Large magnonic band gaps and defect modes in one-dimensional comblike structures

We report the existence of large gaps in the band structure of a comblike s tructure composed of a one-dimensional magnonic waveguide along which N' da ngling side branches are grafted at N equidistant sites. These gaps origina te not only from the periodicity of the system but also from the resonance states of the grafted branches (which play the role of resonators). The wid th of these gaps is sensitive to the length of the side branches as well as to the numbers N and N'. The presence of defect branches in the comblike s tructure can give rise to localized states inside the gaps. We show that th ese states are very sensitive to the length of the side branches, to the pe riodicity, to N or/and N' and to the length of the defect branches. Analyti c expressions are given for the band structure of combs for large N and for the transmission coefficient for an arbitrary value of N and N' with and w ithout defects. [S0163-1829(99)09313-3].