  Giant Random Telegraph Noise (RTN) in the resistance fluctuation of a
macroscopic film of perovskite-type manganese oxide La2/3Ca1/3MnO3 has been
observed at various temperatures ranging from 4K to 170K, well below the Curie
temperature (TC = 210K). The amplitudes of the two-level-fluctuations (TLF)
vary from 0.01% to 0.2%. We use a statistical analysis of the life-times of the
TLF to gain insight into the microscopic electronic and magnetic state of this
manganite. At low temperature (below 30K) The TLF is well described by a
thermally activated two-level model. An estimate of the energy difference
between the two states is inferred. At higher temperature (between 60K and
170K) we observed critical effects of the temperature on the life-times of the
TLF. We discuss this peculiar temperature dependence in terms of a sharp change
in the free energy functional of the fluctuators. We attribute the origin of
the RTN to be a dynamic mixed-phase percolative conduction process, where
manganese clusters switch back and forth between two phases that differ in
their conductivity and magnetization.
