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 La0.7M0.2M′0.1MnO3 (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 R3̄c space group. Magnetization measurements versus temperature in a magnetic applied field of 50 mT 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 TC and the relative cooling power RCP have been determined. A maximum magnetic entropy change, |ΔSMMax|, of 4.07 Jkg−1 K around 345 K was obtained in La0.7Sr0.2Na0.1MnO3 sample upon a magnetic field change of 5 T. The |ΔSMMax| values of La0.7Ba0.2M′0.1MnO3 are smaller in magnitude compared to La0.7Sr0.2M′0.1MnO3 samples and occur at lower temperatures.