Improvement of electromagnetic properties at room temperature in La0.625Ca0.375-Sr MnO3:Ag0.2 (x = 0.09–0.15) ceramics by Sr doping

Abstract

Abstract In this study, facile sol-gel method was used to prepare La0.625Ca0.375-xSrxMnO3:Ag0.2 (LCSMO:Ag0.2, x = 0.09–0.15) polycrystalline ceramics. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) indicated an increase in grain size of LCSMO:Ag0.2 ceramics with orthorhombic structure as a function of x. Four-probe resistivity temperature system was employed to characterize electrical and magnetic properties of all prepared specimens. Temperature coefficient of resistivity (TCR) and magnetoresistance (MR) yielded room temperature maxima of 4.9% K−1 at 299.2 K and 17.5% at 299.1 K. The enhancement in TCR and MR was mainly attributed to Jahn-Teller (JT) distortion and double exchange (DE) effect. X-ray photoemission spectroscopy (XPS) and inductively coupled plasma-optical emission spectrometer (ICP-OES) all confirmed the existence of silver in metallic forms and the increase of Sr content. On the other hand, satellite peaks in low-temperature range of resistivity-temperature (ρ-T) curves gradually weakened as Sr-doped amount increased. The fitting of ρ-T curves in low-temperature region revealed that gradual vanishing of satellite peak may be due to presence of Sr, able of inhibiting various types of interactions: electron-electron, electron-phonon, and Kondo-like spin-dependent scattering. Overall, room temperature TCR and MR were both optimized by Sr doping, providing further understanding of CMR mechanism and application of manganite materials in electromagnetic equipment under room temperature.