Integrated tunable magnonic devices for beyond 6 GHz signal processing
In the search for novel technology platforms supporting the transition towards ''beyond 6G'' telecommunications, magnonics is emerging as a viable route, primarily due to its intrinsic compatibility with the UWB-FR3 bands and its easy tunability. In this paper, we present a proof-of-concept device based on a CoFeB magnonic waveguide, fully integrated on silicon, which demonstrates all the key features of our integration approach, based on co-integrated hard magnetic micromagnets, magnonic conduits, reconfigurable soft magnetic elements and MEMS. The bias field enabling operation up to about 12 GHz is provided by SmCo micromagnets embedded in the silicon substrate. Real-time tunability is implemented in two ways. First, current-driven control is achieved via an integrated current line that generates an additional localized magnetic field, enabling continuous tuning of Backward Volume spin-wave propagation. Second, we achieve voltage-controlled tunability by integrating a NiFeMo soft magnetic element onto a piezoelectric MEMS cantilever and flip-chipping it onto the magnonic device. Upon actuation, the cantilever brings the NiFeMo into proximity with the permanent micromagnets, where it captures the stray field. The resulting voltage-controlled displacement modulates the coupling between the hard and soft magnetic components, effectively reducing the local bias field on the CoFeB waveguide and enabling fine control of Damon--Eshbach spin waves.