In-Situ Observations of Magneto-Optical Spectra for Co/Cu (001) Ultrathin Films

The magneto-optical properties of ultrathin fcc Co films epitaxially grown on Cu (001) surfaces were investigated. The growth conditions were optimized, and the RHEED patterns of Co ultrathin films revealed streaks reflecting the symmetry of the fcc Cu (001) surface. Longitudinal Kerr hysteresis loops were square for Co coverage thicknesses greater than 6Ã…, and were detected down to 4Ã…. The longitudinal Kerr rotation and ellipticity spectra were measured over the photon energy range from 2.0 to 4.6 eV, after Co coverage deposition of each sample. The off-diagonal elements of the conductivity tensor (¿¿xy) were evaluated. When the Co coverage thickness is 50Ã…, the shapes of both the ¿¿\´xy and ¿¿"xy spectra showed essentially the same features as those of 1000Ã… thick fcc Co films. When the Co thickness decreased below 50Ã…, ¿¿"xy became smaller in magnitude. The decrease in ¿¿"xy as a fraction of a number of Co/Cu layers is discussed.