Nonlinear transport in tunnel magnetoresistance systems

The nonlinear electronic tunneling through ferromagnet (FM)/insulator (I)/F M single-barrier and FM/I/FM/I/FM double-barrier magnetic layered structure s is studied using the Landauer-Buttiker scattering approach. For the singl e-barrier junctions, the resulting bias dependence of tunnel magnetoresista nce is qualitatively in agreement with experimental observation. The absolu te value of magnetoresistance is shown to be enhanced in the double-barrier systems. Under suitable conditions. large negative and positive magnetores istance effects occur alternately with increasing bias voltage. These featu res make double-barrier resonant-tunnel structures more attractive magnetor esistance devices. [S0163-1829(99)07301-4].