Current Applied Physics, Vol.20, No.6, 794-801, 2020
Enhanced magnetocaloric effect in Eu-doped La0.7Ca0.3MnO3 compounds
Orthorhombic La0.7-xEuxCa0.3MnO3 samples (x = 0.04-0.12) with apparent density of. = 3.9-4.1 g/cm3 prepared by solid-state reactions have been studied. The analysis of temperature-dependent magnetization for an applied field H = 500 Oe indicated a decrease of the Curie temperature (TC) from about 225 K for x = 0.04 through 189 K for x = 0.08-146 K for x = 0.12. The magnetocaloric (MC) study upon analyzing M(H, T) data has revealed that the magnetic entropy change around TC reaches the maximum (|.Smax|), which is dependent on both x and H. For an applied field interval of.H = 60 kOe, |.Smax| values are about 5.88, 4.93, and 4.71 J/ kg center dot K for x = 0.04, 0.08, and 0.12, respectively. Though |.Smax| decreases with increasing x, relative cooling power (RCP) increases remarkably from 383 J/kg for x = 0.04 to about 428 J/kg for x = 0.08 and 0.12. This is related to the widening of the ferromagnetic-paramagnetic transition region when x increases. Particularly, if combining two compounds with x = 0.04 and 0.08 (or 0.12) as refrigerant blocks for MC applications, a cooling device can work in a large temperature range of 145-270 K, corresponding to RCP 640 J/kg for H = 60 kOe. M(H) analyses around TC have proved x = 0.04 exhibiting the mixture of first- and second-order phase transitions while x = 0.08 and 0.12 exhibit a second-order nature. The obtained results show potential applications of Eu-doped La0.7Ca0.3MnO3 materials for magnetic refrigeration below room temperature.