Scientists at the Helmholtz-Zentrum Dresden-Rossendorf have discovered previously unseen Floquet states inside extremely small magnetic vortices using minimal energy from magnetic waves. This finding, which challenges prior assumptions, could link electronics, spintronics, and quantum technologies. The results appear in Science.
Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) identified unusual oscillation patterns, known as Floquet states, within magnetic vortices in ultrathin disks made of materials like nickel-iron. These disks measure just micrometers or nanometers across, where magnetic moments align in circular patterns akin to miniature compass needles forming whirlpools. When stimulated, these structures produce magnons—collective wave-like excitations that propagate information without charge transport, making them promising for future computing. Dr. Helmut Schultheiß, project leader at HZDR's Institute of Ion Beam Physics and Materials Research, noted: 'These magnons can transmit information through a magnet without the need for charge transport.' The team shrank the disks to a few hundred nanometers to study effects on neuromorphic computing but observed frequency combs—series of closely spaced lines—instead of single resonance signals. Schultheiß recalled: 'At first we assumed it was a measurement artifact or some kind of interference. But when we repeated the experiment, the effect reappeared.' The phenomenon arises from magnons energizing the vortex core, causing it to trace a tiny circular path that rhythmically alters the magnetic state, generating the combs with just microwatts of power—far less than a smartphone in standby. Unlike methods requiring intense laser pulses, this uses gentle magnetic waves. Schultheiß described it as a 'universal adapter,' akin to a USB port, potentially synchronizing terahertz signals with electronics or quantum devices. The discovery, detailed in a paper by Christopher Heins and colleagues in Science (DOI: 10.1126/science.adq9891), was analyzed using HZDR's Labmule program. The team aims to explore applications in other magnetic structures for interconnecting electronics, spintronics, and quantum information technology.
