Influence of Roughness and Disorder on Tunneling Magnetoresistance
  A systematic, quantitative study of the effect of interface roughness and disorder on the magnetoresistance of FeCo$|$vacuum$|$FeCo magnetic tunnel junctions is presented based upon parameter-free electronic structure calculations. Surface roughness is found to have a very strong effect on the spin-polarized transport while that of disorder in the leads (leads consisting of a substitutional alloy) is weaker but still sufficient to suppress the huge tunneling magneto-resistance (TMR) predicted for ideal systems. 
P. X. Xu, V.M. Karpan, K. Xia, M. Zwierzycki, I. Marushchenko, and P.   J. Kelly