Structural, magnetic and magnetocaloric properties of double perovskites Ba2-xLaxFeMoO6

We report the possible variations in the structural and magnetocaloric properties induced by the controlled La-substitution at the Ba-site in Ba2-xLaxFeMoO6 (0.0 <= x <= 0.4) samples. The samples were prepared using the conventional solid state reaction method. The X-ray diffraction patterns confirmed the formation of cubic crystal structure (Fm-3m) in all the samples. The magnetization vs. temperature curves showed a single transition from ferromagnetic to paramagnetic phase with increasing temperature. In the low doped samples (up to x = 0.2) the increase in the Curie temperature is attributed to the electronic effects whereas the almost similar T-C values recorded in the higher La-doped samples (x = 0.3 and 0.4) is due to the competition between the band filling effect and the steric effect. The Arrott plots confirmed a second order of magnetic phase transition in each sample. The pure Ba2FeMoO6 sample showed the highest magnetic entropy change value of 0.93 Jkg(-1)K(-1) at a low applied field of 2.5 T, the largest relative cooling power (72 Jkg(-1)) however is observed for the Ba1.9La0.1FeMoO6 sample which is attributed to the broad magnetic entropy curve obtained for this composition. The results obtained here clearly reveal that the Curie temperature and magnetocaloric properties of the host Ba2FeMoO6 material can be effectively modified by La-doping that makes this compound a promising base material for establishing novel magnetic refrigerants.