Magnetic entropy change larger than that of gadolinium has been observed in polycrystalline of ${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_3$ ( $x=0.2\mathrm{}$ and 0.33) perovskite-type manganese oxide. The large magnetic entropy change produced by the abrupt reduction of magnetization is attributed to the anomalous thermal expansion just at the Curie temperature. The considerable magnetic entropy change was also observed in ${\mathrm{La}}_{0.75}{\mathrm{Sr}}_{0.25-y}{\mathrm{Ca}}_y{\mathrm{MnO}}_3$ near room temperature. The phenomenon of large magnetic entropy change and the convenient adjustment of the Curie temperature make the perovskite-type manganese oxides useful for magnetic refrigerants in an extended high temperature range even at room temperature.

• Received 5 November 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.1142