Nonohmic Behaviors and Charge-Ordering Phenomena of La_0.7Ca_0.3MnO₃ Sandwiched by CaMnO₃ Layers

Rare earth manganates exhibit fascinating charge-ordered phases, where interactions between charge carriers and phonons localize carriers on specific lattice sites below a critical temperature. This study investigates thin-film heterostructures of CaMnO 3 (CMO) sandwiching a La 0.7 Ca 0.3 MnO 3 (LCMO) layer, specifically when the LCMO layer narrows to a critical thickness of 12 nm. At the critical thickness and below 120 K, the CMO/LCMO/CMO structure displays nonohmic behaviors in resistivity–temperature (ρ– T ) and current–voltage ( I – V ) curves. This nonohmic behavior is attributed to a breakdown of charge-ordering triggered by applied currents and magnetic fields exceeding a threshold. Our detailed analysis suggests that tensile strain during growth creates oxygen vacancies, particularly at the CMO/LCMO interfaces, which enhance charge-ordering within the confined LCMO layer.