AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThA

Paper MI-ThA8
"Acoustical" and "Optical" Spin Modes of a Fe/Cr/Fe/Cr/Fe Multilayer with Ferro- and Anti-ferromagnetic Couplings

Thursday, October 5, 2000, 4:20 pm, Room 206

Session: Magnetic Devices: GMR & Tunneling
Presenter: F. Nizzoli, University of Ferrara and INFM, Italy
Authors: F. Nizzoli, University of Ferrara and INFM, Italy
L. Giovannini, University of Ferrara and INFM, Italy
P. Vavassori, University of Ferrara and INFM, Italy
R. Zivieri, University of Ferrara and INFM, Italy
Correspondent: Click to Email
A study of the in-phase ("acoustical") and of the out-of phase ("optical") spin modes in layered ferromagnetic structures with both ferromagnetic and antiferromagnetic coupling is presented, in particular for the system Fe(20Å)/Cr(20Å)/Fe(20Å)/Cr(9Å)/Fe(100Å), for which experimental Brillouin scattering data are available@footnote 1@ In our model we take magnetocrystalline, uniaxial and shape anisotropies, Zeeman interaction, bilinear and biquadratic exchange interlayer couplings into account. The magnetization equilibrium configuration is calculated as a function of the external field using the steepest descent technique. A calculation of the dynamic magnetization assumed constant in each film gives an explanation of the behavior of the two kinds of modes at different magnetic fields applied along the easy axis. The "acoustical" mode is the lowest frequency one at low applied fields, but frequency exchanges with the "optical" modes occur at higher fields. It is found that the competition between the Zeeman and the biquadratic exchange terms is responsible for the appearance of a soft mode at a critical field marking a second-order phase transition.