Effect of crystallinity on the magnetoresistive properties of La0.8MnO3-δ thin films grown by chemical vapor deposition

We report here a study on the role of crystallinity on the magnetoresistive properties of self-doped La0.8MnO3-delta thin films. Films have been grown by a liquid-source metalorganic chemical vapor deposition technique on two different single crystals: SrTiO3 (001) and Al2O3 (012) Epitaxial films are obtained on strontium titanate and show a high magnetoresistance peak at low fields: maximum magnetoresistive effect in the vicinity of the magnetic transition temperature, and negligible 50 K below. Polycrystalline films are observed on sapphire; they exhibit a lower magnetoresistance of several percent which remains nearly constant over a wide temperature range. Two magnetoresistive regimes can be distinguished in these films: in low fields (up to 5 mT), a strong magnetoresistance is obtained with a sensitivity of 0.28%/mT at 78 K; in higher fields, the magnetoresistance is linear and lower than this obtained in epitaxial films. The role of grain boundaries on the magnetoresistive effect is discussed. (C) 1998 American Institute of Physics.