High magnetic entropy change in La0.70Ca0.21Ag0.09MnO3 compound

Abstract

In this work, the structural, electrical, magnetic and magneto-caloric properties of the La0.70Ca0.21Ag0.09MnO3 compound were investigated. The compound was prepared by the sol gel method and sintered at 1000 degrees C for 24 h. Powder X-ray diffraction pattern (XRD) analyzes reveals a single phase orthorhombic structure with the Pnma space group as shown by the Rietveld analysis. The grainy morphology was confirmed with a grain size variation of 0.5-1.5 mu m by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. High resolution transmission electron microscopy (HR-TEM) results strongly support an orthorhombic structure with the parameters calculated from the XRD data. Ferromagnetic-paramagnetic phase transitions occur at similar to 263 K (Curie temperature, TC) and similar to 265 K (metal-insulator, T-MI). The sample undergoes a sharp metaleinsulator transition at TMI following the sharp paramagneticeferromagnetic transition TC. From the isothermal magnetization measurements (M-H), the maximum magnetic entropy change jDSMj was calculated to be similar to 4.8 J/kgK for an applied field change of 1 T, which is greater than that of pure Gd. (C) 2016 Elsevier B.V. All rights reserved.