Colossal Magnetoresistance in Thick La 0.7 Ca 0.3 MnO 3 Films
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COLOSSAL MAGNETORESISTANCE IN THICK LaO.7CaO. 3 MnO 3 FILMS RANDOLPH E. TREECE,t P. DORSEY, M. RUBINSTEIN, J. M. BYERS, J. S. HORWITZ, E. DONOVAN, AND D. B. CHRISEY Naval Research Laboratory, Washington, DC 20375. ABSTRACT Thick films (0.6 and 2.0 gtm) of the colossal magnetoresistance (CMR) material, La0.7Ca0.3MnO3 (LCMO), have been grown by pulsed laser deposition (PLD). The films were grown from single-phase LCMO targets in 100 mTorr 02 pressures and the material deposited on (100) LaA103 substrates at deposition temperatures of 800C. The deposited films were characterized by X-ray diffraction (XRD), magnetic field-dependent resistivity, and Rutherford backscattering spectroscopy (RBS). The LCMO films were shown by XRD to adopt an orthorhombic structure. Brief post-deposition annealing led to -50,000% and -12,000% MR effect in the 0.6 gtm and 2.0 g.tm films, respectively. INTRODUCTION The magnetoresistive (MR) properties of the substituted lanthanum manganates (La3 +)x(M 2 +)l-xMnO3, where M2 รท=alkaline earth metal, recently have been rediscovered and greatly magnified by the deposition of these compounds in thin film form. The magnetoresistance ratio is defined as AR/RH = (RH - Ro)/RH, where RH is the resistance in an applied magnetic field and RO is the resistance in zero field. Thin films (1000 A
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