Entropy changes due to the first-order phase transition in the Gd5SixGe4-x system

Entropy changes due to magnetostructrual phase transition in Gd5SixGe4-x intermetallics have been studied based on a systematic analysis of experiment data and mean-field theory calculations. It is found that the magnetic and lattice entropy changes have the same sign. Further analysis indicates that the main entropy change (similar to 60%-similar to 80%) comes from the field-induced change of the magnetic order, while the rest arise from the entropy difference of the two crystallographic modifications joined by the structural transition, probably due to the variation of the lattice vibration mode. The present work reveals the importance of lattice entropy for a system experiencing a first-order transition. (c) 2006 American Institute of Physics.