MO POLAR KERR STUDIES OF CO RICH MOLECULAR-BEAM EPITAXY-GROWN AU CO MULTILAYERS/

Magneto-optical (MO) polar Kerr rotation and ellipticity (PKR and PKE, respectively) of Co rich Au(111)/Co(0001) multilayers grown by molecu lar beam epitaxy on GaAs(110) substrates are reported. The individual layer thicknesses, t(Au) and t(Co) were t(Au)/t(Co) = 2.6/3.2, 1.0/1.5 , and 0.65/0.8 nm. The samples displayed perpendicular magnetic anisot ropy smaller than demagnetization energy. PKR and PKE were measured at photon energies between 1.5 and 5.2 eV. In the multilayer with t(Co) = 1.5 nm, PKR at 3.1 eV reached a value of -0.34-degrees, remarkably h igher than that reported on Au rich multilayers. The spectra were comp ared.with theory. A satisfactory agreement was obtained only for the s ample with the largest bilayer thickness, t(Au) + t(Co) =5.8 nm. This indicates that when t(Au) and t(Co) are reduced to a few atomic monola yers the role of interfaces is increased. The effects of strain, defec ts, and atomic mixing at Au-Co interfaces become more important. Both the magnetic and optical properties are modified.