Published online by Cambridge University Press: 25 February 2011
A large softening of the shear modulus has been reported in metallic superlattices composed of insoluble bcc/fcc metals. In an attempt to understand this elastic anomaly, we have studied the microstructure of Fe/Cu bilayers as a function of the Fe thickness with transmission electron microscopy (TEM). Analysis of the moire fringes observed in plan-view TEM images revealed that the fee Fe structure epitaxially grows on the (001) Cu up to a thickness of 2.0 nm. At 2.3 nm, the bec Fe structure nucleates, accompanying lattice rotation around the growth direction with respect to the underlying fee structure. As the Fe thickness further increases, submicron polycrystalline grains formed. Based on these results, the microstructure of the metallic superlattices and its relation to the softening of the shear modulus will be discussed.