  Cubic chiral magnets, such as Cu$_{2}$OSeO$_{3}$, exhibit a variety of
non-collinear spin textures, including a trigonal lattice of spin whirls,
so-called skyrmions. Using magnetic resonant elastic x-ray scattering (REXS) on
a crystalline Bragg peak and its magnetic satellites while exciting the sample
with magnetic fields at GHz frequencies, we probe the ferromagnetic resonance
modes of these spin textures by means of the scattered intensity. Most notably,
the three eigenmodes of the skyrmion lattice are detected with large
sensitivity. As this novel technique, which we label REXS-FMR, is carried out
at distinct positions in reciprocal space, it allows to distinguish
contributions originating from different magnetic states, providing information
on the precise character, weight and mode mixing as a prerequisite of tailored
excitations for applications.
