Observation of the band structures of defect magnonic crystals

Kai Di, Vanessa Li Zhang, Meng Hau Kuok, Hock Siah Lim, Ser Choon Ng, Kulothungasagaran Narayanapillai, Hyunsoo Yang

Published 2014-06-19Version 1

Using Brillouin spectroscopy, the first observation has been made of the band structures of nanostructured defect magnonic crystals. The samples are otherwise one-dimensional periodic arrays of equal-width Ni80Fe20 and cobalt nanostripes, where the defects are stripes of a different width. A dispersionless defect branch emerges within the bandgap with a frequency tunable by varying the defect stripe width, while the other branches observed are similar to those of a defect-free crystal. Micromagnetic and finite-element simulations performed unveil additional tiny bandgaps and the frequency-dependent localization of the defect mode in the vicinity of the defects.