Room-temperature magnetic phases of Fe on fcc Co(001) and Ni(001)

A sequence of three distinct magnetic phases of Fe are found for growth on both fee Co(001) and Ni(001) using x-ray magnetic circular dichroism. For Fe coverages below 5 ML the films are ferromagnetic, with the magnetic moments aligned perpendicular to the surface for growth on Ni and parallel to the surface for growth on Co. Between 5 and 11 ML the Fe films are nonmagnetic at room temperature, but include a ferromagnetic live monolayer at the Fe/Co and Fe/Ni interface. The moment of the magnetically live monolayer is aligned perpendicular to the surface for growth on Ni and parallel to the surface for growth on Co. Above 11 ML the Fe films are once again ferromagnetic. An identical sequence of magnetic phase transitions is known to occur for Fe growth on Cu(001). Based on this comparison and on the nearly identical lateral lattice constants of fee Co, Ni, and Cu, we conclude that Fe growth on fee Co(001) and Ni(001) follows the same sequence of crystalline phase transitions as Fe growth on Cu(001). Supporting this conclusion are the identical sequence of surface reconstructions observed by low-energy electron diffraction for Fe growth on Co(001) and Cu(001). For Fe/Ni(001) these surface structural changes are not observed, suggesting that details in the growth mode of Fe on Ni are different for Fe on Co and Cu.