Polaronic transport and thermoelectricity in Mn3Si2Te6 single crystals
Abstract
We carried out a comprehensive study of the structural, electrical transport, thermal and thermodynamic properties in ferrimagnetic Mn3Si2Te6 single crystals. Mn and Te K-edge X-ray absorption spectroscopy and synchrotron powder X-ray diffraction were measured to provide information on the local atomic environment and the average crystal structure. The dc and ac magnetic susceptibility measurements indicate a second-order paramagnetic to ferrimagnetic transition at Tc 74 K, which is further confirmed by the specific heat measurement. Mn3Si2Te6 exhibits semiconducting behavior along with a large negative magnetoresistance of -87\% at Tc and relatively high value of thermopower up to 10 mV/K at 5 K. Besides the rapidly increasing resistivity (T) and thermopower S(T) below 20 K, the large discrepancy between activation energy for resistivity E and thermopower ES above 20 K indicates the polaronic transport mechanism. Furthermore, the thermal conductivity (T) of Mn3Si2Te6 is notably rather low, comparable to Cr2Si2Te6, and is strongly suppressed in magnetic field across Tc, indicating the presence of strong spin-lattice coupling, also similar with Cr2Si2Te6.
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