Exchange splitting of epitaxial fcc Fe/Cu(100) versus bcc Fe/Ag(100)

The magnetic exchange splitting of epitaxial Fe films is determined using inverse photoemission. fcc Fe grown on Cu(100) is found in two phases, one obtained by deposition at 300 K with a splitting of 1.2 eV, and the second with a splitting of 0.9 eV obtained after annealing above 450 K. bcc Fe on Ag(100) exhibits a splitting of 1.8 eV, similar to that of bulk Fe. The magnetic splitting of the 3d states is shown to be correlated linearly with the local magnetic moment, with a slope of 1 eV/${\mathrm{\mu }}_{\mathit{B}}$. This relation holds not only for ferromagnets, but also for antiferromagnets, spin glasses, and the free atoms.