Electroresistance and electronic phase separation in mixed-valent manganites

The sensitivity of transport in colossal magnetoresistance (CMR) manganites to external electric and magnetic fields is examined using field effect configurations with La0.7Ca0.3MnO3 (LCMO), Na0.7Sr0.3MnO3, La0.7Ba0.3MnO3, and La0.5Ca0.5MnO3 (0.5-doped LCMO) channels, and ferroelectric PbZr0.2Ti0.8O3 (PZT) or dielectric (SrTiO3) gates. A large electroresistance (ER) of similar to 76% at 4 X 10(5) V/cm is found in LCMO with PZT-ferroelectric gate, but the magnitude of the effect is much smaller (a few percent) in the other three channels. The ER and CMR effects are remarkably complimentary. The size and systematics of the effect strongly favor a percolative phase separation picture.