Entropy change and magnetocaloric effect in Gd5(SixGe1-x)4

Isothermal magnetization curves up to 23 T have been measured in Gd5Si1.8Ge2.2. We show that the values of the entropy change at the first-order magnetostructural transition, obtained from the Clausius-Clapeyron equation and the Maxwell relation, are coincident, provided the Maxwell relation is evaluated only within the transition region and the maximum applied field is high enough to complete the transition. These values are also in agreement with the entropy change obtained from differential scanning calorimetry. We also show that a simple phenomenological model based on the temperature and field dependence of the magnetization accounts for these results

Scaling of the entropy change at the magnetoelastic transition in Gd5(SixGe1-x)4

Differential scanning calorimetry under a magnetic field H has been used to measure the entropy change DS at the magnetoelastic transition in Gd5(SixGe12x)4 alloys, for x<0.5. We show that DS scales with the transition temperature, Tt , which is tuned by x and H, from 70 to 310 K. Such a scaling demonstrates that Tt is the relevant parameter in determining the giant magnetocaloric effect in these alloys, and proves that the magnetovolume effects due to H are of the same nature as the volume effects caused by substitutio