Magneto-Optical Spectra in Co/MgO, Ni/MgO, Co/Ag and Ni/Ag Multilayers

Abstract

We investigated magnetization and magneto-optical spectra in Co/MgO, Ni/MgO, Co/Ag and Ni/Ag multilayers. All samples were prepared by magnetron sputtering. Crystal structures were determined by a small or middle angle X-ray diffraction pattern. More than four superlattice peaks were observed in all multilayers including MgO layers. Sharp superlattice peaks were observed in all multilayers including Ag layers. Magnetization decreases with a smaller ferromagnetic layer thickness in both Ag and MgO systems at room temperature. The same tendency was observed at 5 K. However, the results in the magneto-optical spectra show a contrast between MgO systems and Ag systems. The shape of the off-diagonal element of the conductivity tensor (ωσ x y ) changes drastically with the ferromagnetic layer thickness in MgO systems. However, the shape of the tensor ωσ x y does not depend on the ferromagnetic layer thickness in Ag systems. This contrasting result reflects the difference of the effect of interfaces on electrons in the ferromagnetic layers between insulating MgO and metal Ag.