Shot noise of spin-polarized electrons in a single-channel magnetic tunnel junctions

Abstract

Based on the free electron approximation and Egues’ shot noise theory, the shot noise of spin-polarized electrons tunneling in ferromagnetic/semiconductor/ferromagnetic tunnel junctions is studied. Considering the matching of conduction band between ferromagnetic and semiconductor layers, our results show that the Fano factors of spin-polarized electrons have resonant tunneling characteristics when the semiconductor thickness and Rashba spin–orbit coupling strength are increased. When the magnetic moments in two ferromagnetic layers are parallel, with the increase of the molecular field in the ferromagnets, the Fano factor for spin-up electron decreases to zero and then increases exponentially and the Fano factor for spin-down electron is always linear. But when the magnetic moments are antiparallel, the Fano factors for different spin directions tend to be the same. In addition, the Fano factors for different spin directions are almost zero when the incident electron energy is located in the low energy region, but exhibit irregular oscillation when the incident electron energy is located in the high energy region. At the same time, with the variations of the angle of the magnetic moments in two ferromagnetic layers, the electrons Fano factors for different spin orientations show obvious separation characteristics. On the other hand, the conduction band mismatch between ferromagnetic and semiconductor layers is considered, the Fano factors of electrons with different spin directions show obvious difference compared with the results of conduction band matching.