Metal-semiconductor multilayers (Mls) are extensively studied because of their potential application in electronics. The main goal of our study was to examine whether the existence of the antiferromagnetic (AF) exchange coupling in Fe/Si_xFe_1-x (x=1, 0.66, 0.5) Mls is related to the appearance of the interfacial Fe silicides. The examined Mls were deposited in UHV by magnetron sputtering onto oxidized Si wafers for different Fe layer thicknesses 0.3<d_Fe<4nm. The crystalline structure of our samples and their multilayer periodicity were examined using the high- and small-angle X-ray diffraction, supplemented with the transmission electron microscopy of the cross-section. We shoved that both magnetic and electronic properties of the AF coupled Fe/Si Mls are influenced by interfacial mixing between Fe and Si layers. The current-voltage (I-V) characteristics measured at room temperature, perpendicularly to the Ml planes allowed us to show the semiconducting character of nominally pure Si, Si_0.5Fe_0.5 and Si_0.66Fe_0.33 spacer layers. The tunnelling barrier height estimated for Fe(3nm)/Si(1.1nm) Mls was found to be 1eV. We showed that the application of interfacial Co (or Au) thin layers prevent the Fe(Si) interdiffusion into Si(Fe) layers leading to the absence of AF coupling.

In order to find out the influence of Ge on AF coupling in Fe/Si Mls, Si was partially substituted by Ge in the spacer layer. Magnetization measurements of the [Fe(3nm)/Ge(d_Ge)]₁₅ Mls revealed no AF coupling up to d_Ge=3 nm, in contrast to Fe/Si system [1]. We found that addition of at least 0.5 nm of Ge, introduced either at the Fe/Si interface or in the center of Si spacer destroys the AF coupling.

[1] T. Luciński, M. Kopcewicz, A. Hütten, H. Brückl, S. Heitmann, T. Hempel, G. Reiss, J. Appl. Phys. 93 6501(2003).

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