Effect of Calcium Deficiency on the Structural, Magnetic and Magnetocaloric Properties in La0.65Ca0.35MnO3 Manganites Oxides

Abstract

We present in this paper the effect of calcium deficiency on the structural, magnetic and magnetocaloric in La0.65Ca $_{0.35-\mathrm {x}}\square _{\mathrm {x}}$ MnO3 (x =−0.15) powder samples. Our compounds were prepared using the solid-state reaction at high temperatures. Rietveld analysis show that all our synthesized samples are single phase without any detectable impurity and crystallize in the orthorhombic system with Pbnm space group. The Mn atom is coordinated by six oxygen atoms forming an irregular octahedron. The scanning electron microscopy (SEM) micrographs reveal that all the structure is characterized by various shapes and a uniform grain size which clearly increase from 1.528 μm for x = 0 to 3.36 μm for x = 0.1. Magnetic measurements as a function of temperature show that all our samples exhibit a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature exhibits a minimum of 228 K for x = 0.10. The maximum value of the relative cooling power RCP is obtained for x = 0.15 and is found to be 270 J/kg under a magnetic field change of 5 T and which is around 65 % of that observed for pure gadolinium known as the best material for magnetic refrigeration near room temperature.