EFFECT OF CRYSTALLINITY ON THE MAGNETORESISTIVE PROPERTIES OF LA0.8MNO3-DELTA THIN-FILMS GROWN BY CHEMICAL-VAPOR-DEPOSITION

We report here a study on the role of crystallinity on the magnetoresi stive properties of self-doped La0.8MnO3-delta thin films. Films have been grown by a liquid-source metalorganic chemical vapor deposition t echnique on two different single crystals: SrTiO3 (001) and Al2O3 (012 ) Epitaxial films are obtained on strontium titanate and show a high m agnetoresistance peak at low fields: maximum magnetoresistive effect i n the vicinity of the magnetic transition temperature, and negligible 50 K below. Polycrystalline films are observed on sapphire; they exhib it a lower magnetoresistance of several percent which remains nearly c onstant over a wide temperature range. Two magnetoresistive regimes ca n be distinguished in these films: in low fields (up to 5 mT), a stron g magnetoresistance is obtained with a sensitivity of 0.28%/mT at 78 K ; in higher fields, the magnetoresistance is linear and lower than thi s obtained in epitaxial films. The role of grain boundaries on the mag netoresistive effect is discussed. (C) 1998 American Institute of Phys ics.