Magnetic anisotropy energy and the anisotropy of the orbital moment of Ni in Ni/Pt multilayers

Angular-dependent x-ray magnetic circular dichroism experiments are perform ed on Ni/Pt multilayers at the Ni L-2,L-3 edges under magnetic fields up to 50 kG at a temperature of 10 K. By rotating the applied field away from th e easy axis a decrease of the ratio of the orbital-to-spin magnetic moment mu(L)/ mu(S) Of Ni is observed for perpendicularly magnetized Ni/Pt layers which show considerable magnetic anisotropy energy (approximate to 20 mu eV /atom). Saturation effects in the recorded spectra, depending on both the t hicknesses of Ni and Pt, are shown to lead into erroneous conclusions in th e determination of mu(L)/mu(S) and they have to be considered in the analys is. An anisotropy of the Ni-orbital moment Delta mu(L) as large as 22% of m u(L) is determined. Delta mu(L) is demonstrated to be the origin of the mag netic anisotropy energy of 3d ferromagnetic elements.