Large two-level magnetoresistance effect in doped manganite grain-boundary junctions

We performed a systematic analysis of the tunneling magnetoresistance (TMR) effect in single grain-boundary junctions formed in epitaxial La_2/3Ca_1/3MnO₃ films deposited on SrTiO₃ bicrystals. For magnetic fields H applied parallel to the grain-boundary barrier, an ideal two-level resistance switching behavior with sharp transitions is observed with a TMR effect of up to 300% at 4.2 K and still above 100% at 77 K. Varying the angle between H and the grain boundary results in differently shaped resistance vs H curves. The observed behavior is explained within a model of magnetic domain pinning at the grain-boundary interface.