Spin wave dispersion in Permalloy antidot array with alternating holes diameter

The dispersion of spin waves in a Permalloy binary antidot array constituted by two alternated antidot sublattices with different diameters of the circular holes has been investigated. The diameters of the holes are nm and nm with a holes center-to-center spacing of 425 nm. The spin wave frequency has been measured with Brillouin light scattering applying a magnetic field along the edge of the square unit cell of the lattice and sweeping the spin-wave wave vector along the perpendicular direction. The measured dispersion has been compared with calculations performed by the plane wave method, achieving a good agreement with the experimental results over the whole wave vector range.