Asymmetry of the latent heat signature in b-axis oriented single crystal Gd Si Ge

A 100 micron fragment of a b-axis oriented single crystal Gd Si Ge has been studied using microcalorimetry, enabling the separate measurement of the heat capacity and the latent heat. The sample was taken from the same crystal previously studied with Hall probe imaging, which showed that the phase transition is seeded by a second phase of Gd Si Ge nanoplatelets on the increasing field sweep direction only. The multiple transition features observed in the latent heat signature suggests a nucleation size of approximately 20 μm, consistent with the lengthscale suggested by Hall imaging. The difference in nucleation and growth process with field sweep direction is clearly identified in the latent heat. We show that the latent heat contribution to the entropy change is of the order of 50% of the total entropy change and unlike other systems studied, the transition does not broaden (and the latent heat contribution does not diminish significantly) as magnetic field and temperature are increased within the parameter range explored in these experiments.