Phase shifter based on voltage-controlled magnetic domain walls

Abstract

A controllable phase shifter is an essential part of spin-wave (SW) logic devices. Magnetic domain walls (DWs) as magnonic waveguides have been used to study SW propagation in ultrathin ferromagnetic films. In this study, we present a channel for SW propagation that relies on magnetic DWs as natural waveguides and realize phase manipulation by voltage-controlled magnetic anisotropy (VCMA) at a lower excitation frequency with micromagnetic simulations. The system model is a double-layer magnetic film structure, containing two oppositely magnetized domains and an upper layer (Co20Fe60B20) coupled with the lower layer ([Co/Pd]) through exchange interaction. The pinning structure can effectively maintain the state of the waveguide during later operation without an additional magnetic field. By numerical micromagnetic simulation, we can clearly see that the exchange-dominated isotropic magnetostatic forward volume like SWs are confined in the Bloch-type DW. The phase accumulation by a propagating SW depends on the accumulated phase wave vector (k) and the distance traveled. Therefore, SWs accumulate more phase through DW waveguides covered by electrodes with different lengths. The phase of the SW is shifted after the SW passes through the voltage region, compared with the waveguide where a voltage is unapplied. As a result, the established phase shifter shows a phase difference of 2π by applying a voltage (E = 1 V/nm), and the length of the applied electrode is about 644 nm.