Quantum effects in atomically perfect specular spin valve structures

Abstract

A simple tight-binding theoretical model is proposed for spin-dependent, current-in-planetransport in highly coherent spin valve structures under specularity conditions. Usingquantum-mechanically coherent and spatially quantized Fermi states in the consideredmultilayered system, a system of partial Boltzmann kinetic equations is built for relevantsubbands to yield the expressions for conductance in parallel or antiparallel spinvalve states and thus for the magneto-conductance. It is shown that specularityfavors the magnetoresistance for this structure reaching a high value (very close to100%). This result is practically independent of the model parameters, in particular it does noteven need that the lifetimes of majority and minority carriers be different (as necessary forthe quasiclassical regimes). The main MR effect in the considered limit is due to thetransformation of coherent quantum states, induced by the relative rotation ofmagnetization in the FM layers. Numerical calculations based on the specific Boltzmannequation with an account of spin-dependent specular reflection at the interfaces is alsoperformed for a typical choice of material parameters.