Large magnetic entropy change above 300 K in manganites

An investigation into the magneto-caloric effect in several compounds: (La065Sr0.35MnO3)-Sr-., La0.6Sr0.2Ca0.2MnO3, La0.6Sr0.2Ba0.2MnO3, La0.7Ba0.3MnO3 and La0.7Ba0.24Ca0.06MnO3 was carried out. Among the compositions investigated, La0.6Sr0.2Ba0.2MnO3 has the highest value, at 2.26 J/kg/K, for \ DeltaS(M)(max) \ at T-C = 354 K, with 10 kOe applied field. The adiabatic temperature change, DeltaT(ad), of this sample is estimated to be similar to1.1 K and similar to4.95 K with fields of 10 kOe and 50 kOe, respectively. Since a significant change in magnetic entropy of the present compounds has been found to occur around 300 K, these materials are attractive candidates for room-temperature magnetic refrigeration applications. The large magnetic entropy change in the manganese perovskites must have originated from the abrupt reduction of magnetization which is associated with the ferromagnetic to paramagnetic transition at the Curie temperature.