Large magnetocaloric effect in lanthanum-deficiency manganites La0.8−x□xCa0.2MnO3 (0.00≤x≤0.20) with a first-order magnetic phase transition

Abstract

Lanthanum-deficiency effect on the magnetic and magnetocaloric properties of La0.8−x□xCa0.2MnO3 (0.00≤x≤0.20) polycrystalline samples has been investigated using X-ray diffraction and magnetization measurements. The structural characterization has revealed that all samples are crystallized in the orthorhombic structure with Pnma space group. From magnetic measurement a first-order magnetic phase transition from ferromagnetic to paramagnetic state is observed at the Curie temperature (TC) which is found to increase from 236.5 to 247K when lanthanum-deficiency rate increases. Besides, both magnetocaloric effect (MCE) and relative cooling power (RCP) has been estimated. As important result, the values of MCE and RCP in our managanite with Lanthanum-deficiency are reported to be near to those found in the gadolinium considered as magnetocaloric material reference. Finally, the first-order magnetic phase transition has been confirmed by the construction of the universal curve of the magnetic entropy change.