Spin waves in ultrathin multilayers with ferromagnetic and antiferromagnetic coupling: Fe/Cu and Fe/Cr -- Presentazione orale by R. Zivieri - Conferenza internazionale

We have studied the spin modes in ultrathin multilayers in presence of ferromagnetic and antiferromagnetic coupling. We have referred to epitaxial Cu(60Å)/Fe(20Å)/Cu/Fe(60Å)/Cu(60Å) heterostructures with the Cu spacer thickness ranging between 0 Å and 33 Å. The interlayer exchange coupling between Fe films obtained by Brillouin light scattering(BLS) from thermally excited spin waves is ferromagnetic for the whole range of Cu spacer thicknesses investigated. Using the magnetic parameters determined by the fit to the BLS data, we have carried out a detailed calculation of the BLS cross-section assuming the dynamic magnetization to be uniform across each magnetic film. A very good agreement between the calculated and the measured crosssections has been obtained. To analyze the effect of the antiferromagnetic exchange coupling on the spin modes we have considered the system Fe(20 Å)/Cr(20 Å)/Fe(20 Å)/Cr(9 Å)/Fe(100 Å) with both ferromagnetic and antiferromagnetic couplings studying the acoustical and optical spin modes. A calculation of the dynamic magnetization, assumed uniform in each film, gives an explanation of the behavior of the two kinds of modes at different magnetic fields. The acoustical mode is the lowest frequency one for low applied fields, but its frequency switches with that of the optical modes at higher fields. We have also found that the system exhibits soft modes as a function of the applied field. -- Presentazione orale by R. Zivieri - Conferenza internazionale