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arXiv · 1804.07776

Polaronic transport and thermoelectricity in Fe$_{1-x}$Co$_x$Sb$_2$S$_4$ ($x$ = 0, 0.1, and 0.2)

Yu Liu·Chang-Jong Kang·Eli Stavitski·Qianheng Du·Klaus Attenkofer·G. Kotliar·C. Petrovic
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Abstract

We report a study of Co-doped berthierite Fe$_{1-x}$Co$_x$Sb$_2$S$_4$ ($x$ = 0, 0.1, and 0.2). The alloy series of Fe$_{1-x}$Co$_x$Sb$_2$S$_4$ crystallize in an orthorhombic structure with the Pnma space group, similar to FeSb$_2$, and show semiconducting behavior. The large discrepancy between activation energy for conductivity, $E_ρ$ (146 $\sim$ 270 meV), and thermopower, $E_S$ (47 $\sim$ 108 meV), indicates the polaronic transport mechanism. Bulk magnetization and heat capacity measurements of pure FeSb$_2$S$_4$ ($x$ = 0) exhibit a broad antiferromagnetic (AFM) transition ($T_N$ = 46 K) followed by an additional weak transition ($T^*$ = 50 K). Transition temperatures ($T_N$ and $T^*$) slightly decrease with increasing Co content $x$. This is also reflected in the thermal conductivity measurement, indicating strong spin-lattice coupling. Fe$_{1-x}$Co$_x$Sb$_2$S$_4$ shows relatively high value of thermopower (up to $\sim$ 624 $μ$V K$^{-1}$ at 300 K) and thermal conductivity much lower when compared to FeSb$_{2}$, a feature desired for potential applications based on FeSb$_{2}$ materials.

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Yu Liu, Chang-Jong Kang, Eli Stavitski, Qianheng Du, Klaus Attenkofer, G. Kotliar, C. Petrovic. 2018-04-20. Polaronic transport and thermoelectricity in Fe$_{1-x}$Co$_x$Sb$_2$S$_4$ ($x$ = 0, 0.1, and 0.2). https://doi.org/10.1103/physrevb.97.155202

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