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

Abstract

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 ~31nm and 26nm 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 171K and 78K, 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 1.17Jkg−1K−1 for x=0.1 and 0.44Jkg−1K−1 for x=0.3 for a field change of 2T. The relative cooling power was found to be 80JK−1 and 49JK−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 50K.