Abstract :
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 Tc(H)=Tc(0)+aH−bH2. The change of the curvature of the magnetoresistance curves ρ(H) from positive below Tc to negative above Tc shows two different conduction mechanisms above and below Tc. The temperature dependence of the resistivity above Tc 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.
