Rotation of ferromagnetic clusters induced magnetoresistance in the junction composed of La_0.9Ca_0.1MnO_3+\delta and 1 wt.% Nb-doped SrTiO₃

A junction composed of ultrathin La_0.9Ca_0.1MnO_{3 +\delta} (LCMO) film and 1 wt.% Nb-doped SrTiO_3 was fabricated and its magnetoresistance (MR) was studied and compared with LCMO film. It was found that the resistance of the junction has a similar dependence on magnetic field as that of the LCMO film: the curvature of R--H curves is upward above Curie temperature (T_\rm C) and downward below T_\rm C. These behaviours strongly suggest that the rotation of ferromagnetic clusters in manganite also causes MR in the corresponding junction. This MR can be qualitatively understood by the change of the width of the barrier induced by the rotation of ferromagnetic clusters. These results suggest a possibility to obtain junctions with large low-field MR.