Researchers at Argonne National Laboratory and the University of Illinois Urbana-Champaign have developed a method to generate spontaneous magnons in yttrium iron garnet that can be tuned to an external signal. The results, reported in Nature Communications, point toward new approaches for information processing in next-generation microelectronics, wireless communication, and quantum devices.
Magnons are disturbances or waves that travel through magnetic materials. Scientists already know how to create them in thin magnetic films, but producing oscillations that are both self-sustaining and steadily rhythmic in response to an outside cue has remained more difficult. Stable, controllable magnons could offer a way to deliver and process information that other types of waves cannot match.
The team used a technique called parametric pumping. The process begins with a pair of microwave antennas placed on a yttrium iron garnet film only a couple hundred nanometers thick. The small antenna dimensions allow precise control over the spontaneous oscillations. An external signal then adjusts the magnons, producing phase-locking in which the magnetic waves adapt to match the rhythm of the incoming signal.
Yi Li, an assistant scientist at Argonne and one of the study’s lead authors, explained the advantage. “Parametric pumping usually creates chaotic wave motions, and it is hard to use the chaos for applications. With our method, we can create ultrasharp waves that are highly controllable.”
Valentine Novosad, Argonne Distinguished Fellow, senior scientist and lead co-author, said the advance allows researchers to move from disordered waves to tightly controlled, synchronized oscillations. “We can now control the transition from those chaotic wave motions to tightly controlled, phase-locked, in-sync magnon oscillations.”
The demonstration took place in a classical system at room temperature. The same controlled dynamics are relevant to hybrid superconducting-magnonic systems under development for quantum information science through a Department of Energy-funded project.
“We are exploring new physics and working to understand the building blocks of these future systems,” Novosad said.
The yttrium iron garnet component was fabricated at the Center for Nanoscale Materials, a Department of Energy Office of Science user facility at Argonne. The work also drew on the Midwest quantum research ecosystem, including contributions from undergraduate and early-career researchers connected through the Chicago Quantum Exchange and University of Illinois collaborations.
Axel Hoffmann, founder professor at the University of Illinois and lead co-author, noted that the finding emerged from fundamental characterization work rather than a targeted search. “We did not say, ‘OK, let’s go look for this particular effect.’ It was more that we were trying to characterize microwave signals in these devices, and these signals popped up, leading us to drill down more. The strength of fundamental science is that you can explore ideas.”
Li said the next step is to connect the effect to on-chip circuits or qubits. “More broadly, this work provides a new way to generate and control coherent magnon signals, which could be useful for low-power microwave signal processing and future computing architectures.”
The research was supported by the Department of Energy’s Office of Science, the National Science Foundation, Argonne’s Laboratory Directed Research and Development program, and Q-NEXT, a Department of Energy National Quantum Information Science Research Center led by Argonne.
