We fabricate micrometric constrictions in manganite epitaxial thin films by atomic force microscope local anodization. We demonstrate the possibility of realizing planar spin valve devices, exhibiting hysteretic transport behavior as a function of the external magnetic field, associated with magnetic domains orientation. We also observe nonlinear current-voltage characteristics which become increasingly linear in external field and we attribute this crossover to the disappearance of energy barriers of domain walls at the constriction