Structurally Tunable Ferromagnetic Resonance in Artificial Magnonic Crystals of Medium‐Entropy Alloys

ABSTRACT The high‐frequency characteristics of magnetic thin films exhibit promising application prospects in the field of Power System‐on‐Chip (PwrSoC). Compared with traditional Permalloy films, medium‐entropy FeCoNi alloy films exhibit significant advantages in high‐frequency performance, attributed to their higher saturation magnetization and lower magnetic loss. However, the intrinsic correlation between the magnetic structures and macroscopic properties remains unclear since there is no clear evolution between the two. Therefore, clarifying the nature of the relationship between the magnetic structural properties and their macroscopic properties is of great significance for promoting their practical application in the PwrSoC field. In this study, magnonic crystals were fabricated via micro/nano‐manufacturing technology, aiming to achieve reconfigurable Ferromagnetic Resonance (FMR) of medium‐entropy alloy. Systematic observation of the magnetic structure evolution process was conducted using in situ Lorentz Transmission Electron Microscopy (LZ‐TEM), revealing the phenomenon of FMR splitting induced by ordered domain wall arrangement under different magnetic fields. Precise regulation of the magnetic domain resonance frequency and modes can be realized by tuning structural parameters and magnetic field strength. Micromagnetic simulation results further verify the correlation between magnetic structures and domain resonance modes. This finding provides a foundation for the future design of magnetic thin film micro‐inductors in high‐frequency PwrSoC applications.