  Since the first experimental observation of all-optical switching phenomena,
intensive research has been focused on finding suitable magnetic systems that
can be integrated as storage elements within spintronic devices and whose
magnetization can be controlled through ultra-short single laser pulses. We
report here atomistic spin simulations of all-optical switching in multilayered
structures alternating n monolayers of Tb and m monolayers of Co. By using a
two temperature model, we numerically calculate the thermal variation of the
magnetization of each sublattice as well as the magnetization dynamics of
[Tbn/Com] multilayers upon incidence of a single laser pulse. In particular,
the condition to observe thermally-induced magnetization switching is
investigated upon varying systematically both the composition of the sample
(n,m) and the laser fluence. The samples with one monolayer of Tb as [Tb1/Co2]
and [Tb1/Co3] are showing thermally induced magnetization switching above a
fluence threshold. The reversal mechanism is mediated by the residual
magnetization of the Tb lattice while the Co is fully demagnetized in agreement
with the models developed for ferrimagnetic alloys. The switching is however
not fully deterministic but the error rate can be tuned by the damping
parameter. Increasing the number of monolayers the switching becomes completely
stochastic. The intermixing at the Tb/Co interfaces appears to be a promising
way to reduce the stochasticity. These results predict for the first time the
possibility of TIMS in [Tb/Co] multilayers and suggest the occurrence of
sub-picosecond magnetization reversal using single laser pulses.
