Review of magnetocaloric effect in perovskite-type oxides

We survey the magnetocaloric effect in perovskite-type oxides (including doped ABO(3)-type manganese oxides, A(3)B(2)O(7)-type two-layered perovskite oxides, and A(2)B'B '' O-6-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 magnetic entropy changes can also be observed in two-layered perovskites La1.6Ca1.4Mn2O7 and La2.5-xK0.5+xMn2O7+delta (0 < x < 0.5), and double-perovskite Ba2Fe1+xMo1-xO6 (0 <= x <= 0.3) near their respective Curie temperatures. Compared 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.