This paper reports on the results of ab initio calculations of the electronic and magnetic properties of Si digital heterostructures doped with a Fe monolayer of the substitutional or interstitial type. It has been revealed that, after the structural relaxation, heterostructures of both types exhibit a two-dimensional metallic behavior and a ferromagnetic ordering in the range of Si spacer thicknesses up to 19 atomic layers. The magnetization and spin polarization at the Fermi level for the heterostructures with an Fe monolayer of the substitutional type are two times higher than those for the system with an Fe monolayer of the interstitial type.

This study was supported in part by the University of the Basque Country (project GV-UPV, grant no. IT-366-07) and the Spanish Ministerio de Ciencia y Tecnología (MCyT) (grant no. FIS2007-06671- C02-01).

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