  We investigate electronic transport through II-VI semiconductor resonant
tunneling structures containing diluted magnetic impurities. Due to the
exchange interaction between the conduction electrons and the impurities, there
arises a giant Zeeman splitting in the presence of a moderately low magnetic
field. As a consequence, when the quantum well is magnetically doped the
current-voltage characteristics shows two peaks corresponding to transport for
each spin channel. This behavior is experimentally observed and can be
reproduced with a simple tunneling model. The model thus allows to analyze
other configurations. First, we further increase the magnetic field, which
leads to a spin polarization of the electronic current injected from the leads,
thus giving rise to a relative change in the current amplitude. We demonstrate
that the spin polarization in the emitter can be determined from such a change.
Furthermore, in the case of a magnetically doped injector our model shows a
large increase in peak amplitude and a shift of the resonance to higher
voltages as the external field increases. We find that this effect arises from
a combination of giant Zeeman splitting, 3-D incident distribution and broad
resonance linewidth.
