Resistance Steps and Asymmetric Conduction Induced by Currents in ${\rm La}_{0.8}{\rm Ca}_{0.2}{\rm MnO}_{3}$ Films

A constant voltage mode of a power supply was adopted to study the current-induced effects in La_0.8Ca_0.2MnO₃ epitaxial thin films. After processed by a current of the density of ~3 × 10⁵ A/cm² for 1 minute, they exhibited anisotropic conduction. Like the behavior of p-n junctions, the current starts to increase dramatically in the forward direction at a threshold voltage (opening voltage Vop), e.g., ~2.3 V at 30 K. For a processing with extending duration, the resistance while processing dropped from 10 k¿ to 2 k¿. Current voltage curves measured following such a step showed more stable asymmetric characteristics and substantial reduction of Vop, which is ~0.8 V at 290 K and ~1.6 V at 50 K. Our results are useful for revealing the origin of asymmetric conduction induced by current and for potential application.