Large tunnel magnetoresistance ratio in Fe/O/NaCl/O/Fe

Abstract

Magnetic tunnel junction (MTJ) is an important device element for many practical spintronic systems. In this paper, we propose and theoretically investigate a very attractive MTJ Fe(001)/O/NaCl(001)/O/Fe(001) as a two-terminal transport junction. By density functional theory total energy methods, we establish two viable device models: one with and the other without mirror symmetry across the center plane of the structure. Large tunnel magnetoresistance ratio (TMR) is predicted from first principles, at over 1800% and 3600% depending on the symmetry. Microscopically, a spin filtering effect is responsible for the large TMR. This effect essentially filters out all the minority spin channels (spin-down) from contributing to the tunnelling current. On the other hand, transport of the majority spin channel (spin-up) having Δ1 and Δ5 symmetry is enhanced by the FeO buffer layer in the MTJ.