Spin-wave phase inverter upon a single nanodefect.

Local modification of magnetic properties of nanoelements is a key to design future-generation signal processing systems in which information is encoded in the spin-wave phase. Among greatest challenges in nano-magnonics is keeping phase-setting elements tunable, simple, and miniature. Here, we successfully realize a tunable spin-wave phase shifter upon a single nanogroove milled by focused ion beam in a Co-Fe microsized magnonic waveguide. By increasing the groove depth and the in-plane biasing magnetic field we continuously tune the spin-wave phase and experimentally evidence a complete phase inversion. The microscopic mechanism of the phase shift is based on the combined action of the nanogroove as a geometrical defect and the lower spin-wave group velocity in the slice of the waveguide just below the groove where the magnetization is reduced due to the incorporation of Ga ions in consequence of the ion-beam milling. The proposed phase shifter can readily be on-chip integrated with spin-wave logic gates and other magnonic devices. Our findings are crucial for spin-wave phase-tuning in magnonic circuits and the generation of spin-wave beams by phased-array elements in spin-wave nano-optics.