Observation of a Low Curie Temperature Ferromagnetic Phase of Ultrathin Epitaxial Fe Films on GaAs(0 0 1)
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, Tc substantially lower than room temperature, e.g., a Tc 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 Tc 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.
M. Spangenberg and J. R. Neal and T. H. Shen and S. A. Morton and J. G. Tobin and J. A. Matthew and D. Greig and A. E. Malins and E. A. Seddon and M. Hopkinson and G. D. Waddill, "Observation of a Low Curie Temperature Ferromagnetic Phase of Ultrathin Epitaxial Fe Films on GaAs(0 0 1)," Journal of Magnetism and Magnetic Materials, Elsevier, Apr 2005.
The definitive version is available at http://dx.doi.org/10.1016/j.jmmm.2004.10.117
Engineering and Physical Sciences Research Council
Lawrence Livermore National Laboratory
United States. Department of Energy
University of California (System)
Keywords and Phrases
Curie Temperature; Core Level Photoelectrons; Epitaxial Fe/GaAs; Magnetic Linear Dichroism; Ultra Thin Magnetic Films
Article - Conference proceedings
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