A phenomenological description of temperature dependence of magnetoresistance in La 2/3Ca1/3MnO3-δ thin films

The electrical resistance in zero magnetic field and magnetoresistance in different external magnetic fields have been measured in a temperature range of 77-300 K. It is found that the temperature dependence of magnetoresistance can be well described by a phenomenological formula of ρ(T)=(1σ(T)= (1α(M/M s) 2+βexp(-E 0/k BT), where the fitting parameters α,β vary as the external magnetic field H changes, E 0 is the activation energy, E 0/k B =1160 K, M s is the saturation magnetization, the temperature and magnetic field dependence of M/M s is obtained by the mean-field expression.