Exchange interaction in Co/Bi/Co thin-film systems with Bi interlayer

The magneto-optical and magnetic properties of Co(5 nm)/Bi/Co(5 nm) samples and the peculiarities of exchange coupling between Co layers through the Bi spacer layer are studied. The magneto-optical investigations indicate that the shapes of Transverse Kerr effect (TKE) spectra are similar for all studied samples but the TKE values decrease at tBi >4 nm as compared with TKE values of the single-layer Co thin film. The decrease in the volume ratio of the magnetic to nonmagnetic phases causes the reduction of the contribution of the magnetic phase to magnetooptical signals. Magnetic investigations show that the coercivity force, HC, and saturation field, HS, of the Co/Bi/Co samples increase with increasing tBi. The oscillatory behavior of HC and HS with various periods (short and long) is observed in a wide range of tBi values (from 0.2 to 50 nm). These data are explained by the dependence of Fermi energy on tBi and the changes in the Bi band structure with decreasing tBi.