Spin-dependent photoabsorption at theL-edges of ferromagnetic Gd and Tb metal

The spin-dependent absorption of circularly polarized x-rays is studied at theL-edges of ferromagnetic Gd and Tb metal. At theL1-edge a spin-dependent part of the absorption coefficient of 10−3–10−2 is observed. Strong resonance absorption known as “white line” occurs at theL2- andL3-absorption onset. Correlated with it one finds large spin-dependent absorption effects with amplitudes of a few percent. The spin-dependent absorption spectra reflect the profiles of the spin densities of the states populated in the absorption process. Thep-states show spin densities correlated with the first two flat bands above the Fermi level. The spin density of thed-like states is concentrated in the energy range of the white line. In Gd a splitting of ∼(0.5–0.6) eV of the unoccupied 5d spin up and spin down bands is indicated for both spin-orbit partners. In Tb a large dependence of the 5d spin density on the spin-orbit configuration is observed. The experimental results on the spin densities in Gd are compared with band structure calculations for the ferromagnetic ground-state. The theoretical and experimental spin density profiles agree well for thep-states but not for thed-states. The discrepancy concerning thed-states may be attributed to core-hole polarization effects in the absorption process

Distribution of magnetic moments in Co/Pt and Co/Pt/Ir/Pt multilayers detected by magnetic x-ray absorption

Measurements of the spin-dependent absorption have been performed at the L2,3 edges in Pt and Ir in the multilayered structures 4ÅCo+χÅPt (χ = 9, 16, 23, 30, 40) and 4ÅCo+11ÅPt+8ÅIr+11ÅPt. The samples were prepared by sputtering and evaporating, respectively, and show a large perpendicular anisotropy. The measured circular magnetic X-ray dichroism (CMXD) profiles indicate a significant spin polarization of the Pt and the Ir interlayer. The results show that the moments of the Pt interlayers as well as of the innermost Ir layers couple ferromagnetically to the Co layers. The experimental findings are compared with the magnetic moment distribution for sharp interfaces obtained from linear muffin tin orbital (LMTO) band structure calculations