Brillouin light scattering from periodic multilayers composed of very thin magnetic films - art. no. 134406

摘要

A simple treatment of the dipole-dipole interaction between the magnetic films in a multilayer has been used to calculate the low-lying spin-wave modes in multilayer structures. It is assumed that in equilibrium the magnetization in each film is parallel to the applied magnetic field. It is also assumed that the magnetic films are thin enough so that the magnetization density remains uniform across the thickness of each film when the magnetization is thermally excited from equilibrium. Surface pinning energies and interlayer exchange coupling are included in the formalism. The calculated spin-wave modes have been used to investigate the scattered light spectrum in a Brillouin light scattering (BLS) experiment. The method has been applied to the cases of a surface mode on an infinite multilayer stack and to multilayers containing 5, 10, and 25 magnetic films having thicknesses up to 50 Angstrom and for nonmagnetic spacer layers having similar thicknesses. The scattered light spectra for such thin-film structures are very simple for multilayers having a total thickness less than, or comparable to, the optical decay length for light propagating through the multilayer structure. For such multilayers only those one or two modes give rise to an appreciable scattered light intensity for which the magnetization precessional amplitude varies very little from one magnetic film to the next. The frequencies corresponding to these strong BLS modes are insensitive to the interlayer exchange coupling because the magnetizations in neighboring films remain nearly parallel as they precess. [References: 24]