The sensitivity of transport in colossal magnetoresistance (CMR) manganites to external electric and magnetic fields is examined using field effect configurations with La(0.7)Ca(0.3)MnO(3) (LCMO), Na(0.7)Sr(0.3)MnO(3), La(0.7)Ba(0.3)MnO(3), and La(0.5)Ca(0.5)MnO(3) (0.5-doped LCMO) channels, and ferroelectric PbZr(0.2)Ti(0.8)O(3) (PZT) or dielectric (SrTiO(3)) gates. A large electroresistance (ER) of approximately 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.

Epitaxial thin films of ordered double-perovskite Sr2FeMoO6−y are deposited on (001) SrTiO3 substrates by pulsed-laser deposition using a two step growth process. Selection of growth conditions is found to lead to either highly conductive metallic thin films (residual resistivity of about 1 μΩ cm) or semiconducting films. The metallic films show a positive magnetoresistance (MR) as high as 35%, while the semiconducting films show a negative MR of −3%, at a temperature of 5 K and a field of 8 T.

We grow Pb(Zr,Ti)0 3 (001)/Lai.,CaxMnO3 (001) hetereostructure epitaxially on Nb doped STO substrate using pulsed laser ablation. A field effect device configuration is formed with the manganite as the channel and the Nb:STO substrate as the gate. Channel resistance modulation by the gate pulsing is studied both with and without magnetic field. We not only find a remarkably large electroresistance effect of 76% at 4x I0 5 V/ cm, but also the complimentarity of this ER effect with the widely studied CMR effect. The large size of this effect and the complimentarity of ER and MR effects strongly suggest a percolative phase separated picture of manganites.

We report microwave absorption measurements as a function of temperature ͑from 290 to 125 K͒ and magnetic field ͑from 0 to 0.3 T͒ in mm-thick parallelepipeds of sintered V 2 O 3 and V 2 O 3 containing micron-size Fe precipitates. As before, it turns out that near the metal-insulator ͑MI͒ transition, the loss exhibits a sharp peak as a function of temperature. On application of a magnetic field, the peak temperature for (V 2 O 3 ϩFe) changes by a few kelvin, causing a giant magnetoimpedance ͑Ϸ 200% in 0.1 T field͒ in the neighborhood of the MI transition.