Magnetically Correlated Schottky Barrier in the La1.8Ca1.2Mn2O7 Double-Layered Perovskite Ceramic

Double-layered La1.8Ca1.2Mn2O7 sample with a perovskite structure was synthesized by solid state reaction and electrical transport properties were investigated using 4-wire direct current (DC) and 2-wire alternating current (AC) measurement methods. The result reveals that the I-V characteristic of the La1.8Ca1.2Mn2O7 ceramic exhibits a linear behaviour above Curie temperature (TC) while it shows a strong nonlinearity below TC. The nonlinear coefficient increases with decreasing temperatures and reaches a maximum of 60.5 at 14 K for the limit of the experiment. We believe that a magnetically correlated Schottky barrier forming at the grain boundary is the main factor to control the transport properties for the La1.8Ca1.2Mn2O7 ceramic.