Magnetotransport and hysteretic behavior in epitaxial La_0.67Ca_0.33MnO_3-δ films

We have fabricated epitaxial La0.67Ca0.33MnO3-δ thin films using pulsed laser deposition and performed subsequent thermal treatments. Magnetoresistance values as large as 14 000% (Δρ/ρH) 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. © 1996 American Institute of Physics.