  We investigate the spin-polarized transport properties of a two-dimensional
electron gas in a n-type diluted magnetic narrow gap semiconductor quantum well
subjected to a perpendicular magnetic and electric field. Interesting beating
patterns in the magneto resistance are found which can be tuned significantly
by varying the electric field. A resonant enhancement of spin-polarized current
is found which is induced by the competition between the s-d exchange
interaction and the Rashba effect [Y. A. Bychkov and E. I. Rashba, J. Phys. C
17, 6039 (1984)].
