Determination of the Exchange Coupling Strengths for Fe/Au/Fe

We measure, as a function of interlayer thickness, the magnitude of the bilinear exchange coupling in an Fe/Au/Fe trilayer, to investigate the existing order of magnitude discrepancy between theory and experiment. We use Fe whisker substrates, scanning electron microscopy polarization analysis, and reflection high-energy electron diffraction to monitor the sample's magnetic and physical structure, and confocal magneto-optical Kerr effect to determine the coupling. We determine the exchange coupling strengths of the individual oscillating terms. The total bilinear coupling strength is $-1.9\mathrm{}\pm 0.2\mathrm{mJ}/{\mathrm{m}}^2$, for a Au interlayer thickness of 4 monolayers, in substantial agreement with current theory.