Magnetic hysteresis of dynamic response of one-dimensional magnonic crystals consisting of homogenous and alternating width nanowires observed with broadband ferromagnetic resonance

We systematically probed the dynamic behavior of homogenous and alternating width (AW) Ni80Fe20 nanowire (NW) arrays using broadband ferromagnetic resonance (FMR) spectroscopy as a function of geometrical parameters such as wire width and interwire spacing. For homogenous width NWs, the FMR responses are markedly sensitive to wire widths and interwire spacing due to spatially varying demagnetizing field. The collective spin-wave mode profile for ferromagneticly and antiferromagneticly ordered ground state has been investigated by controlling the relative alignment of magnetization of neighboring NWs. We show that magnetic ground states of coupled AW NW arrays can be controlled by applying different magnetic field histories, and the collective spin-wave mode is very sensitive to the difference in the widths of wires constituting AW wire arrays. We have also mapped the ferromagnetic and antiferromagnetic ground states magnetic configurations using magnetic force microscopy. Our experimental results are in good agreements with a simple analytical theory we suggest for phenomenological description of the collective oscillations.