  Electrical generation of THz spin waves is theoretically explored in an
antiferromangetic nanostrip via the current-induced spin-orbit torque. The
analysis based on micromagnetic simulations clearly illustrates that the
Neel-vector oscillations excited at one end of the magnetic strip can propagate
in the form of a traveling wave when the nanostrip axis aligns with the
magnetic easy-axis. A sizable threshold is observed in the driving current
density or the torque to overcome the unfavorable anisotropy as expected. The
generated spin waves are found to travel over a long distance while the angle
of rotation undergoes continuous decay in the presence of non-zero damping. The
oscillation frequency is tunable via the strength of the spin-orbit torque,
reaching the THz regime. Other key characteristics of the spin waves such as
the phase and the chirality can also be modulated actively. The simulation
results further indicate the possibility of wave-like superposition between the
excited spin oscillations, illustrating its application as an efficient source
of spin-wave signals for information processing.
