  We report on the evolution of the spin-wave spectrum under structural
disorder introduced intentionally into one-dimensional magnonic quasicrystal.
We study theoretically a system composed of ferromagnetic strips arranged in a
Fibonacci sequence. We considered several stages of disorder in the form of
phasonic defects, where different rearrangements of strips are introduced. By
transition from the quasiperiodic order towards disorder, we show a gradual
degradation of spin-waves fractal spectra and closing of the frequency gaps. In
particular, the phasonic defects lead to the disappearance of the van Hove
singularities at the frequency gap edges by moving modes into the frequency
gaps and appearing new modes inside the frequency gaps. These modes disperse
and eventually can close the gap, with increasing disorder levels. The work
reveals how the the presence of disorder modifies the intrinsic spin wave
localization existing in undefected magnonic quasicrystals. The paper
contributes to the knowledge of magnonic Fibonacci quasicrystals and opens the
way to study of the phasonic defects in two-dimensional magnonic quasicrystals.
