Theory of dual-tunable thin-film multiferroic magnonic crystal.

A theory has been developed for the waveguiding characteristics of dual-tunable multiferroic magnonic crystals (MCs). The crystals are constructed as periodically width-modulated microwave transmission slot-lines placed in between thin ferrite and ferroelectric films. Dispersion characteristics of the spin-electromagnetic waves (SEWs) in the investigated periodic waveguiding structure were derived using the method of approximate boundary conditions and the coupled-mode approach. The transmission-loss characteristics (TLCs) were calculated by the transfer-matrix method. The results show that the TLCs of the structures consist of pass-bands and stop-bands. The stop-bands are due to Bragg reflections in the structure. The magnetic and electric fields control the stop-band frequencies. The ferroelectric film polarization produced with the application of control voltage to the slot-line electrodes reduces its dielectric permittivity and provides up-shift of the stop-band frequencies. The most effective electric tuning is achieved in the area of the maximum hybridization of SEWs. As a result, the investigated multiferroic MCs combine the advantages of thin-film planar topology and dual tunability of magnonic band-gaps. [ABSTRACT FROM AUTHOR]