Antiferromagnetic coupling in Fe/Si/Fe structures with Co ``dusting'' layers

Artificial antiferromagnetic (AF) tunnelling Si-based structures are attracting a special interest due to extremely strong AF coupling, which exceeds 5mJ/m$^{2}$, low resistance-area product and resonant-type tunnelling magnetoresistance (TMR) [1]. A promising way to regulate the spin polarization in TMR structures is to insert Co ``dusting'' layers at interfaces [2]. We present AF coupling in Fe/Co/Si/Co/Fe epitaxial structures with sub-monolayer --thick Co ``dusting'' layers at interfaces and different thicknesses of the Si spacer. We determined the strength of AF coupling from spin-wave frequencies and angular dependence of the resonance field of the ferromagnetic resonance, as well as MOKE hysteresis. We found the AF coupling near 0.1mJ/m$^{2}$ which decays with the spacer thickness and detectable for 2nm-thick Si spacers. The presented results can open an avenue for magnetotransport studies in AF-coupled structures using interface engineering. [1]. R.R. Gareev \textit{et al}, JMMM \textbf{240}, 235 (2002), R.R. Gareev \textit{et al}, APL \textbf{88}, 172105 (2006). [2]. Y. Wang, X.F. Han, and X.-G. Zhang, APL \textbf{93}, 172501 (2008).