  We investigate electronic transport in epitaxial Fe(100)/MgO/Fe/MgO/Fe double
magnetic tunnel junctions with soft barrier breakdown (hot spots). Specificity
of these junctions are continious middle layer and Nitrogen doping of the MgO
barriers which provides soft breakdown at biases about 0.5V. In the junctions
with hot spots we observe quasi-periodic changes in the resistance as a
function of bias voltage which point out formation of quantum well states in
the middle Fe continuous free layer. The room-temperature oscillations have
been observed in both parallel and antiparallel magnetic configurations and for
both bias polarizations. A simple model of tunneling through hot spots in the
double barrier magnetic junction is proposed to explain qualitatively this
effect.
