High magnetic entropy change in La_0.70Ca_0.21Ag_0.09MnO₃ compound

In this work, the structural, electrical, magnetic and magneto-caloric properties of the La_0.70Ca_0.21Ag_0.09MnO₃ 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, T_C) and ∼265 K (metal-insulator, T_MI). The sample undergoes a sharp metal–insulator transition at T_MI following the sharp paramagnetic–ferromagnetic transition T_C. From the isothermal magnetization measurements (M−H), the maximum magnetic entropy change |ΔS_M| was calculated to be ∼4.8 J/kgK for an applied field change of 1 T, which is greater than that of pure Gd. - Highlights: • XRD analysis reveals that the La_0.70Ca_0.21Ag_0.09MnO₃ has orthorhombic structure belonging to the Pnma space group. • Average grain size distribution was found between 0.5 to 1.5 μm. • The maximum magnetic entropy change of La_0.70Ca_0.21Ag_0.09MnO₃ is higher than that of pure Gd (2.8 J/kgK in a magnetic field change of 1 T). • The Curie temperature of the compound was found to be 263 K. • XRD and TEM results were found to coinciding each other.