Orbital Magnetism and Magnetic Anisotropy Probed with Ferromagnetic Resonance

Via ferromagnetic resonance both the magnetic anisotropy energy (MAE) and the spectroscopic splitting tensor ( $g$ tensor) for a bcc ${\mathrm{Fe}}_2/{\mathrm{V}}_5\left(001\right)$ superlattice are measured independently. The theoretically proposed proportionality between the anisotropy of the orbital moment ${\mu }_L$ and the MAE is quantitatively checked and its limitations are discussed. From layer-resolved first-principles calculations we find a reduced spin moment ${\mu }_S=1.62\mathrm{}{\mu }_B$ for Fe and ${\mu }_S^{\mathrm{V}}=-0.67\mathrm{}{\mu }_B$ in the first V layer. The $g$-tensor elements reveal a $300\%$ enhanced ratio ${\mu }_L/{\mu }_S=0.133\mathrm{}$ in comparison to bulk Fe. The MAE and the orbital moment anisotropy is found to be unusually small for Fe monolayers.