  The one-dimensional planar magnonic crystals are usually fabricated as a
sequence of stripes intentionally or accidentally separated by non-magnetic
spacers. The influence of spacers on shaping the spin wave spectra is complex
and still not completely clarified. We performed the detailed numerical studies
of the one-dimensional single- and bi-component magnonic crystals comprised of
a periodic array of thin ferromagnetic stripes separated by non-magnetic
spacers. We showed that the dynamic dipolar interactions between the stripes
mediated by non-magnetic spacer, even ultra-narrow, significantly shift up the
frequency of the ferromagnetic resonance and simultaneously reduce the spin
wave group velocity, which is manifested by the flattening of the magnonic
band. We attributed these changes in the spectra to the modifications of
dipolar pinning and shape anisotropy both dependent on the width of the spacers
and the thickness of the stripes, as well as to the dynamical magnetic volume
charges formed due to inhomogeneous spin wave amplitude.
