Influence of interfacial roughness on the tunnel magnetoresistance

The influence of interfacial roughness on tunnel conductance (TC) and magne toresistance (TMR) are investigated taking into account spin-orbit (SO) cou pling in ferromagnet (FM)/insulator (semiconductor) (I(S))/FM junctions. Ex plicit expressions for spin relaxation are obtained for ballistic and diffu sive transport, respectively. The TC is expressed as the sum of different s pin channels. Spin-flip (SF) scattering due to SO coupling is much stronger for antiparallel alignment of magnetization in the two FMs. The SF scatter ing cause a significant decrease of TMR ratio. We find that surface spin sc attering predominates which suggests that the interfacial states play a key role in the tunnel process. The feature of the reduction of TMR changes wi th the disorder configuration and the SO coupling strength. Resonant TNM oc curs due to the hopping between the SO-split energy levels. (C) 2001 Elsevi er Science B.V. All rights reserved.