  We report the dependence of the magnetization dynamics in a square artificial
spin-ice lattice on the in-plane magnetic field angle. Using two complementary
measurement techniques - broadband ferromagnetic resonance and micro-focused
Brillouin light scattering spectroscopy - we systematically study the evolution
of the lattice dynamics, both for a coherent radiofrequency excitation and an
incoherent thermal excitation of spin dynamics. We observe a splitting of modes
facilitated by inter-element interactions that can be controlled by the
external field angle and magnitude. Detailed time-dependent micromagnetic
simulations reveal that the split modes are localized in different regions of
the square network. This observation suggests that it is possible to
disentangle modes with different spatial profiles by tuning the external field
configuration.
