Band Structures Of Two-dimensional Magnonic Crystal Thin Film

In recent years, research efforts addressing spin wave(magnons) in micro- and nano-structured ferromagnetic materials have increased tremendously, in which magnonic crystals is a typical example. Magnonic crystal is a periodical structure of ferromagnetic system, and it is a young and evolving research field. The main purpose of this research is to manipulate the propagating behavior of spin waves at the micro- and nano-scale, and to provide the science evidence for the fabricating of spin signal processor. In analogy to photonic crystal taking control of the flow of light, magnonic crystal allows for the design of material properties for spin wave. But compared with photonic, phononic and other periodical structured composite materials, the research on magnonic crystal is more complicated. At the same scale of frequency, the wave length of spin wave is much shorter than that of electromagnetic wave, and so it is a big challenge for fabricating in experiment. In addition, the mechanism of magnetic interaction in the system with different lattice constants, which control the spin-wave propagation, is not quite same. Furthermore, the external magnetic field is another important factor determining the spin-wave dispersion relations, which will behave anisotropic dramatically. There are still existing significant challenges in this research field.The investigations on bulk magnonic crystals are relatively perfect.Compared with bulk magnonic crystal, the magnonic crystal thin film isparticularly interesting for discussing band formation mechanisms, and is easier to make in experiment. So the research focus of thin-film magnonic crystals is rising up now. In this paper, we investigate the magnonic band structure of in-plane magnetized two-dimensional magnonic crystals thin film at the nano-scale. Our analysis is based on the results of numerical calculations employed by the plane wave method. During the research work,we found that there are many factors affecting the band structures of magnonic crystals including shape of scatterers, filling fraction scatterers,arrangement of scatterers, material parameters, lattice constant and the external magnetic field. We have studied the effect of these factors to the band gap by calculating the different band structures.