Enhanced relative cooling power of Fe-doped La0.67Sr0.22Ba0.11Mn1-xFexO3 perovskites: Structural, magnetic and magnetocaloric properties

We present the structural and magnetic properties of a novel series of La0.67Sr0.22Ba0.11Mn1-xFexO3 (0 <= x <= 0.3) perovskites prepared by the sol-gel method. These oxides were characterized by x-ray (XRD), neutron powder diffraction (NDP) at room temperature and magnetization measurements versus temperature and various applied magnetic fields. The NPD data, very sensitive to the octahedral tilting, show a crystallographic phase transition from an orthorhombic structure (Pnma) for x = 0 to a rhombohedral structure (R-3c) for Fe-doped samples. Magnetic data show that x = 0 and x = 0.1 perovskites exhibit a paramagnetic-ferromagnetic transition at low temperature, while for 0.2 <= x <= 0.3 a strong divergence between ZFC and FC curves suggest the presence of antagonistic antiferromagnetic and ferromagnetic interactions. The magnetic entropy change (vertical bar Delta S-max vertical bar) takes values of 2.46 J kg(-1) K-1, 2.43 J kg(-1) K-1 and 0.91 J kg(-1) for x = 0, x = 0.1 and 0.2, respectively at 5 T. The relative cooling power (RCP) amounts 169 J Kg(-1), 241 J Kg(-1) and 70 J Kg(-1) at 5 T for x = 0, 0.1, 0.2 respectively. These values are compared favorably with those of some others reported manganites, making La0.67Sr0.22Ba0.11Mn0.9Fe0.1O3 a promising candidate for magnetic refrigeration. (C) 2015 Elsevier B.V. All rights reserved.