ANTIFERROMAGNETIC VERSUS FERROMAGNETIC COUPLING IN FE CR(107) AND CR/FE(107)/

We have calculated the local magnetic moments and magnetic order for a Fe(Cr) monolayer adsorbed on a stepped Cr(Fe)(107) substrate. The ele ctronic structure at T=0 K has been self-consistently determined withi n the unrestricted Hartree-Fock approximation of the Hubbard Hamiltoni an in the framework of a real-space tight-binding method. In the Cr/Fe (107) system, two magnetic arrangements have been obtained, the more s table being the less frustrated as obtained in the case of V overlayer s on vicinal substrates of Fe. An analysis of both solutions in terms of the total energy calculation and the different degree of frustratio n is presented. For Fe/Cr(107), a two-step periodicity is obtained. Th e sign of the magnetization at the Fe overlayer changes from step to s tep. This spin-flop transition is consistent with the two-layer period oscillation recently observed in Fe/Cr/Fe wedge structures, and with the total magnetization determined from in situ magnetometer measureme nts during growth of ultrathin Fe films on Cr(001).