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

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 °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 μm 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 ∼263 K (Curie temperature, TC) and ∼265 K (metal-insulator, TMI). The sample undergoes a sharp metal-insulator transition at TMI following the sharp paramagnetic-ferromagnetic transition TC. From the isothermal magnetization measurements (M−H), the maximum magnetic entropy change |ΔSM| was calculated to be ∼4.8 J/kgK for an applied field change of 1 T, which is greater than that of pure Gd.