The magnetic order of Cr layers on Fe(001) is studied taking into acco
unt 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-bi
nding 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% fo
r 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 bet
ween 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 inte
rdiffused at the interface, the more important is the decrease of the
magnetization. We compare our results to the many experimental data av
ailable.