Colossal magnetoresistance in doped manganites: A consequence of percolation and phase separation

We report measurements of the resistivity and magnetization of high-quality melt-processed La0.67Ca0.33MnO3 (LCM) and Sr-doped LCM materials that exhi bit a sharp and enhanced metal-insulator transition (T-MI) with significant colossal magnetoresistance (CMR) and two competing magnetic phases in the vicinity of T-MI. Our results can well be explained using percolation in co mbination with the phase-separation scenario proposed for CMR. We propose t hat the spin polarization through grain boundaries and the enhanced grain c onnectivity between the ferromagnetic domains facilitate better percolation through a junction and filament-like resistor network. (C) 2001 American I nstitute of Physics.