Spin wave propagation and nonreciprocity in metallic magnonic quasi-crystals

Abstract

Abstract The characteristics of spin waves (SWs) propagating in Fibonacci magnonic quasi-crystals (MQCs) were investigated in micromagnetic simulations. The SWs feel 1/3 of the characteristic Fibonacci sequence length as a period, and mini band gaps reflected by MQCs are formed. The effect of the MQC on the SW’s propagation becomes prominent above the first band gap frequency. The properties of SWs in MQCs generally depend on the propagation direction, because SWs feel different structures depending on the direction. Therefore, the nonreciprocity (NR) characteristics becomes complex. The NR characteristics change at every band gap frequency and hence across the frequency regions defined by them. In particular, some frequency regions have almost no NR, while others have enhanced NR and some have even negative NR. These characteristics seem to provide a new way to control NR.