Observation of a low Curie temperature ferromagnetic phase of ultrathin epitaxial Fe films on GaAs(0 0 1)

• Published in: Journal of magnetism and magnetic materials 2005-04, Vol.292, p.241-247
• Main Authors: Spangenberg, M., Neal, J.R., Shen, T.-H., Morton, S.A., Tobin, J.G., Waddill, G.D., Matthew, J.A.D., Greig, D., Malins, A.E.R., Seddon, E.A., Hopkinson, M.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Core level photoelectrons; Curie temperature; Diamagnetism, paramagnetism and superparamagnetism; Epitaxial Fe/GaAs; Exact sciences and technology; Magnetic linear dichroism; Magnetic properties and materials; Magnetic properties of monolayers and thin films; Magnetic properties of surface, thin films and multilayers; Physics; Ultra thin magnetic films
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2004.10.117

The magnetic properties of epitaxial Fe films on GaAs in the range of the first few monolayers have been the subject of a considerable number of investigations in recent years. The absence of magnetic signatures at room temperature has been attributed to the existence of a magnetic ‘dead’ layer as well as superparamagnetism. By examining the temperature dependence of the magnetic linear dichroism of the Fe core level photoelectrons, we found a ferromagnetic regime with a Curie temperature, T c substantially lower than room temperature, e.g., a T c of about 240 K for thin films of a nominal thickness of 0.9 nm. The values of Curie temperature were sensitive to the initial GaAs substrate conditions and the thickness of the Fe over-layer with a layer of thickness of 1.25 nm showing a T c above room temperature. The data suggest that the thin Fe films on GaAs(0 0 1) may have ferromagnetic character at an earlier stage of growth than previously expected, although a weaker exchange interaction in the films leads to a substantial reduction in Curie temperature.