Spin Fluctuation: A new route for enhancing zT in thermoelectrics

Spin fluctuations (SF) have already shown improving thermopower, but enhancing thermoelectric figure-of-merit (zT) has not been reported until now. We evidence remarkable zT enhancement (~80%) from SF in the ferromagnetic CrTe near and below the Curie temperature, T_C~335 K. The ferromagnetism in CrTe originates from the collective electronic and localized magnetic moments. The temperature- and field-dependent transport properties demonstrate the profound impact of SF on the electrons and phonons. The suppression of the SF with an external magnetic field leads to a strong reduction of the thermopower and enhancement of the thermal conductivity near and below T_C. The anomalous transport properties are investigated and analyzed based on theoretical models, and a good agreement with experimental data is found. Moreover, the detailed analysis of transport properties proves that spin-wave has an insignificant contribution to the transport properties. This study is contributory to understanding the SF-mediated thermoelectric properties and designing high-performance spin-driven thermoelectric materials.