The theory analysis of the field dependence of the magnetoresistance of La0.7Ca0.3MnO3 film

The field dependence of the magneto resistance of the magnetic perovskite L a0.7Ca0.3MnO3 film has been analyzed by using a negative-magnetoresistivity scaling deduced from Mott's model. The fitting is made and the Curie tempe rature is deter-mined more precisely. Through analyzing the variation of th e magnetoresistance (MR) with respect to some physics parameters, the relat ions between the value of MR ratio and the size of the magnetically aligned cluster are revealed. Moreover, the behaviors of the fit parameters J(T) a nd the magnetically aligned clusters are investigated. We find that with th e paramagnetic-ferromagnetic transition a sudden change in the value of J(T ) and in the size of the magnetically aligned clusters occurs. (C) 2001 Pub lished by Elsevier Science B.V.