Crossover from negative to positive magnetoresistance in La0.7Ce0.3MnO3-SrTiO3-Nb heterojunctions -: art. no. 032501

A crossover from negative to positive magnetoresistance (MR) is observed in the heterojunction composed of a La0.7Ce0.3MnO3 film and a 0.5 wt. % Nb-doped SrTiO3 substrate. The temperature and bias current dependences of MR sign in the junction are investigated carefully. It is found that the positive MR occurs when temperature or applied bias current is increased to a higher value. The relation between MR and an external magnetic field is also found to be temperature dependent. We attribute the appearance of the positive MR at higher temperatures to the tunneling transport mechanism. These results are helpful in configuring artificial devices using manganite-based heterojunctions. (c) 2005 American Institute of Physics.