Tunneling-like magnetoresistance in bicrystal La0.8Sr0.2MnO3−δ thin films

Epitaxial ferromagnetic La0.8Sr0.2MnO3−δ films have been sputtered on SrTiO3 bicrystal substrates. Etched patterns crossing the bicrystal grain boundary are compared with identical patterns not crossing it. The films were annealed at different conditions and their magnetoresistance measured as a function of temperature T and of in plane magnetic field H strength and direction. Annealing at 900 °C was found to modify the grain boundary and to increase its magnetoresistance. For H=±80 Oe parallel to the grain boundary and T=32 K narrow magnetoresistance peaks of 60% height are measured. They are interpreted in the frame of an in plane magnetotunneling structure.