'Spin-based electronics or 'spintronics', that exploits spin current, has the potential to be not just significantly faster, but also more energy-efficient.

Scientists have recently discovered that some electrically insulating antiferromagnetic materials are exceptionally good conductors of pure spin current.

In the new research, scientists from Exeter, in collaboration with the Universities of Oxford, California Berkeley, and the Advanced and Diamond Light Sources, have experimentally demonstrated that high frequency alternating spin currents can be transmitted by, and sometimes amplified within, thin layers of antiferromagnetic NiO.

The results demonstrate that the spin current in thin NiO layers is mediated by evanescent spin waves, a mechanism akin to quantum mechanical tunneling.

The use of thin NiO layers for transfer and amplification of ac spin current at room temperature and gigahertz frequencies may lead to more efficient future wireless communication technology.

Physical Review Letters – Coherent Transfer of Spin Angular Momentum by Evanescent Spin Waves within Antiferromagnetic NiO

Insulating antiferromagnets have recently emerged as efficient and robust conductors of spin current. Element-specific and phase-resolved x-ray ferromagnetic resonance has been used to probe the injection and transmission of ac spin current through thin epitaxial NiO(001) layers. The spin current is found to be mediated by coherent evanescent spin waves of GHz frequency, rather than propagating magnons of THz frequency, paving the way towards coherent control of the phase and amplitude of spin currents within an antiferromagnetic insulator at room temperature.