Entropy changes associated with the first-order magnetic transition in LaFe13−xSix

Entropy changes accompanying a first-order magnetic transition have been studied for the intermetallic alloys LaFe13−xSix. An expression of the entropy change due to lattice expansion/contraction is derived based on the general thermodynamics theory. Combining it with the structural/magnetic measurements, and the mean-field-theory analyses, changes in magnetic, lattice, and electronic entropies are estimated. It is found that although magnetic entropy change is dominant, lattice entropy change is comparably large and cancels out most of the magnetic one. In contrast, electronic entropy change is negligibly small.