Magnetic decoupling in sputtered Fe/Si superlattices and multilayers

Sputtered Fe/Si superlattices were grown to study the magnetic coupling between ferromagnetic Fe layers (30 Å thick) for Si spacer-layer thicknesses (tSi) between 10 and 40 Å. The material is ferromagnetical for tSi≤13 Å and antiferromagnetically coupled for 13 Å≤tSi≤17 Å. For tSi≥17 Å the Fe layers are uncoupled. X-ray analysis indicates that the system is well layered, but that the crystal structure remains coherent only for tSi≤17 Å. These results, along with our Mössbauer investigation, strongly suggest that the Si layer is crystalline for tSi≤17 Å, and is silicide in nature. For thicker spacers, Si becomes amorphous. We propose a model of the layering that is consistent with the known properties of Fe silicide.