Thickness dependence and magnetocrystalline anisotropy of the x-ray transverse magneto-optical Kerr effect at the Co 2p edges of ultrathin Co films on W(110)

Transverse magneto-optical Kerr-effect (T-MOKE) measurements have been carried out in the vicinity of the Co 2p absorption edges on atomically smooth, ultrathin hcp Co(0001) films deposited on W(110). The investigated film thicknesses range from the submonolayer coverage up to 15 atomic monolayers. The reflectivity and T-MOKE spectra are compared to model calculations based on the Fresnel formalism, employing optical constants from independent x-ray magnetic circular dichroism (XMCD) experiments. Strong thickness dependent effects in both the p-polarized reflectivity and the T-MOKE are due to interference and could nicely be reproduced by our calculations. Moreover, an anisotropy in the T-MOKE response is observed for magnetizations along the [110] and [001] directions, caused by the uniaxial magnetic anisotropy in the Co films