Magnetic response of aperiodic wire networks based on Fibonacci distortions of square antidot lattices

The static and dynamic magnetic responses of patterned ferromagnetic thin films are uniquely altered in the case of aperiodic patterns that retain long-range order (e.g., quasicrystals). We have fabricated permalloy wire networks based on periodic square antidot lattices (ADLs) distorted according to an aperiodic Fibonacci sequence applied to two lattice translations, d₁=1618nm and d₂=1000nm. The wire segment thickness is fixed at t=25nm, and the width W varies from 80 to 510nm. We measured the DC magnetization between room temperature and 5K. Room-temperature, narrow-band (9.7GHz) ferromagnetic resonance (FMR) spectra were acquired for various directions of applied magnetic field. The DC magnetization curves exhibited pronounced step anomalies and plateaus that signal flux closure states. Although the Fibonacci distortion breaks the fourfold symmetry of a finite periodic square ADL, the FMR data exhibit fourfold rotational symmetry with respect to the applied DC magnetic field direction.