Mn-induced ferromagnetism and enhanced thermoelectric properties in Ru1−x Mn x Sb2+δ

We report the experimental investigation of Mn doping effect on the electrical, magnetic, and thermal properties of Ru1-xMnxSb2+delta single crystals. While RuSb2+delta is a diamagnetic semiconductor, partial replacement of Ru by Mn results in ferromagnetism with the Curie temperature 536 K and 540 K for x = 0.04 and 0.08, respectively. Correspondingly, the electrical resistivity decreases dramatically and shows metallic character due to the increased electron concentration. Surprisingly, the magnitude of the thermopower increases upon Mn doping, reaching -250 mu V K-1 at 300 K for x = 0.08, while the thermal conductivity remains unchanged above 100 K. These indicate a strong modification of electronic structure by doped Mn, leading to enhanced thermoelectric properties. The carriers induced by Mn not only decrease the resistivity, but also mediate the long-range ferromagnetic ordering in Ru1-xMnxSb2+delta.