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

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 image 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 50 mT showed that all our investigated samples display a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature TC increases with increasing K content from 278.5 K for x = 0–330 K 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 image in a magnetic field change of 5 T is found to be 6.12, 5.28, 4.92 and 4.26 J kg−1 K−1 for x = 0, 0.05, 0.1 and 0.15 respectively. Large relative cooling power (RCP) value of 258.3 J kg−1 is obtained for La0.8Ag0.05K0.15MnO3 sample, at a field change of 5 T. This relatively large value associated to a Curie temperature of 330 K make the present compound a promising candidate formagneticrefrigerators around room temperature.