  Single femtosecond pulse toggle switching of ferrimagnetic alloys is an
essential building block for ultrafast spintronics. Very different
element-specific demagnetization dynamics is believed to be a hard limit for
switching in ferrimagnets. This suggests that ferrimagnets composed of two ions
of different nature, such as rare earth transition metal alloys, are necessary
for switching. However, experimental observation of toggle switching in
Mn$_2$Ru$_x$Ga Heusler alloys, has contested this limit since Mn ions are of
the same nature. To shed some light into this question, we present an atomistic
spin model for the simulation of single pulse toggle switching of
Mn$_2$Ru$_x$Ga. The magnetic parameters entering in our model are extracted
from previous experimental observations. We show that our model is able to
quantitatively reproduce measured magnetization dynamics of single pulse toggle
switching. We demonstrate that differently to previous understanding toggle
switching in Mn$_2$Ru$_x$Ga is possible even when both Mn sublattices
demagnetization at very similar rate.
