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Giant Peak of the 1/f Noise at the Metal-Insulator Transitions in Low-Tc CMR Manganites: Evidence of the Percolation Threshold at Tc

V. Podzorov, M. Uehara, M. E. Gershenson, S-W. Cheong

cond-mat.str-elarXiv:cond-mat/9912064

Abstract

We 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-yPryCa3/8MnO3 (y=0.35-0.4) in zero magnetic field and Pr1-xCaxMnO3 (x=0.35-0.5) in magnetic field. 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.

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