MO sensing of magnetization in ultrathin ferromagnetic films sandwiched between dielectrics

Abstract

Magneto-optical (MO) enhancement in structures consisting of ultrathin magnetic layer sandwiched between dielectric films on an absorbing substrate reflector is demonstrated in an AlN/Ni/AlN/Si system. The AlN(14 nm)/Ni( t Ni)/AlN(14 nm) sandwiches with Ni thicknesses t Ni = 0.4, 0.8, 1.2, 1.5, 3 and 6 nm were prepared by rf-sputtering using water-cooled Si(111) substrates. We report here the near-normal incidence MO polar Kerr rotation (PKR) and ellipticity (PKE) spectra in the photon energy range 1.5–5.2 eV in magnetic fields up to 1 T. PKR hysteresis loops indicated the presence of magnetic ordering for t Ni = 1.5 nm, whereas the magnetic measurements, due to lack of sensitivity, could confirm the ferromagnetic ordering only for t Ni = 3 nm. Because of the AlN layers enclosing the Ni layer, a strong MO enhancement occurs above 4 eV. The principal features of the spectra were found to be consistent with the simulation based on an electromagnetic wave model of the optical interactions in magnetic multilayers.