Magneto-optical effects of ultrathin ferro-, antiferro- and non-magnetic films

Thickness dependence of the magneto-optical Kerr effects (MOKE) in ultrathin ferromagnetic films, antiferromagnetic films and nonmagnetic films were measured carefully employing wedge shaped samples at room temperature. The oscillations of the polar Kerr ellipticity with respect to the film thickness and its energy dependence were observed for the Fe and Au ultrathin films, and revealed a formation of spin-polarized quantum well states both in the bcc-Fe(100) layers and the fcc-Au(001) layers. On the other hand, bcc-Cr (100) ultrathin layers grown on 3ML of Fe(100) layer showed about 2ML period oscillation of the polar MOKE for the photon energy in between 2.25 and 3.75eV, indicating an existence of a long range antiferromagnetic order. The Cr film also showed energy dependent oscillation peaks for the very thin region (d<10ML). The longitudinal MOKE were measured also for Cr samples, and revealed 2ML period oscillation. The mechanism of the MOKE oscillations is discussed from the view points of quantum size effects and the antiferromagnetic order.