Magneto-optical anisotropy study of Fe-n/Au-n superlattices

Extended experimental and theoretical study of the observed large magneto-o ptical anisotropy (MOA) is presented for a series of Fe-n/Au-n superlattice s prepared by molecular beam epitaxy with n=1,2,3 of Fe and An atomic plane s of (001) orientation. The anisotropy of the off-diagonal component of the optical conductivity tensor with respect to the change of the magnetizatio n direction is determined in the photon energy range 0.8-5.8 eV from the me asurements of the magneto-optical polar and longitudinal saturated complex Kerr angles and the optical data measured by the spectroscopic ellipsometry . The magnitude of the observed anisotropy, decreasing with the increase of n, and its energy dependence are well reproduced by the band structure cal culations performed within the local spin-density approximation to the dens ity functional theory. The results of the calculations show that the micros copic origin of the large MOA is the interplay of the strong spin-orbit cou pling on Au sites and the large exchange splitting on Fe sites via Au d-Fe d hybridization of the electronic states at the interfaces. The high sensit ivity of the MOA to the interface structure is studied by ab initio modelin g of the effects of substitutional disorder and the roughness at the interf aces. It is shown that a good agreement with the experiment is obtained whe n the interface roughness effect is taken into account. The orientation ani sotropy of the d orbital moment is calculated from the first principles and analyzed on the basis of d orbital symmetry consideration. The relationshi p between the orbital moment anisotropy and the MOA is discussed.