Fe/Cr superlattices with individual layer thicknesses in the range 1-50 atomic layers have been prepared and the structure and magnetic properties studied. Evidence from x-ray and electrical resistivity analyses suggests a transition from coherent to incoherent interfaces that takes place at a modulation wavelength of about 12 A. The magnetic properties of Fe/Cr superlattices were studied using SQUID magnetometry and have been found to be considerably different from those of single layer thin films of similar total thickness. In particular, the coercive force is found to be enhanced by as much as a factor of 10 at low temperatures. Superlattices with other nonmagnetic separation layers (V, Mn, Ag) were studied to determine the effect of this material's properties (lattice parameter, crystal and magnetic structure) on the properties of the Fe layers. Little difference was seen, suggesting that the observed property changes are not due to the magnetic, electronic, or structural properties of the separation layer material. Analysis of sandwich structures with only one or two layers of Fe (10-100 A thick) illustrate that size effects and magnetic coupling between Fe layers are important.
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