Magnetotransport and hysteretic behavior in epitaxial La0.67Ca0.33MnO3-delta films

We have fabricated epitaxial La0.67Ca0.33MnO3-delta thin films using pulsed laser deposition and performed subsequent thermal treatments. Magnetoresistance values as large as 14000% (Delta rho/rho(H)) were obtained. Above magnetic ordering temperatures, we observed a thermally activated conductivity that also has a quadratic magnetic field dependence. At low temperatures, we found a large hysteresis in the magnetoresistance that correlates with an unusual magnetic hysteresis curve. We interpret the hysteretic behavior as the result of a ''frozen-in'' canted spin structure. Our results suggest that the electron conduction in this material is most sensitive to the canting angle of the neighboring Mn spins. (C) 1996 American Institute of Physics.