Magnetic circular dichroism at theKedge of nickel and iron

The spectra of the K-edge absorption and the magnetic circular dichroism (MCD) for ferromagnetic Ni and Fe are calculated on the basis of a tight-binding approximation including the spin-orbit interaction. The calculated spectra are in good agreement with the experiments and the previous band calculations near the photothreshold. It is shown that the spin-orbit interaction of the 3d states gives rise to a dominant contribution to the MCD while that of the 4p states plays only a minor role. This suggests that the MCD, which probes the orbital moment of p-symmetric (such as 4p) states on the core-hole site, is generated mainly by the 3d orbital moment on the neighboring sites through the p-d hybridization. The effect of the electric-quadrupole transition to the MCD of Ni is found at a close vicinity of the photothreshold. Sum rules for the dipole transition are discussed.