  Electrical switching of antiferromagnets (AFM) is critical for AFM
spintronics. However, there is an active debate about the mechanisms of
observed AFM switching on whether the switching is due to spin-orbit torques or
the much slower thermally-induced magnetoelastic effect. We report reliable
current-induced AFM switching in Pt/$\alpha$-Fe$_2$O$_3$ bilayers using
electrical pulses with various durations down to 0.3 ns. The dependence of
switching threshold current density on the pulse width indicates that
spin-orbit torques are the dominant mechanism responsible for electrical
switching of AFMs in the ns regime, reaffirming AFM spintronics as a promising
field for ultrafast and ultrahigh-frequency applications.
