Structural, magnetic and magnetocaloric properties of La0.67Ba0.22Sr0.11Mn1 − xFexO3 nanopowders

Abstract

The influence of Fe-doping on the structural, magnetic and magnetocaloric properties of La0.67Ba0.22Sr0.11Mn1 − xFexO3 perovskite was investigated. These samples were synthesized by Sol–Gel method. X-ray diffraction (XRD) measurements for all samples indicates that all samples, except that with x = 0.2 and 1.0, crystallize in the orthorhombic single-phase with Pnma space group. The Rietveld refinement of the X-ray nanopowder data confirms this result. Room-temperature transmission Mössbauer spectra for all samples except that with x = 1.0 consisted of doublets with similar isomer shift (δ) values consistent with Fe3+ valence state. The spectrum for the sample with x = 1.0 showed the presence of an additional magnetically ordered phase and showed evidence of the presence of Fe4+ valence state. Magnetization measurements versus temperature under magnetic applied field of 0.05 T showed that all of our investigated samples exhibit a paramagnetic–ferromagnetic transition at low temperature except that with x = 1.0. The Curie temperature decreased with increasing Fe content from 345 K for x = 0–80 K for x = 0.3. The magnetic entropy change |ΔSM| for the parent compound was evaluated using Maxwell's relation. The maximum value of the magnetic entropy change obtained from the M(H) plot data is |ΔSMMax| = 2.26 J kg−1 K−1 for applied magnetic field of 5 T. Our result on magnetocaloric properties suggests that the parent sample La0.67Ba0.22Sr0.11MnO3 could be a candidate refrigerant for low temperature magnetic refrigeration.