CrTe as a versatile thermoelectromagnetic multi-functional material

Materials with large magnetocaloric effects and high thermoelectric performance are of fundamental interest to all-solid-state refrigeration technology. Herein, we report CrTe-based ferromagnetic semi-metals as an exceptional example showing both desirable magnetic entropy change (-& UDelta;S-M) and promising thermoelectric figure of merit (ZT) near room temperature. A proper amount (9 mol. %) of Cr deficiency is found to stabilize the hexagonal structure of CrTe. Cr0.91Te displays a maximum -& UDelta;S-M value of & SIM;2.4 J/Kg & BULL;K under an applied magnetic field of 5 T around its Curie temperature (T-C) of 332 K and a strikingly large ZT value of 1.2 x 10(-2) at 300 K (two to four orders of magnitude larger than any other ferromagnetic compounds reported so far). The exceptional thermoelectric performance in such a semi-metal is believed to originate from the inherently strong electron-phonon-spin interactions: magnon-drag effect mediated Seebeck coefficient enhancement and phonon-spin coupling induced thermal conductivity reduction. The introduction of antiferromagnetic CrSb not only systematically decreases T-C of Cr0.91Te down to or even below room temperature but also boosts its thermoelectromagnetic properties. Specifically, Cr0.91Te0.9Sb0.1 obtains a maximum -& UDelta;S-M value of & SIM;2.6 J/Kg & BULL;K @ 5 T around T-C = 315 K and a ZT value of 2.0 x 10(-2) at 300 K, which represent 8% and 75% improvement over pristine Cr0.91Te, respectively. This research highlights the possibility of exploring ferromagnetic semi-metals as advanced thermoelectromagnetic multi-functional materials.