MAGNETO-OPTICAL SPECTRA OF ULTRATHIN Co FILMS SANDWICHED BETWEEN Pt LAYERS

Magneto-optical Kerr spectra have been measured for Pt(2 nm)/Co(0.2-2 nm)/Pt(60 nm) sandwich films, prepared by a molecular beam epitaxy technique onto MgO(111) substrates. From the reflection high energy diffraction observations, the Co layers on the Pt(111) base layers were confirmed to have a twinned fcc structure. The Kerr rotation of the sandwich films increased with increasing photon energy in a similar manner to those of Pt-Co alloys and multilayers, and as the Co layers become thicker, the magnitude of Kerr rotation becomes larger throughout the range of measurement (0.8∼4.1 eV). In order to characterize the magneto-optical properties of Pt/Co interfaces, the ωσ"xyspectrum of a Pt monolayer was estimated from the ωσ"xy of the sandwich by assuming that the Pt monolayer neighboring the Co layer are spinpolarized. The ωσ"xy for the Pt monolayer are considerably larger in magnitude than those of thick Co and Pt-Co sputtered alloy films in the high energy region. The experimental Kerr spectra with various Co thicknesses were reproduced by the simulation using ωσ"xy for the spin-polarized Pt.