Effect of Fe substitution on structural, magnetic and magnetocaloric properties of nanocrystalline La0.7Te0.3Mn1−xFexO3 (x=0.1, 0.3)

Structural, magnetic and magnetocaloric properties of the nanocrystalline La0.7Te0.3Mn1−xFexO3 (x=0.1 and 0.3) perovskite manganites were investigated prepared by the sol-gel method. X-ray diffraction indicates that the samples crystallize in rhombohedral crystal structure with R3̅c space group for x=0.1 and orthorhombic structure with Pbnm space group for x=0.3. The average crystallite sizes were calculated using Debye Scherer's formula and were found to be ~31 nm and 26 nm for La0.7Te0.3Mn0.90Fe0.1O3 and La0.7Te0.3Mn0.7Fe0.3O3 samples, respectively. The scanning electron microscopy images confirm the homogeneity of the nanocrystalline samples. Temperature dependence magnetization measurements revealed a decrease of ferromagnetic-paramagnetic phase transition with increasing Fe-content. The Curie temperature (TC) determined for x=0.1 and 0.3 are 171 K and 78 K, respectively. Based on the magnetic field dependence of magnetization, M(H), the magnetic entropy change |ΔSM| of the samples were calculated. The maximum entropy change |ΔSmax| values are 1.17 Jkg−1 K−1 for x=0.1 and 0.44 Jkg−1 K−1 for x=0.3 for a field change of 2 T. The relative cooling power was found to be 80 JK−1 and 49 JK−1 for the La0.7Te0.3Mn0.90Fe0.1O3 and La0.7Te0.3Mn0.7Fe0.3O3 samples, which are comparable to other manganites. Tuning of TC with Fe substitution on Mn-site and moderate magnetic entropy change and RCP values, as well as high stability, enable La0.7Te0.3Mn1−xFexO3 (x=0.1 and 0.3) nanocrystalline manganites to be a competitive candidate among the magnetic refrigeration materials for wide temperature ranges from room temperature down to 50 K.