Strong magnetic-field effects in weak manganite-based heterojunction

Oxide heterojunctions were fabricated by growing a La0.67Ca0.33MnO3−δ (LCMO) film on a 0.5 wt % Nb-doped SrTiO3 single crystal (STON). By removing the oxygen of LCMO, a junction with a rather small diffusion/breakdown voltage and junction resistance has been obtained. The most striking observation of the present work is the extremely strong magnetic-field effects in this weak junction. A field of H≈1.7 T can cause an increase of ∼1130% of the diffusion/breakdown voltage and a magnetoresistance as high as R(H)/R(0)−1≈1100%. It is interesting to note that the magnetoresistance is positive, which indicates a basically different mechanism from the manganite, for which a negative magnetoresistance is observed, and could be a result of the change of magnetic and electronic structures of LCMO with respect to STON under magnetic field.