Effects of the surface and interface on the magneto-optical properties in (Co, Ni)/Cu(001) ultrathin films

The thickness dependence of the magneto-optical properties has been investigated for epitaxially grown face-centered-cubic Co and Ni films on a Cu(001) surface. An energy shift toward the low-energy side in the high-energy structure of the off-diagonal conductivity spectra of 20 Angstrom thick films is found for both the Co and Ni films. Non-self-consistent band calculations for the fee form of Co and Ni are carried out with changing lattice parameter. The calculated conductivity spectra are compared with the experimental results. The energy shift is attributed to the narrowing of the 3d band which might be due to the expansion of the atomic volume due to the lattice mismatch in the interface and the reduction of the atomic coordination number in the surface and in the interface.