Effects of Fluorination on the Structural and Electrical Properties of Epitaxial La_0.67Ca_0.33MnO_3-y Thin Films

We have studied the effects of fluorination (i.e. fluorine incorporation into the material) on the structural and electrical properties of epitaxial thin films of the hole doped rare earth manganese oxide La_0.67Ca_0.33MnO_3-y (LCMO). Flourination is known to alter the electronic properties of other ABO3-y materials such as SrFeO3-y where fluorine occupies the oxygen vacancy sites forming an oxy-fluoride structure. Our preliminary results in LCMO indicate similar changes in the lattice structure and electrical conductivity upon fluorination, the effects being more pronounced in films grown under oxygen-poor conditions using pulsed laser deposition. These changes are highly temperature dependent with the fluorinated samples exhibiting metal insulator transitions that previously were not present.