Influence of structural changes in a periodic antidot waveguide on the spin-wave spectra

Abstract

We demonstrate that the magnonic band structure including the band gap of ferromagnetic antidot waveguide can be significantly tuned by a relatively weak modulation of its structural parameters. We study the magnonic band structure in nanoscale spin wave waveguides with the periodically distributed small antidots along its central line by two independent computational methods, namely the micromagnetic simulation and plane wave method. The calculations were performed with consideration of both the exchange and dipolar interactions. For the exchange dominated regime we discuss, in details, the impact of the changes of the lattice constant, size and shape of the antidots on the spin wave spectra. We have shown that precise choice of these parameters is crucial for achieving desired properties of antidot waveguides, i.e., a large group velocity and filtering properties due to existence of magnonic band gaps. We discuss different mechanisms of magnonic gap opening resulting from Bragg scattering or anti-crossing of modes. We have shown, that the dipolar interactions start to assert their role in the spin wave spectrum when the waveguide is scaled up, but even for a period of few hundreds of nanomaters the magnonic band structure preserve qualitatively the properties found in the exchange dominating regime. The obtained results are important for future development of magnonic crystal based devices.