  We demonstrate analytically and numerically, that a thin film of an
antiferromagnetic (AFM) material, having biaxial magnetic anisotropy and being
driven by an external spin-transfer torque signal, can be used for the
generation of ultra-short "Dirac-delta-like" spikes. The duration of the
generated spikes is several picoseconds for typical AFM materials and is
determined by the in-plane magnetic anisotropy and the effective damping of the
AFM material. The generated output signal can consist of a single spike or a
discrete group of spikes ("bursting"), which depends on the repetition (clock)
rate, amplitude, and shape of the external control signal. The spike generation
occurs only when the amplitude of the control signal exceeds a certain
threshold, similar to the action of a biological neuron in response to an
external stimulus. The "threshold" behavior of the proposed AFM spike generator
makes possible its application not only in the traditional microwave signal
processing but also in the future neuromorphic signal processing circuits
working at clock frequencies of tens of gigahertz.
