  The resonant eigenmodes of a nitrogen-implanted iron {\alpha}'-FeN
characterized by weak stripe domains are investigated by Brillouin light
scattering and broadband ferromagnetic resonance experiments, assisted by
micromagnetic simulations. The spectrum of the dynamic eigenmodes in the
presence of the weak stripes is very rich and two different families of modes
can be selectively detected using different techniques or different
experimental configurations. Attention is paid to the evolution of the mode
frequencies and spatial profiles under the application of an external magnetic
field, of variable intensity, in the direction parallel or transverse to the
stripes. The different evolution of the modes with the external magnetic field
is accompanied by a distinctive spatial localization in specific regions, such
as the closure domains at the surface of the stripes and the bulk domains
localized in the inner part of the stripes. The complementarity of BLS and FMR
techniques, based on different selection rules, is found to be a fruitful tool
for the study of the wealth of localized mag-netic excitations generally found
in nanostructures.
