Effect of Monovalent Doping on the Structural, Magnetic and Magnetocaloric Properties in La0.7M0.2M'0.1MnO3 Manganese Oxides (M=Sr, Ba and M'=Na, Ag, K)

Structural, magnetic and magnetocaloric effects of powder perovskite manganites La(0.7)M(0.2)M'(0.1)MnO(3) (M=Sr, Ba and M'=Na, Ag and K) have been investigated. Our samples have been elaborated using the conventional solid state reaction at high temperature. X-Ray diffraction characterizations showed that all our synthesized samples crystallize in the distorted rhombohedral system with R3c space group. Magnetization measurements versus temperature in a magnetic applied field of 50mT showed that all our samples are ferromagnetic above room temperature. From the measured magnetization data of our synthesized samples as a function of magnetic applied field, the associated magnetic entropy change close to their respective Curie temperature T(C) and the relative cooling power RCP have been determined. A maximum magnetic entropy change, vertical bar Delta S(M)(Max)vertical bar, of 4.07Jkg(-1)K(-1) around 345K was obtained in La(0.7)M(0.2)M'(0.1)MnO(3) sample upon a magnetic field change of 5T. The vertical bar Delta S(M)(Max)vertical bar values of La(0.7)M(0.2)M'(0.1)MnO(3) are smaller in magnitude compared to La(0.7)M(0.2)M'(0.1)MnO(3) samples and occur at lower temperatures. (c) 2009 Elsevier B.V. All rights reserved