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. (c) 2004 Elsevier B.V. All rights reserved.