We report the local-conductivity properties of a ${\text{La}}_{0.8}{\text{Ca}}_{0.2}{\text{MnO}}_3$ thin film, studied by conductive atomic force microscopy. Nonvolatile and bipolar reversible switching of nanometer-sized regions was observed. A threshold voltage, $U_c\approx 3\text{V}$, and a logarithmic pulse-width dependence compatible with domain-wall creep were revealed. The results are difficult to explain in terms of an ionic drift scenario but rather indicate a switching mechanism based on orbital and accompanying structural changes. A phenomenological model of an electric field-induced structural transition is proposed.

• Received 6 May 2010

DOI:https://doi.org/10.1103/PhysRevB.82.144440