MAGNETIC PHASES OF ULTRATHIN FE FILMS ON FEE CO(001)

A sequence of three distinct magnetic phases of epitaxial ultrathin films of Fe grown on fee Co(100) surfaces have been identified using low-energy electron diffraction (LEED) and X-ray magnetic circular dichroism (XMCD). The magnetic phases are correlated with changes in film structure that produce different surface reconstructions, which are similar to those found for epitaxial Fe ultrathin films grown on Cu(100) substrates. The room temperature magnetic phase diagram has been determined using X-ray dichroism magnetometry. For Fe coverages below 5 ML the films crystallize in an fct phase and are ferromagnetic. Between 5 and 11 ML the Fe grows in an fee phase which is nonmagnetic at room temperature, but has a magnetic live monolayer at the Co/Fe interface. The magnetic and compositional interfaces do not coincide. Above 11 ML the Fe films grow in the ferromagnetic bcc phase.