AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Wednesday Sessions
       Session MI+TF-WeA

Paper MI+TF-WeA3
On the Magnetic Properties of Ultra Thin Epitaxial Fe Films on GaAs(001)

Wednesday, November 5, 2003, 2:40 pm, Room 316

Session: Magnetic Thin Films
Presenter: G.D. Waddill, University of Missouri, Rolla
Authors: S.A. Morton, Lawrence Livermore National Laboratory
J.R. Neal, University of Salford, UK
M. Spangenberg, University of Salford, UK
T.-H. Shen, University of Salford, UK
A.E.R. Malins, CLRC Daresbury Laboratory, UK
E.A. Seddon, CLRC Daresbury Laboratory, UK
D. Greig, University of Leeds, UK
J.A.D. Matthew, University of York, UK
G.D. Waddill, University of Missouri, Rolla
J.G. Tobin, Lawrence Livermore National Laboratory
Correspondent: Click to Email
The magnetic properties of epitaxial Fe films on GaAs have attracted considerable interest in recent years because of their potential for use as spin injection sources for spintronic devices; however, previous studies have been unable to demonstrate a magnetic signature in films with thicknesses below approximately 5 ML. A number of possible explanations for this observation have been proposed such as the presence of a magnetically dead interfacial layer of Fe2As. However, by measuring the thickness and temperature dependence of the Fe 3p core level magnetic linear dichroism signal we have shown that such films are indeed ferromagnetic but that their Curie temperature is substantially below room temperature. For instance a Tc of approximately 240K was measured for thin films with a nominal thickness of 0.9 nm. Furthermore the values of the Curie temperature in this thickness regime have been shown to be extremely sensitive both to initial substrate conditions and to the overall film thickness; an increase in the thickness of 0.35nm results in a Curie temperature above room temperature. These measurements have been complemented with spin resolved and angle resolved measurements of the Fe/GaAs valence band and core levels; together with ex-situ XRD and SPM studies of sample growth. The origins of the evolving magnetic behavior of Fe films on GaAs(001) from 1-50ML is discussed in terms of the spin dependent electronic band structure and the stoichiometry and growth morphology.