Magnetocaloric effect in La_(1-x)Sr_(x)MnO_(3) for x=0.13 and 0.16

摘要

Magnetization of polycrystalline La_(1-x)Sr_(x)MnO_(3) samples with x=0.13 and x=0.16 has been measured as a function of temperature and external magnetic field. Using the gathered data and the thermodynamic Maxwell's relation, changes of the magnetic contribution to entropy under influence of the magnetic field, allowing to estimate the value of magnetocaloric effect, have been determined. The changes reach ～7 J/(kg K) in the field of 7 T, which makes the studied samples good candidates for application for magnetic refrigeration. Expressions describing entropy and its change under influence of magnetic field have been derived in the molecular field approximation. Satisfactory agreement between the theoretical curves and the experimental dependencies has been found.