Structural, electronic, and magnetic properties of Au/Cr/Au(001) sandwiches: Theoretical total-energy studies

All-electron total-energy local-density studies of the structural, electronic, and magnetic properties of ordered Au/Cr/Au(001) sandwiches were undertaken to understand the report of superconductivity and the induced structural modification of Cr(001) by Au overlayers by Brodsky et al. These self-consistent spin-polarized calculations were carried out using the all-electron full-potential linearized-augmented-plane-wave method. Predicted structural properties, magnetic properties, charge and spin densities, contact hyperfine fields, and single-particle spectra are presented and discussed. The Cr lattice is found to be the same as in its bulk bcc environment. The Au-Cr interlayer spacing is expanded by about 3% with respect to the average of the bulk Au fcc and Cr bcc spacings; this expansion is mostly due to the formation of magnetic order at the interface. An enhancement of the Cr magnetic moment at the interface (to 1.55B) is predicted, which while 0.94B less than that found for the surface layer in Cr(001), indicates the persistence of Cr surface states near EF at the interface with the Au overlayers. These surface states, however, become more delocalized by their hybridization with the low-lying Au d band. Both the bcc structure of Cr layers and the magnetic character of the interface Cr states argue against models proposed previously for the occurrence of superconductivity. We conclude that superconductivity is not a property for ordered Au/Cr/Au(001) sandwiches but that disorder may play some role.