Reconfigurable and self-biased magnonic metamaterials

Abstract

In magnonics, magnetic waves and oscillations are exploited for signal and information processing at microwave frequencies. A magnonic metamaterial is employed to configure different microwave bands by spatial engineering of magnetizations using different magnetic states or magnetic couplings. Magnetic field hysteretic variation of microwave responses has conventionally been used for tunable microwave operations. The use of such bias magnetic fields hinders the device integration of microwave magnonic devices. Here, we discuss a route to eliminating the requirement of bias magnetic field and simple initialization process for reconfigurable microwave operations. The distinct microwave responses are associated with different remanent magnetic states which are engineered by shape induced magnetic anisotropy rather than the conventional dipolar coupling driven magnetic states. However, the origin of the shift in the microwave spectra is associated with the variation of dipolar coupling for nanomagnetic networks, multilayer nanomagnets, and their arrays. This perspective provides an outlook on current challenges and potential future scopes of magnonic devices. We discuss some of our recent demonstrations toward the realizations of reconfigurable magnonic devices without any external bias magnetic field. Self-biased nanomagnets are also shown to have applications in designing a waveguide for spin wave transport and spin wave gating which operates without any bias magnetic field.