially itinerant magnetic compounds there exists a generic spin contribution to the Seebeck effect over an extended temperature range from slightly below to well above the magnetic transition temperature. This contribution is interpreted as resulting from transport spin entropy of (partially) delocalized conducting d electrons with strong thermal spin fluctuations, even semiquantitatively in a single-band case, in addition to the conventional diffusion part arising from their kinetic degrees of freedom. As a highly generic effect, the spin-dependent Seebeck effect might pave a feasible way toward efficient “magnetic thermoelectrics.” Public summary: • Magnetism can offer a significant contribution to thermoelectricity • A generic Seebeck effect exists in magnetic conductors as a result of transport spin entropy of delocalized d electrons • The magnetocaloric effect and the Seebeck effect are thermodynamically correlated with each other

Keywords

• Seebeck effect
• magnetocaloric effect
• spin entropy
• thermoelectric material