  We propose an alternative micromagnetic approach to determine the spin wave
dispersion relations in magnonic structures. Characteristic of the method is
that a limited area of the system is continuously excited with a spatially
uniform oscillating field, tuned at a given frequency. After a transitory time,
the regime magnetization dynamics is collected and a spatial Fourier analysis
on it determines the frequency vs wave vector relation. Combining several
simulations in any predetermined range of frequencies, at any resolution, we
investigate the dispersion relations for different kinds of magnonic crystals:
a dot array, an antidot array, and a bicomponent film. Especially compared to
traditional pulse-excitation methods this technique has many advantages. First,
the excitation power is concentrated at a single frequency, allowing the
corresponding spin waves to propagate with very low attenuation, resulting in a
higher k-space resolution. Second, the model allows to include very large wave
vector components, necessary to describe the high-frequency response of
non-quantized spin waves in quasi-continuous systems. Finally, we address some
possible experimental opportunities with respect to excitation/detection
techniques over large distances and the observation of the odd/even symmetry of
spin waves using Brillouin light scattering.
