Enhanced thermopower via spin-state modification

TL;DR

This study demonstrates that applying pressure modifies the spin state of cobalt ions in Sr$_{3.1}$Y$_{0.9}$Co$_{4}$O$_{10+ ext{delta}}$, leading to enhanced thermopower, highlighting the role of spin-state control in thermoelectric materials.

Contribution

It reveals how pressure-induced spin-state changes in cobalt oxides can significantly improve thermoelectric performance, a novel approach in the field.

Findings

Pressure reduces magnetization via spin-state change.

Seebeck coefficient increases with pressure, especially at low temperatures.

Spin-orbital entropy influences thermoelectric properties.

Abstract

We investigated the effect of pressure on the magnetic and thermoelectric properties of Sr$_{3.1}$Y$_{0.9}$Co$_{4}$O$_{10+\delta }$. The magnetization is reduced with the application of pressure, reflecting the spin-state modification of the Co$^{3+}$ ions into the nonmagnetic low-spin state. Accordingly, with increasing pressure, the Seebeck coefficient is enhanced, especially at low temperatures, at which the effect of pressure on the spin state becomes significant. These results indicate that the spin-orbital entropy is a key valuable for the thermoelectric properties of the strongly correlated cobalt oxides.