Spin wave modes in ferromagnetic tubes

Abstract

Resonances are observed in the transmission between two coplanar waveguides coupled by ferromagnetic Co90Ta5Zr5 tubes that wrap around their shorted ends. The resonances are assigned to the magnetostatic surface waves that counter propagate along the tube perimeter. We use a model based on an infinite ferromagnetic tube, with elliptical cross section of roughly the same dimensions as the studied structure. Additional theoretical analysis of the fundamental precession mode observed in experiment is carried out. Periodic boundary conditions dictated by the tube perimeter and applied to magnetostatic surface waves quantitatively account for the experimentally observed bandwidth of excited modes, despite the contorted tubular shape. The tubular topology appears to be more important than the shape details.