Interfacial alloying and interfacial coupling in Cr/Fe(001)

The magnetic order of Cr layers on Fe(001) is studied taking into account interfacial alloying and possible interdiffusion. The interfacial alloy is modeled by either a one-monolayer or a two-monolayer ordered compound whose concentration is varied. The spin-polarized electronic structure is determined self-consistently by solving a $d$-band tight-binding Hamiltonian. We determine the concentration for which the phase of the layer-by-layer antiferromagnetic structure of Cr changes in the Cr film on Fe(001). We find that in the case of two interfacial mixed layers, a $\pi$ phase shift occurs at a Cr concentration between 33% and 50% when three monolayers (ML) of Cr are deposited. The occurrence of this $\pi$ phase shift changes to a concentration between 11% and 25% for a more important coverage of Cr (namely 11 ML). When only one mixed layer is considered, the phase of the antiferromagnetic stacking of Cr changes at a concentration between 25% and 33% for 3 ML of Cr and between 33% and 50% for 11 ML of Cr. A simulation of the variation of the magnetization during Cr growth shows that the more Cr and Fe are interdiffused at the interface, the more important is the decrease of the magnetization. We compare our results to the many experimental data available.