AVS 45th International Symposium
    Magnetic Interfaces and Nanostructures Technical Group Thursday Sessions
       Session MI-ThM

Paper MI-ThM11
Light Scattering Cross Section for Mode Crossing of Spin Waves in Magnetic Films

Thursday, November 5, 1998, 11:40 am, Room 324/325

Session: Magnetic Spectroscopies
Presenter: F. Nizzoli, University of Ferrara and INFM, Italy
Authors: F. Nizzoli, University of Ferrara and INFM, Italy
J.M.V. Ngaboyisonga, Makerere University, Uganda
L. Giovannini, University of Ferrara and INFM, Italy
Correspondent: Click to Email
The dispersion curves of spin waves in magnetic films show a typical behavior as a function of the surface wave vector, film thickness and in-plane propagation angle, i.e. mode repulsion between the surface mode and bulk modes. The purpose of this work is to study theoretically the Brillouin light scattering (BLS) intensity from spin waves versus the surface wave vector Q in case of mode repulsion in a magnetic film of thickness d, under the condition Qd nearly equal to 1. In such a case both dipole and exchange interactions are equally important and must be included. The calculations, for a 85 nm thick iron film, are performed within the macroscopic partial waves approach of Rado-Hicken and Cochran-Dutcher, based on the solution of the Landau-Lifshitz equation of motion of the magnetization with the proper boundary conditions. It is found that the BLS cross section shows an antiresonant behavior close to the gap between the modes. We have investigated the physical meaning of this behavior by analyzing the different contribution of the partial waves to the cross section . For Q below the gap three relevant partial waves interfere destructively, while the opposite occurs for a wave vector above the gap. The interference effects, responsible for the Fano-type antiresonant behavior of the total scattering intensity, are explained in terms of a sudden change of the dynamic magnetization across the film, when mode repulsion occurs. The effect of the magnetic anisotropy on the antiresonant behavior of the BLS cross section is also investigated.