Interfacial Effects in Spin Transport in Magnetic Tunnel Junctions

We have been looking at the spin-dependent tunneling in magnetic tunnel junctions (MTJ) using a position-dependent effective-mass Hamiltonian. Current-voltage curves and TMR values are calculated based upon analytical results, and include multiple band-to-multiple-band tunneling, to capture more realistically the main features of the band structure in cobalt and iron. The sign of the spin-current polarization is an outstanding issue in the field, and we believe that interfacial effects play a significant role. We have carried out DFT simulations of Co/Al$_{2}$O$_{3}$/Co structures, assuming Al-termination at the interface, which show significant changes in the LDOS at the interface as compared to bulk. For simulations that include disorder at the interface, there is a change in spin-polarization of the LDOS, due to interfacial scattering and screening effects, going across the interface from the Co to the Al layer. This change in spin-polarization is reflected in our calculated I-V curves and TMR values.