Enhanced Thermopower In The Antiferromagnetic Phase Of Mn2-Xcxsb

Thermoelectric properties of chromium-modified Mn2Sb are systematically investigated to evaluate the power factors. Single-crystalline samples of Mn2-xCxSb with 0 <= x <= 0.1 were successfully grown by a slow cooling method. As temperature decreases, the resistivities of Cr-doped samples decrease and exhibit a clear jump with hysteresis, reflecting a first-order transition from a ferrimagnetic (F1) to an antiferromagnetic (AF) phase. At this transition, the Seebeck coefficient changes its sign from positive to negative, and its magnitude is notably enhanced. In the AF phase, the magnitude of the Seebeck coefficient reaches 28 mu V/K at a maximum. The largest power factor is observed for the sample of x = 0.04, and 4.86 mu W/cm K-2 at 50K. This power factor is about fifty times as large as that of x = 0 in the FI phase. Based on a band-structure calculation and a photoemission spectroscopy measurement, we attribute the enhanced thermoelectric property in the AF phase to a sharp peak in the density of state around the Fermi level.