Twisting Spins into a Spin-Wave Lens
Spintronic devices rely on flipping electron spins, which is faster and less costly in energy than shuttling charges in conventional electronics. The advantage is compounded if spin information is carried by spin waves rather than by moving the electrons themselves. Now Hongbin Wu at Tianjin University in China and colleagues have predicted that magnetic structures known as skyrmions could provide an effective means to control those waves [1].
Previous approaches to manipulating spin waves have relied on materials with painstakingly engineered spatial variations in their magnetic properties. Skyrmions, which are localized twists in a material’s magnetic texture, offer an alternative. That’s because spin waves interact with the skyrmion’s twistedness, which, like an effective magnetic field, deflects and scatters spin waves. Wu and colleagues showed theoretically that a skyrmion can instead act as a spin-wave lens, enabling more precise manipulation.
Wu and colleagues’ proposal depends on the Dzyaloshinskii-Moriya interaction (DMI), which arises from spin–orbit coupling in materials lacking spatial inversion symmetry. In causing neighboring spins to tilt slightly, the DMI stabilizes magnetic structures such as skyrmions and generates a magnetic-field-like effect for spin waves. The researchers found that, for a skyrmion in an antiferromagnetic film, this “pseudomagnetic field” has opposite poles at the core and the periphery. The resulting field gradient bends the wave fronts of spin waves, focusing planar waves to a point or collimating divergent ones.
The strength of the focusing effect depends on the strength of the DMI, which in turn depends on the presence of elements with strong spin–orbit coupling. Jin Lan, who led the research, says that meeting the material requirements should not be a major challenge.
–Marric Stephens
Marric Stephens is a Corresponding Editor for Physics Magazine based in Bristol, UK
References
- H. Wu et al., “Antiferromagnetic skyrmion as a magnonic lens,” Phys. Rev. B 113, 174431 (2026).