Intrinsic Inhomogeneities in Manganite Thin Films Investigated with Scanning Tunneling Spectroscopy

Thin films of ${\mathrm{L}\mathrm{a}}_{0.7}{\mathrm{S}\mathrm{r}}_{0.3}{\mathrm{M}\mathrm{n}\mathrm{O}}_3$ on MgO show a metal insulator transition and colossal magnetoresistance. The shape of this transition can be explained by intrinsic spatial inhomogeneities, which give rise to a domain structure of conducting and insulating domains at the submicrometer scale. These domains then undergo a percolation transition. The tunneling conductance and tunneling gap measured by scanning tunneling spectroscopy were used to distinguish and visualize these domains.