Abstract-The generalized Fibonacci multiferroic superlattices (GFMS) are composed of single-phase multiferroic domains with simultaneous polarization and magnetization and are defined by the binary substitutional rule (B −→ B m A, A −→ B, m = 2, 3). We propose to construct a nonreciprocal multichannel bandstop filter by the GFMS. The couplings between electromagnetic waves and lattice vibration of multiferroic material with ferroelectric and ferromagnetic (or antiferromagnetic) orders can be invoked either through piezoelectric or piezomagnetic effects and can lead to the creation of polaritonic band structure. The plane wave expansion method with first-order approximation predicts the existence of multiple band gaps, and electromagnetic waves lying within the band gaps are prohibited, and the band gaps with respect to forward electromagnetic waves (FEWs) and backward electromagnetic waves (BEWs) are asymmetric. The forbidden band structures with FEWs and BEWs are calculated by the transfer matrix method and multiple frequency channels with unidirectional transmission of electromagnetic waves can be further confirmed. Nine and twenty transmission dips in transmission spectra for the BEWs in the frequency range ofω = 0.4-0.6 (17.06 GHz-25.59 GHz) are found in the GFMS with m = 2 and 3, respectively, in which the BEWs are prohibited while the FEWs can travel. Thus, the GFMS has all the conditions for the nonreciprocal multi-channel bandstop filter. Besides, the GFMS can also be applied to construct compact multi-channel one-way electromagnetic waveguides.

No abstract

The analytical solution of stress fields for an elastic elliptical inhomogeneity which includes a confocal rigid elliptical core and a screw dislocation under longitudinal shear is obtained explicitly in the series form by using the complex variable method. The influence of the rigid core on the interaction between screw dislocation and inhomogeneity is discussed. The image force acting on the screw dislocation is obtained. The results show that the rigid core in the inhomogeneity has strong influence on the interaction between screw dislocation and inhomogeneity. It can strengthen the repulsion to the dislocation when the inhomogeneity is hard, and weaken the attraction to the dislocation when the inhomogeneity is soft, whether the dislocation is in the inhomogeneity or in the matrix.

A novel reconfigurable band-stop filter using piezomagnetic-piezoelectric superlattices with the external direct-current (DC) electric field (PPSED) is presented. The center frequency of the forbidden band is reduced from to Hz in the band-stop filter as the thickness ratio of the piezoelectric domain to the piezomagnetic domain increases from to 9. The change of the forbidden bandwidth and the center frequency shows that the band-stop filter constructed by the PPSED is reconfigurable. The coupled polaritonic band structure is asymmetric with respect to the forward and backward directions and the forbidden bandwidth can be tuned by the DC electric field via the electro-optic effect. Unlike pure piezoelectric superlattices with the DC electric field, the forbidden bandwidth decreases with the increase of the electric field in the PPSED. The bandwidth tunability by the DC electric field can provide a guidance for the reconfigurable band-stop filter design to work in broadband frequencies.