Electrical noise as evidence for phase separation in manganites

We review measurements of the electrical noise conducted to study the dynamics of the percolation-like metal-insulator transition in mixed valence manganites. We observed mainly 1/f noise, but in few cases significant random telegraph noise (RTN) in La0.7Ca0.3MnO3 films. The latter originates from two-level (TL) fluctuators which are not related to magnetic domains but exhibit large differences in resistance. The life times of the two states experimentally observed over a broad temperature and field range are analyzed by thermal activation and the net magnetization differences of the states are estimated. These results are related to measurements on Pr0.7Ca0.3MnO3.