Large two-level magnetoresistance effect in doped manganite grain-boundaryjunctions

We performed a systematic analysis of the tunneling magnetoresistance (TMR) effect in single grain-boundary junctions formed in epitaxial La2/3Ca1/3Mn O3 films deposited on SrTiO3 bicrystals. For magnetic fields H applied para llel to the gain-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 o bserved behavior is explained within a model of magnetic domain pinning at the grain-boundary interface.