Study of the barrier height in exchange coupled Fe/Fe_1-xSi_x(x>0.70) multilayers

Fe/Fe_1-xSi_x multilayers show distinct antiferromagnetic (AF) coupling for a wide spacer composition range 0.50<x≤1.00. As the Si content x increases, the spacer changes from metallic to insulating and the AF coupling strength (J) is significantly enhanced from 0.05 to 1.20 erg/cm². We have explained the temperature dependence of the coupling constants J₁ and J₂ in terms of the quantum interference model by taking an unknown energy difference Δ(=U-ε_F) as a fitting parameter, where ε_F is the Fermi level of Fe and U is the potential of the Fe_1-xSi_x. The aim of the present work is to determine the quantity Δ experimentally for the insulating composition range of x>0.70. The quantity Δ was evaluated both from I-V characteristics and the temperature dependence of the resistivity with the current perpendicular to the sample plane using a crossed electrode geometry junction. It is found that the barrier height increases from 0.15 to 0.70 eV with increasing the Si content x. These values almost agree with the parameter Δ deduced from the temperature dependence of J₁ and J₂. This agreement supports the validity of our previous calculations based on the quantum interference model.