Effect of Ag doping on structural, magnetic and magnetocaloric properties of La0.65Ca0.35-xAgxMnO3 manganites

In the present study we report the effect of Ag doping on the structural, magnetic and magnetocaloric properties in La0.65Ca0.35-xAgxMnO3 powder samples synthesized using the solid-state reaction method at high temperature. Powder X-ray patterns have been analyzed by Rietveld method. With increasing Ag amount, a structural transition from orthorhombic (Pbnm space group) to rhombohedral system (R (3) over barc space group) for x > 0.1 has been observed. Magnetization measurements versus temperature in a magnetic applied field of 50 mT showed that all our investigated samples display a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T-C increases with increasing Ag amount from 248 K for x=0-278 K for x=0.2. The magnetic entropy change, deduced from magnetization measurements versus magnetic applied field up to 7 T at several temperatures exhibits a maximum vertical bar Delta S-m vertical bar(max) which decreases with increasing Ag content. vertical bar Delta S-m vertical bar(max) is found to decrease from 1.65 J/kg K for x = 0.05-0.89 J/kg K for x = 0.2 upon a magnetic field change of 1 T while the relative cooling power RCP remains almost constant for all doped samples. (C) 2008 Elsevier B.V. All rights reserved.