  We study the magnetic and transport properties of all-manganite
heterostructures consisting of ferromagnetic metallic electrodes separated by
an antiferromagnetic barrier. We find that the magnetic ordering in the barrier
is influenced by the relative orientation of the electrodes magnetization
producing a large difference in resistance between the parallel and
antiparallel orientations of the ferromagnetic layers. The external application
of a magnetic field in a parallel configuration also leads to large
magnetoresistance.
