Scientists from the University of Exeter, Diamond Light Source, Advanced Light Source, the University of Oxford and UC Berkeley reveal that a spin current in an insulating antiferromagnet is mediated by coherent evanescent spin waves. Their work, published in Physical Review Letters, utilizes the capabilities of element specific x-ray ferromagnetic resonance (XFMR), which enables the detection of both phase and amplitude of the transmission of pure spin current through the antiferromagnet.
Recent experiments have demonstrated that pure spin currents may be transported over long distances within antiferromagnetic materials (AFMs) and that antiferromagnetic domains can be switched electrically. Since AFMs are insensitive to stray magnetic fields and can be resonantly excited at THz frequencies, they show outstanding promise for use in spintronic applications. However, to realise the full potential of AFMs, it is essential to explore the coherence of the spin currents that they mediate, since the phase of the spin current provides an additional degree of freedom for exploitation within information processing.
For the full story, please read the Diamond Highlight!
Maciej Dąbrowski, Takafumi Nakano, David M. Burn, Andreas Frisk, David G. Newman, Christoph Klewe, Qian Li, Mengmeng Yang, Padraic Shafer, Elke Arenholz, Thorsten Hesjedal, Gerrit van der Laan, Zi Q. Qiu, and Robert J. Hicken. Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO, Phys. Rev. Lett. 124, 217201 (2020).
See also the viewpoint by Helena Reichlova, Richard Schlitz, and Sebastian T. B. Goennenwein: Spin current in an antiferromagnet is coherent, Physics 13, 83 (2020).