Non-reciprocity of dipole-exchange spin waves in thin ferromagnetic films

The non-reciprocity and asymmetry of the modal profiles for dipole-exchange spin waves have been investigated theoretically. We were interested in the most important case for applications: the waves propagating in in-plane magnetized ferromagnetic films at a right angle to the applied magnetic field. For large-magnetic moment ferromagnetic metallic films with typical thicknesses 10-60 nm which are largely considered promising for magnonic and spintronic applications, the contribution of exchange energy to the total magnetic energy is important; however, their dynamics is most often treated using the exchange-free Damon-Eschbach approach. In this work, we show that although this approach is valid for treatment of wave dispersion, it fails to properly describe such fundamental property of wave excitations as wave modal profiles. Namely we show that the fundamental mode of the dipole-exchange spectrum is localized at the film surface opposite to the surface of localization of the exchange-free Damon-Eshbach surface wave. This "anomalous" localization of the wave does not affect the non-reciprocity of spin wave excitation by microstrip and coplanar transducers but may be detected in other types of experiments. © 2013 American Institute of Physics.