Spin-wave calculations for multilayered structures

Results are presented on the calculations of spin-wave frequencies in ferromagnetic layers, double layers, and multilayered structures for small, nonzero wave vectors such as can be investigated by, e.g., Brillouin light scattering. The underlying continuum-type magnetostatic theory includes both dipolar and exchange contributions and fully takes into account magnetic surface and interface anisotropies as well as interlayer exchange coupling. For single magnetic layers the detailed influence of surface anisotropies on both film surfaces is studied. For magnetic double layers the interlayer exchange coupling mechanism is investigated. In the case of multilayers consisting of alternating magnetic and nonmagnetic layers, the crossing regime between dipolar and exchange modes shows a strong dependence of the gap width on the amount of interface anisotropy. For small layer thicknesses the interlayer exchange coupling shifts the spin-wave frequencies of all but the highest-frequency dipolar modes into the exchange-mode regime. In the case of all-magnetic multilayered structures, a new type of collective spin-wave excitations arising from coupled exchange modes is predicted.