Abstract
The effects of monovalent doping in the A-site on the structural, magnetic and magnetocaloric properties in La0.5Ca0.45A0.05MnO3 (A = Na, Ag, K) powder perovskite manganites have been investigated. Our compounds have been synthesized using the conventional solid state reaction at high temperature. Rietveled refinements of 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 0.05T indicate that our investigated samples display a paramagnetic- ferromagnetic transition with decreasing temperature. Moreover, in La0.5 Ca0.45Ag0.05MnO3 compound, a second transition toward an antiferromagnetic state is still present around 150K. The Curie temperatures Tc are found to be 270K, 238K and 240K for A = Na, Ag and K respectively. From magnetization measurements versus magnetic applied field we have determined the magnetic entropy change as well as the relative cooling powerRCP for all our samples. The maximum magnetic entropy change , in a magnetic field change of 5T is found to be 1.02, 2.43 and 1.85Jkg/K for A = Na, Ag and K respectively. The La0.5Ca0.45Ag0.05MnO3 sample exhibits the largest RCP value of 217.32 J/kg under 5T.
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