Surface-induced antiparallel coupling at the surface of a B2-ordered FeCr alloy

Abstract Using a self-consistent tight-binding real-space model within the unrestricted Hartree-Fock approximation to the Hubbard Hamiltonian, we have investigated local polarisation at the low Miller-index surfaces of an FeCr (B2) alloy. In all cases, i.e. (001), (110) and (111), the local polarisation at the surface is found to be antiferromagnetically coupled with the subsurface layer, in contrast to the parallel coupling between Fe and Cr in bulk FeCr. This spin-flip configuration is directly related to surface effects, and means that the differences between recent in-situ magnetometer measurements and energy-resolved spin-polarised secondary-electron emission could be due to alloy formation at the FeCr interface.