  Thin films of La0.7Sr0.3MnO3 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.
