Dependence of Conductance on the Magnetic-layer Thickness in Magnetic Tunnel Junctions

The dependence of the conductance on the ferromagnetic (FM) layer thickness in magnetic tunnel junctions is investigated theoretically, and an analytical equation is derived with the reflection and transmission amplitudes of the separated interfaces. The conductance oscillates as the FM layer thickness increases, and the oscillation period is determined from the Fermi surface of the FM layer. Numerical calculations are carried out, and the analytical model is in a good agreement with the exact result. The experimental results of the Fe/MgO/Fe/Cr tunnel junctions are explained with the analytical model.