Scanning Tunneling Spectroscopy on Pr $_{0.68}$Pb$_{0.32}$ MnO$_{3}$ Single Crystals

Scanning tunneling microscopy/spectroscopy studies were carried out on single crystals of colossal magnetoresistive manganite Pr
_0.68
Pb
_0.32
MnO
₃
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_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 _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