Role of lattice contraction in the magnetocaloric effect

The magnetocaloric effect (MCE) and metamagnetic transition of LaFe11.5Si1.5 compound are studied by the measurement of magnetization, ac susceptibility, and heat capacity. The ferromagnetic order temperature is observed to be 196 K. The field-induced metamagnetic transition that causes a paramagneticto-ferromagnetic transition takes place above 196 K. Although it is fairly strong, the MCE in LaFe11.5Si1.5 is much weaker than expected in theory. Possible mechanisms are discussed based on the thermodynamics theory. It is possible that the magnetic entropy change is counteracted by the lattice entropy change resulting from the lattice contraction of the compound at the magnetic transition. (Some figures in this article are in colour only in the electronic version)