Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have identified previously unseen oscillation patterns known as Floquet states inside extremely small magnetic vortices. In contrast to earlier studies that relied on powerful laser pulses to generate these states, the Dresden team found that gentle stimulation using magnetic waves is enough. This discovery not only challenges existing ideas in fundamental physics but may also serve as a kind of universal connector linking electronics, spintronics, and quantum technologies. The findings were published in Science.
Magnetic vortices form in ultrathin disks made of materials like nickel-iron, often just micrometers or even nanometers in size. Inside these structures, tiny magnetic moments, which behave like miniature compass needles, align in circular patterns. When disturbed, waves ripple through the system in a way similar to a stadium crowd performing a coordinated “wave.” Each magnetic moment tilts slightly and passes its motion to the next, creating a chain reaction. These collective wave-like excitations are known as magnons.
“These magnons can transmit information through a magnet without the need for charge transport,” explains project leader Dr. Helmut Schultheiß from the Institute of Ion Beam Physics and Materials Research at HZDR. “This capability makes them highly attractive for research into next-generation computing technologies.”
Unexpected Frequency Combs in Tiny Magnetic Disks
The researchers had been experimenting with especially small magnetic disks, shrinking them from several micrometers down to just a few hundred nanometers. Their goal was to explore how disk size might influence neuromorphic computing, a brain-inspired approach to processing information. However, during data analysis, they noticed something unusual. Instead of a single resonance signal, some disks produced a series of closely spaced lines, forming what is known as a frequency comb.
“At first we assumed it was a measurement artifact or some kind of interference,” recalls Schultheiß. “But when we repeated the experiment, the effect reappeared. That is when it became clear we were looking at something genuinely new.”
Rotating Vortex Core Drives New Oscillation States
The explanation traces back to work by the French mathematician Gaston Floquet, who showed in the 19th century that systems exposed to periodic forces can develop entirely new oscillation states. Typically, creating these Floquet states has required large energy inputs, often delivered by intense laser pulses.
In this case, the researchers found that magnetic vortices can naturally produce Floquet states when magnons are sufficiently energized. The magnons transfer some of their energy to the vortex core, causing it to move in a tiny circular path around its center. Even this small motion is enough to rhythmically alter the magnetic state.
In experiments, this appears as a frequency comb. Instead of one sharp signal, multiple evenly spaced lines emerge, similar to how a pure tone can split into harmonics. “We were stunned that such a minute core motion was enough to transform the familiar magnon spectrum into a whole array of new states,” says Schultheiß.
Ultra-Low Energy Breakthrough With Big Potential
One of the most striking aspects of the discovery is how little energy it requires. While previous methods depended on high-powered lasers, this effect can be triggered with microwatts of power, far less than what a smartphone uses in standby mode.
This efficiency opens up new possibilities. Frequency combs generated in this way could help synchronize very different systems, connecting ultrafast terahertz signals with conventional electronics or even quantum devices. “We call it the universal adapter,” Schultheiß explains. “Just as a USB adapter allows devices with different connectors to work together, Floquet magnons could bridge frequencies that would otherwise remain incompatible.”
Toward Future Computing and Quantum Integration
The team plans to investigate whether the same mechanism can be applied to other magnetic structures. The discovery could play an important role in developing future computing systems by enabling communication between magnon-based signals, electronic circuits, and quantum components.
“On the one hand, our discovery opens new avenues for addressing fundamental questions in magnetism,” Schultheiß emphasizes. “On the other hand, it could eventually serve as a valuable tool to interconnect the realms of electronics, spintronics, and quantum information technology.”
All measurements of the magnetic vortices and analysis of data from multiple instruments were carried out using the Labmule program developed at HZDR, which is available as a lab automation tool.