Low field magnetotransport in La0.7Sr0.3MnO3 films

We have observed a strong correlation between the degree of epitaxy and the low field resistance versus field R(H) behavior in highly textured La0.7Sr 0.3MnO3 films grown by pulsed laser deposition on SrTiO3 substrates. Highly epitaxial films show a small temperature dependent low field hysteretic R( H) peak near the magnetic ordering temperature (T-c), when the applied fiel d is parallel to the transport current (J parallel to H). In contrast, film s with reduced epitaxy show a much larger low field hysteretic R(H) behavio r with a pronounced in-plane angular dependence. The magnitude of this resp onse grows with decreasing temperature below T-c. Our data and analysis sug gest that even low angle grain boundaries play a fundamental role in transp ort properties in colossal magnetoresistive materials. (C) 1998 American In stitute of Physics. [S0021-8979(98)26611-4].