Magnetic properties and magnetocaloric effect in La0.7Sr0.3−xBixMnO3 manganites

Abstract

Structural properties, magnetization and magnetocaloric effect measurements in the compounds based on lanthanum–strontium–bismuth manganites La0.7Sr0.3−xBixMnO3 (LSBiMO) with 0.05⩽x⩽0.30 have been performed. The valence states of elements entering into the composition of investigated LSBiMO samples were analyzed for x=0.15 and 0.3 using the HR XPS spectra of Bi 4f, La 3d, Mn 3s and Sr 3d. According to X-ray powder diffraction data the crystalline structure of the samples is perovskite-like with a small rhombohedral distortion. The a and c lattice parameters and unit cell volume V are established to increase with increasing Bi content. All the manganites show ferromagnetic-like ordering with second order phase transition to paramagnetic state. The Curie temperature and magnetization decrease at substitution of Sr2+ for Bi3+ ions. The magnetic entropy changes were calculated using the field dependence of isothermal magnetization in the terms of the thermodynamic Maxwell relation. The maximum magnetic entropy change value was shown to be 0.94Jkg−1K−1 for x=0.05 for a field change of 1T.