Influence of Ag doping on electrical and magnetic properties of La0.67Ca0.33MnO3 polycrystalline ceramics

Abstract

Structural, electrical, and magnetic properties of La0.67Ca0.33MnO3 with Ag doped (LCMO:Agx, 0 ≤ x ≤ 0.5) polycrystalline ceramics were studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM), four-probe resistance-temperature measurements (RT), X-ray photoemission spectroscopy (XPS), and vibrating sample magnetometry (VSM). Significant improvements in temperature coefficient of resistance (TCR) and magnetoresistance (MR) were observed in LCMO:Agx (x = 0.2) samples on addition of Ag. TCR and MR reached maximum values of 26.0% K−1 (269.5 K) and 47.4% (271.8 K) respectively, for x = 0.2. Interestingly, XPS along with XRD and SEM results indicated that silver existed in LCMO:Agx composites in two forms, at A sites (La3+/Ca2+) as Ag+ ion and segregated at grain boundaries (GBs) as metallic silver. All evidences supported the fact that Ag doping was beneficial in improving the electrical and magnetic transport properties of LCMO:Agx ceramics. Hence, they can be used in infrared detectors or magnetic sensor devices. Double-exchange (DE) mechanism and Jahn-Teller (JT) distortion were used to explain the optimal physical performance of LCMO ceramics with Ag doping.