Permalloy (NiFe) nanometer square-antidot arrays: Dynamic modes and use as a monolithic microwave band-pass filter

Nanometer sized Permalloy antidot arrays with different square hole sizes have been fabricated using field emission scanning electron microscopy technique. The dynamic properties of the antidot arrays are measured at GHz frequencies using a Vector Network Analyzer. For a given applied magnetic field, we observe three resonance frequencies - one corresponds to that of a uniform mode in an infinitely extended film, and the other two (above and below this mode in frequency) correspond to modes associated with finite structures. These two modes exhibit an effective uniaxial in-plane anisotropy. The static behavior of the antidot arrays are simulated using a micromagnetic model and the electromagnetic signal transmission is analyzed using an analytical model. The results show that the three different resonance frequencies are due to the different localized shape anisotropies created by the nonmagnetic holes in the antidot array. Possible application as a magnetically tunable local band-pass filter at 5G frequency band is also studied.