Magnetism of Co doped graphitic ZnO layers adsorbed on Si and Ag surfaces

Abstract

The effect of the substrate on Co doped graphitic ZnO layers adsorbed on metallic and semiconductor surfaces are investigated. The first principles results reveal that the magnetic interactions are strongly affected by the substrate. While graphitic layers of ZnO:Co on the well controlled metallic Ag(111) surface present weak ferromagnetic stability, on the semiconductor Si(111) surface they are strongly ferromagnetic coupled. The presence of metallic states in ZnO:Co adsorbed on Ag(111) surface favors a superexchange mechanism, weakening the ferromagnetic interaction. On the other hand, the magnetism of few layers of ZnO:Co on Si(111) surface is governed by a direct exchange mechanism, favoring a ferromagnetic coupling. This confined II–VI system doped with transition metal on a semiconductor surface presents higher magnetic stability than III–V nanostructures, and it is desired for nanostructured oxide/semiconductor room temperature ferromagnetism, using silicon technology.