Large thermopower in the antiferromagnetic semiconductor BaMn$_2$Bi$_2$

TL;DR

This study investigates the electrical and thermal transport properties of the antiferromagnetic semiconductor BaMn$_2$Bi$_2$, revealing a significant thermopower peak near 80 K and its enhancement under magnetic fields, indicating potential thermoelectric applications.

Contribution

The paper reports the discovery of large thermopower in BaMn$_2$Bi$_2$ and details its temperature-dependent transport behavior, highlighting the impact of magnetic fields on thermopower.

Findings

Thermopower peaks at ~150 μV/K near 80 K

Magnetic field increases thermopower to 210 μV/K

Carrier density changes abruptly at the metal-semiconductor transition

Abstract

We report electrical and thermal transport properties of Mn-based material BaMn$_2$Bi$_2$ with ThCr$_2$Si$_2$ structure. The resistivity of the antiferromagnetic BaMn$_2$Bi$_2$ shows a metal-semiconductor transition at $\sim 80$ K with decreasing temperature. Correspondingly, the thermopower $S$ shows a peak at the same temperature, approaching ~150 $\mu$V/K. With increasing temperature $S$ decreases to about 125 $\mu$V/K at the room temperature. The magnetic field enhances the peak value to 210 $\mu$V/K. The Hall resistivity reveals an abrupt change of the carrier density close to the metal-semiconductor transition temperature.