Magnetoresistance Associated with Antiferromagnetic Interlayer Coupling Spaced by a Semiconductor in Fe/Si Multilayers

Multilayer Fe/Si films with constant Fe thickness (2.6 nm) and variable Si thickness are investigated. Negative magnetoresistance is observed and two different temperature dependences are found as a function of Si thickness. For $t_{\mathrm{Si}}=1.2\mathrm{}$ nm, the magnetoresistance decreases with temperature decrease. For $t_{\mathrm{Si}}>1.5\mathrm{}$ nm, the magnetoresistance increases (weakly) with temperature decrease. The magnetoresistance is attributed to spin-dependent scattering caused by antiferromagnetic layer coupling across a semiconducting spacer: narrow gap iron silicide for thin Si spacer layers and amorphous Si for thicker spacer layers.