Spontaneous generation of voltage in Gd5(SixGe4−x) during a first-order phase transition induced by temperature or magnetic field

Abstract

The spontaneous generation of voltage has been observed during the first-order magnetic-Martensitic phase transition process in ${\mathrm{Gd}}_5{(\mathrm{S}\mathrm{i}}_x{\mathrm{Ge}}_{4-x})$ alloys regardless of whether the transformation is triggered by temperature or magnetic field. Based on various experimental data we show that thermoelectric power is a major contributor to the observed voltage. The characteristics of the simultaneously recorded spontaneous voltage and the signal from a differential thermocouple attached to the sample are quite complex, indicating that thermal effects arising in this class of materials during the first-order phase transition are nontrivial. The unusual dynamics of both the heat release and absorption during the phase transformations in ${\mathrm{Gd}}_5{(\mathrm{S}\mathrm{i}}_x{\mathrm{Ge}}_{4-x})$ result in the appearance of temperature gradients and, therefore, thermoelectricity.