Abstract
A detailed investigation of the magnetic and the magnetocaloric properties of La0.7Sr0.3MnO3, La0.7Ca0.3MnO3 and La0.7Ca0.1Sr0.2MnO3 for possible application in magnetic refrigeration is presented. The adiabatic magnetic entropy change was determined for a magnetic field change from 0 to 2.5 T by using magnetization data. A broad table-like entropy change with a relative cooling power of 111 J/kg in an applied magnetic field of 2.5 T with an operating temperature range of 54 K was observed in the La0.7Ca0.1Sr0.2MnO3 sample. The broadening in the magnetic entropy change in La0.7Ca0.1Sr0.2MnO3 is discussed in light of the tricritical mean-field theory. The tricritical exponent (delta) was calculated for the La0.7Ca0.1Sr0.2MnO3 sample and found to be similar to 4.76 +/- 0.03, which is very close to the proposed value delta = 5 for the tricitical exponent. The studied samples can be considered as giant magnetocaloric materials for room-temperature refrigeration.