Dynamic pinning at a Py/Co interface measured using inductive magnetometry

TL;DR

This study investigates how eddy currents influence standing spin wave modes in thin magnetic films using broadband FMR and inductive magnetometry, revealing layer ordering effects and differences from cavity FMR measurements.

Contribution

It provides new insights into eddy current effects on spin wave excitation in thin films and compares different measurement techniques for their sensitivity.

Findings

Eddy currents significantly affect spin wave amplitudes in thin films.

Layer ordering impacts the ratio of standing spin wave modes.

Cavity FMR shows weaker standing spin wave amplitudes than inductive methods.

Abstract

Broadband FMR responses for metallic single-layer and bi-layer magnetic films with total thicknesses smaller than the microwave magnetic skin depth have been studied. Two different types of microwave transducers were used to excite and detect magnetization precession: a narrow coplanar waveguide and a wide microstrip line. Both transducers show efficient excitation of higher-order standing spin wave modes. The ratio of amplitudes of the first standing spin wave to the fundamental resonant mode is independent of frequency for single films. In contrast, we find a strong variation of the amplitudes with frequency for bi-layers and the ratio is strongly dependent on the ordering of layers with respect to a stripline transducer. Most importantly, cavity FMR measurements on the same samples show considerably weaker amplitudes for the standing spin waves. All experimental data are consistent with expected effects due to screening by eddy currents in films with thicknesses below the microwave magnetic skin depth. Finally, conditions for observing eddy current effects in different types of experiments are critically examined.