Reconfigurable magnonic metamaterial for microwave signal processing

Abstract

We propose a reconfigurable magnonic metamaterial based on an array of dipolarly-coupled magnetic nano-pillars having perpendicular shape anisotropy. The static magnetic ground state of such a metamaterial is antiferromagnetic (AFM), and a linear defect in the form of ferromagnetically (FM) ordered chain of nano-pillars can act as a waveguide supporting a strongly localized spin wave on the linear defect whose frequency is well-separated from the bulk spin wave spectrum of the metamaterial. The phase of this localized SW can be controlled by placing an additional point defect (a pillar with inverted magnetization direction) near the waveguide. In our case the phase shift is close to π radians, which corresponds to the operation of the phase inverter working without an external bias magnetic field. Since the phase shift is achieved by changing the orientation of magnetization of a single pillar, it is possible to dynamically control this phase shift. Also, by changing the orientation of the pillars placed further from the waveguide it is possible to vary the magnitude of the phase shift without significant changes in the spin wave amplitude.