  The discovery of current-induced spin-orbit torque (SOT) orthogonal
reorientation, also known as orthogonal switching, of metallic Mn$_2$Au and
CuMnAs has opened the door for ultrafast writing of an antiferromagnet (AFM).
Phenomenological theory predicts that the minimum field necessary for SOT
switching -- critical field -- for ultrashort pulses increases inversely
proportional to the pulse duration, thereby limiting the use of ultrafast
stimulus as driving force for switching. We explore the possibility that by
varying the working temperature the critical field reduces enabling orthogonal
switching in response to ultrashort pulses. To do so, we extend previous theory
to finite temperature and show that the critical field for an orthogonal
switching strongly depends on temperature. We determine how the temperature
dependence of the critical field varies as a function of the pulse duration.
While for long pulses, the temperature dependence of the critical field is
determined by the anisotropy field, for ultrashort pulses, it is determined by
the characteristic frequency of the AFM. We show that the short and long pulse
duration limits for the critical field can be connected by an analytical
expression.
