Orbital Magnetism and Magnetic Anisotropy Probed with Ferromagnetic Resonance

Abstract

Via ferromagnetic resonance both the magnetic anisotropy energy (MAE) and the spectroscopic splitting tensor ( $g$ tensor) for a bcc ${\mathrm{Fe}}_{2}/{\mathrm{V}}_{5}(001)$ superlattice are measured independently. The theoretically proposed proportionality between the anisotropy of the orbital moment ${\ensuremath{\mu}}_{L}$ and the MAE is quantitatively checked and its limitations are discussed. From layer-resolved first-principles calculations we find a reduced spin moment ${\ensuremath{\mu}}_{S}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.62{\ensuremath{\mu}}_{B}$ for Fe and ${\ensuremath{\mu}}_{S}^{\mathrm{V}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.67{\ensuremath{\mu}}_{B}$ in the first V layer. The $g$-tensor elements reveal a $300%$ enhanced ratio ${\ensuremath{\mu}}_{L}/{\ensuremath{\mu}}_{S}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.133$ in comparison to bulk Fe. The MAE and the orbital moment anisotropy is found to be unusually small for Fe monolayers.