Scanning Tunneling Spectroscopy on Pr 0.68Pb0.32 MnO3 Single Crystals

Scanning tunneling microscopy/spectroscopy studies were carried out on single crystals of colossal magnetoresistive manganite Pr_0.68Pb_0.32MnO₃ at different temperatures in order to probe their spatial homogeneity across the metal-insulator transition temperature T_M-I(~255K). A metallic behavior of the local conductance was observed for temperatures T<T_M-I. Zero bias conductance (dI/dV)_V=0, which is directly proportional to the local surface density of states at the Fermi level, shows a single distribution at temperatures T< 200 K suggesting a homogeneous electronic phase at low temperatures. In a narrow temperature window of 200 K <T<T_M-I, however, an inhomogeneous distribution of (dI/dV)_V=0 has been observed. This result gives evidence for phase separation in the transition region in this compound