Lanthanum Concentration Effect of Magnetocaloric Properties in LaxMnO3-δ

Magnetocaloric properties of LaxMnO3-delta films in the composition range 0.75 <= x <= 1 near phase transition from a ferromagnetic to a paramagnetic state were investigated. For x > 0.75 composition, it is showed that the increasing of La concentration improves magnetocaloric properties. It is also showed that post-annealing films in O-2 improves magnetocaloric effect. The magnetocaloric properties are affected by Mn+3/Mn+4 ratios, which can be varied either by changing La concentration or varying the oxygen content in the LaxMnO3-delta system. Moreover, LaxMnO3-delta films can be used as a working material of an apparatus based on the active magnetic regenerator cycle that cools hydrogen gas.