  We measured the shot noise in fully epitaxial Fe/MgAl2OX/Fe-based magnetic
tunneling junctions (MTJs). While the Fano factor to characterize the shot
noise is very close to unity in the antiparallel configuration, it is reduced
to 0.98 in the parallel configuration. This observation shows the
sub-Poissonian process of electron tunneling in the parallel configuration,
indicating the coherent tunneling through the spinel-based tunneling barrier of
the MTJ.
