Giant tunneling magnetoresistance in ferromagnet/ insulator (semiconductor) coupling double-tunnel-junction subjected to electric field

Based on the two-band model, a transfer-matrix treatment of the tunnel conductance and magnetoresistance is presented for tunneling through ferromagnet/insulator (semiconductor) double-junction subjected to dc bias. There exist the spin polarized resonant tunneling and the giant tunnel magnetoresistance. The highest value of the magnetoresistance in double-junction can reach 90%. It is expected that these results can cause the interest in experimental efforts in designing spin polarized resonant tunneling devices. Our theories can also be extended to the single-junction and the superlattice easily. For the single-junction, our results are qualitatively in agreement with the experimental measurements.