Magnetic Splitting of Valence States in Ferromagnetic and Antiferromagnetic Lanthanide Metals

The magnetic splitting of ${\Delta }_2$ valence states in the heavy lanthanide metals Gd, Tb, Dy, and Ho was studied in epitaxial films by angle-resolved photoemission, revealing an essentially Stoner-like temperature dependence in all cases. It scales linearly with the $4f$ spin moment, even in the case of the helical antiferromagnet Ho. Such a behavior can be explained by a substantial localization of the corresponding wave function in the $c$ direction. The helical magnetic structure was confirmed for the thin Ho films by in situ resonant magnetic x-ray diffraction.