Spin wave surface states in 1D planar magnonic crystals

We have investigated surface spin wave states in 1D planar bi-component magnonic crystals, localized on the surfaces resulting from the breaking of the periodic structure. The two systems have been considered: the magnonic crystal with periodic changes of the anisotropy field in an exchange regime and the magnonic crystal composed of Fe and Ni stripes in a dipolar regime with exchange interactions included. We chose the symmetric unit cell for both systems to implement the symmetry related criteria for existence of the surface states. We investigated also the surface states induced by the presence of perturbation of the surface areas of the magnonic crystals. We showed that the system with modulated anisotropy is a direct analog of the electronic crystal. Therefore, the surface states in both systems have the same properties. For the surface states existing in magnonic crystals in dipolar-exchange regime we demonstrated that the spin waves show distinct differences in comparison to the electronic crystals, which are due to long-range dynamic dipolar interactions. We found that tuning of the strength of magnetization pinning, resulting from the surface anisotropy or dipolar effect, is vitally important for the existence of surface states in magnonic crystals. (paper)