Electrical transport properties in magnetoresistive La0.67Ca0.33MnO3 thin film

We have measured electrical transport properties of magnetoresistive La0.67Ca0.33MnO3 thin film as a function of temperature and magnetic field. The suppression of the resistivity and the shift of the resistivity peak toward higher temperature caused by increasing magnetic field were understood in terms of magnetic field-induced ferromagnetic ordering. The field dependence of peak temperature of resistivity can be fitted by the expression T-c(H) = T-c(0) + aH - bH(2). The change of the curvature of the magnetoresistance curves rho(H) from positive below T-c to negative above T-c shows two different conduction mechanisms above and below T-c. The temperature dependence of the resistivity above T-c exhibits a thermally activated behavior relative to the applied magnetic field. The Hall effect in different magnetic fields shows that the negative magnetoresistance effect results from the increase of charge carrier density induced by the magnetic field. (C) 2000 Elsevier Science Ltd. All rights reserved.