Abstract
The magnetic behaviour of ferromagnetic/non-ferromagnetic/ferromagnetic trilayers is strongly dependent on the nature of the interface between layers, the strain in the layers and the extent of any interdiffusion or reaction between layers and substrate. In this paper, results are presented from a polarization-dependent in situ XAFS study of Fe/Pd/Fe trilayers epitaxially grown on GaAs(001)-(4×6). Fe and Pd K-edge spectra were obtained both above and below the critical angle for total reflection. The structure of iron grown on the Ga-terminated 4×6 reconstructed surface of the GaAs(001) substrate, for thicknesses greater than 6 monolayers, is tetragonally distorted from its natural bcc structure with contracted and expanded lattice constants in the in-plane and out-of-plane directions, respectively. The intermediate Pd layer shows distortion from its natural fcc structure. Alloying at the interface with the underlying Fe is restricted to a depth of 0.5–1.0 monolayers (ML). The upper layer of Fe shows tetragonal distortion similar to the layers of Fe grown on GaAs(001)-4×6. However, the upper distortion is stronger. There is also evidence of alloy formation at the interface involving the underlying Pd with the thickness of the alloy region being 2–2.5 ML.
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