Review of magnetocaloric effect in perovskite-type oxides

We survey the magnetocaloric effect in perovskite-type oxides （including doped ABO3-type manganese oxides, A3B2OT-type two-layered perovskite oxides, and A2B＇B＇＇O6-type ordered double-perovskite oxides）. Magnetic entropy changes larger than those of gadolinium can be observed in polycrystalline La1-xCaxMnO3 and alkali-metal （Na or K） doped La0.8Ca0.2MnO3 perovskite-type manganese oxides. The large magnetic entropy change produced by an abrupt reduction of magnetization is attributed to the anomalous thermal expansion at the Curie temperature. Considerable mag- netic entropy changes can also be observed in two-layered perovskites Lal.6Cal.4Mn207 and La2.5-xK0.5＋xMn2O7＋6 （0 〈 x 〈 0.5）, and double-perovskite Ba2Fe1＋xMol-xO6 （0 〈 x 〈 0.3） near their respective Curie temperatures. Com- pared with rare earth metals and their alloys, the perovskite-type oxides are lower in cost, and they exhibit higher chemical stability and higher electrical resistivity, which together favor lower eddy-current heating. They are potential magnetic refrigerants at high temperatures, especially near room temperature.