Anomalous temperature and magnetic field dependences of current?voltage characteristics in Pr0.6Ca0.4MnO3/Nb-doped SrTiO3 heterojunctions

The effect of a magnetic field on the current–voltage characteristics of Pr0.6Ca0.4MnO3/Nb-doped SrTiO3 heterojunctions was studied. An abnormal increase in diffusion voltage, break down voltage and ideality factor was observed at a low temperature. It was also found that the transport properties of these heterojunctions could be considerably influenced by external magnetic fields. When a magnetic field was applied, I–V curves were shifted to a lower bias voltage. Both ideality factor and saturation current were affected by the magnetic field. The magnetic field modulation was more significant at lower temperatures. The analysis showed that the current–voltage relation was dominated by tunnelling. The anomaly at low temperatures may be a result of temperature and electric field dependence of the dielectric constant of Nb : SrTiO3. A magnetic field may also modify the work function and density of states of Pr0.6Ca0.4MnO3, leading to a change in current–voltage characteristics.