Magnetic and magnetocaloric properties of monovalent substituted La 0.65Ca0.3M0.05MnO3 (M=Na, Ag, K) perovskite manganites

Abstract

The effects of monovalent doping in the A-site on the structural, magnetic and magnetocaloric properties in La0.65Ca0.3M 0.05MnO3 (M=Na, Ag, K) powder perovskite manganites have been investigated. Our samples have been synthesized using the conventional solid state reaction at high temperature. Rietveld refinements of the X-ray diffraction patterns at room temperature show that all our powder samples are single phase and crystallize in the orthorhombic structure with Pbnm space group. Magnetization measurements versus temperature in a magnetic applied field of 50mT indicate that our investigated samples display a paramagnetic- ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to be 295K, 254K and 285K for M=Na, Ag and K respectively. From the measured magnetization data of La0.65Ca 0.3M0.05MnO3 (M=Na, Ag, K) samples as a function of magnetic applied field, the associated magnetic entropy change close to their respective Curie temperature TC and the relative cooling power RCP have been determined. The maximum magnetic entropy change, |ΔSmaxm|, in a magnetic field change of 5T is found to be 3, 5.16 and 3.54 Jkg/K for M=Na, Ag and K respectively. The La 0.65Ca0.3K0.05MnO3 sample exhibits the largest RCP value of 295J/kg. © 2009 IOP Publishing Ltd.