The mean specimen potentials across a series of short period coherent face centered ferromagnetic Fe-Cu multilayers, grown on (001) Cu by UHV DC magnetron getter sputtering, have been measured using Fresnel contrast analysis1 in the transmission electron microscope. Multilayers A, B and C nominally had 100 repeats of (Fe2/Cu15), (Fe4Cu13) and (Fe6/Cu9) in units of atomic layers, and saturation magnetizations at 0K of 1.7, 0.7 and 0.8μB/Fe atom, respectively. X-ray diffraction measurements showed that the average (002) spacing in each multilayer was much greater than conventional elasticity theory would predict from the bulk elastic constants of face centered Fe and Cu.

Energy-filtered through focal image series of each multilayer (examined in cross-section) were obtained at 397kV using a JEOL 4000FX microscope equipped with a Gatan imaging filter, and a 3.4mrad objective aperture. Fig.1 shows two of the images obtained from multilayer A. The intensity in selected regions of each such image was projected parallel to the layers, the specimen thicknesses (t) of the regions were measured and the contrast of the resulting one dimensional fringe profiles was compared with calculations in order to determine both the shapes and the magnitudes of the potential profiles across the Fe layers.