  We compute the shot noise in ballistic and disordered Fe/MgO/Fe tunnel
junctions by a wave function-matching method. For tunnel barriers with no more
than 5 atomic layers we find a suppression of the Fano factor as a function of
the magnetic configuration. For thicker MgO barriers the shot noise is
suppressed up to a threshold bias indicating the onset of resonant tunneling.
We find excellent agreement with recent experiments when interface disorder is
taken into account

Materials Science