Antiferromagnetic resonance excited by oscillating electric currents

In antiferromagnetic materials, the order parameter exhibits resonant modes at frequencies that can be in the terahertz range, which makes them highly interesting for novel spintronics applications. In this work, I theoretically explore the possibility of exciting antiferromagnetic resonance by the spin-Hall effect in a system consisting of an antiferromagnetic insulator (AFM) coupled to a normal metal wave guide. The time-dependent interplay between the spin-accumulation and the AFM degrees of freedom is studied. It is shown that near antiferromagnetic resonance, the balancing of the spin currents in the normal metal is re-adjusted, and as a consequence the net charge current through the waveguide is altered, leading to an imprint of the AFM dynamics on the frequency-dependent waveguide conductivity. In addition, the relative contributions of spin-torque and current-induced Oersted field to the AFM excitation are compared, showing that resonant excitation by spin-currents can be orders of magnitude more efficient than excitation by the Oersted field.