Crystal-axis dependence of nonreciprocal spin-wave transmission in asymmetric Fe/MgO/NiFe trilayers

Abstract We investigated the crystal-axis dependence of nonreciprocal spin-wave transmission in asymmetric Fe/MgO/NiFe trilayer waveguides. Spin-wave transmission was measured in the Damon–Eshbach geometry for two configurations: the easy-axis configuration, with the magnetic field applied along Fe[100], and the hard-axis configuration, with the field along Fe[110]. The transmission spectra exhibited propagation-direction-dependent differences in both amplitude and frequency. In particular, the directional amplitude difference of one experimentally observed branch reversed its polarity upon reversal of the external magnetic field in both configurations. Micromagnetic simulations showed propagation-direction-dependent localization of the dynamic magnetization and revealed that the spectral separation between the Fe-like and NiFe-like branches depended on the orientation relative to the Fe crystal axes. These results demonstrate the important role of the Fe crystal axes in nonreciprocal spin-wave transmission in asymmetric magnetic multilayers.