Magnons are quasiparticles that represent quantized spin waves in magnetic materials. They can carry information without moving electric charge, making them promising for future information technologies that could use less energy than conventional electronics. The frequency, stability, and propagation distance of these waves are all important for their potential applications.
Now, a new study has found that changing the magnetic dimensionality of a layered material can significantly increase the frequency of spin waves. By adjusting the number of chromium vacancies in Cr2₋δTe2, researchers can increase the spin-wave frequency by more than five times.
The study, published in Newton on November 10, was led by Prof. SHENG Zhigao from the High Magnetic Field Laboratory at the Hefei Institutes of Physical Science of the Chinese Academy of Sciences.
In this study, the researchers focused on two Cr2₋δTe2 crystals with different concentrations of chromium vacancies. Using ultrafast spectroscopy measurements, they tracked how the spins processed in response to changes in magnetic dimensionality.
They found that increasing the chromium vacancy concentration changed the material's magnetic behavior from quasi-three-dimensional to quasi-two-dimensional. Along with this change, the spin-wave frequency rose from 37 to 194 GHz under a magnetic field of one tesla. At seven tesla, it reached 352 GHz.
The higher spin-wave frequency, however, came with stronger damping, meaning that the spin waves lost energy more quickly. The researchers found that stronger magnetic anisotropy was mainly responsible for the higher frequency, while scattering caused by chromium vacancies contributed to the increased damping. Weaker magnetic coupling between layers also restricted spin-wave propagation across the material, making the spin-wave motion more localized.
"By changing the magnetic dimensionality, we can control not only the frequency of spin waves but also how quickly they lose energy and how they propagate," SHENG said. "This understanding could help guide the design of high-frequency devices based on layered magnetic materials."
