Structure and magnetocaloric properties of La0.8Ag0.2−xKxMnO3 perovskite manganites

Abstract

In the present study we report the effect of K doping on the structural, magnetic and magnetocaloric properties in La0.8Ag0.2−xKxMnO3 (0≤x≤0.15) powder samples synthesized using the solid state reaction method at high temperature. X-ray diffraction analysis using Rietveld refinement show that all our samples crystallize in the rhombohedral structure with R3¯c space group. The surface morphology and elemental analysis of both samples were carried out by scanning electron microscopy (SEM) and energy dispersive X-ray technique (EDX), respectively. Magnetization measurements versus temperature in a magnetic applied field of 50mT showed that all our investigated samples display a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature TC increases with increasing K content from 278.5K for x=0–330K for x=0.15. A large magnetic entropy change |ΔSM|, deduced from isothermal magnetization curves, has been observed in our samples with a peak centered around their respective TC. The maximum of the magnetic entropy change |ΔSMMax| in a magnetic field change of 5T is found to be 6.12, 5.28, 4.92 and 4.26Jkg−1K−1 for x=0, 0.05, 0.1 and 0.15 respectively. Large relative cooling power (RCP) value of 258.3Jkg−1 is obtained for La0.8Ag0.05K0.15MnO3 sample, at a field change of 5T. This relatively large value associated to a Curie temperature of 330K make the present compound a promising candidate formagneticrefrigerators around room temperature.