Giant 1/f Noise in Low-Tc CMR Manganites: Evidence of the Percolation Threshold

Abstract

AbstractWe observed a dramatic peak in the 1/f noise at the metal-insulator transition (MIT) in low-Tc, manganites. This many-orders-of-magnitude noise enhancement is observed for both polycrystalline and single-crystal samples of La5/8−y. Pry, Ca3/8MnO3 (y = 0.35 – 0.4) and Pr1−xCaxMnO3 (x = 0.35 – 0.5). This observation strongly suggests that the microscopic phase separation in the low-Tc, manganites causes formation of a percolation network, and that the observed MIT is a percolation threshold. It is shown that the scale of phase separation in polycrystalline samples is much smaller than that in single crystals.