  The effect of resonant tunneling on magnetoresistance (MR) is studied
theoretically in a double junction system. We have found that the ratio of the
MR of the resonant peak current is reduced more than that of the single
junction, whereas that of the valley current is enhanced depending on the
change of the discrete energy-level under the change of magnetic field. We also
found that the peak current-valley current (PV) ratio decreases when the
junction conductance increases.
