Magnon signatures of multidimensional reconfigurations in multilayer square artificial spin ices

Abstract

We present an all-electrical, broadband spin-wave spectroscopy study of three-dimensional square artificial spin ices composed of dipolarly coupled ferromagnetic layers of varying thicknesses separated by a non-magnetic spacer. Our experiments, in the saturated regime, reveal that the spin-wave spectra exhibit a strong dependence on both the angle of the applied magnetic field and the geometrical aspect ratio of the ferromagnetic layers. Micromagnetic simulations and analytical calculations, utilizing the Smit–Beljers formalism, demonstrate good agreement with our experimental findings. In the magnetic switching regime, the spin-wave spectra indicate an antiparallel alignment between the two ferromagnetic layers. This configuration is highly sensitive to the field angle, suggesting the presence of multidimensional reconfigurations within the multilayer artificial spin ice. Furthermore, employing a minor loop field protocol, we show that the spin-wave modes associated with the antiparallel alignment remain reproducible, even after 100 minor loop cycles, providing intriguing possibilities for magnonic engineering.