  To design fast memory devices, we need material combinations which can
facilitate fast read and write operation. We present a heterostructure
comprising a two-dimensional (2D) magnet and a 2D topological insulator (TI) as
a viable option for designing fast memory devices. We theoretically model
spin-charge dynamics between the 2D magnets and 2D TIs. Using the adiabatic
approximation, we combine the non-equilibrium Green's function method for
spin-dependent electron transport, and time-quantified Monte-Carlo for
simulating magnetization dynamics. We show that it is possible to switch the
magnetic domain of a ferromagnet using spin-torque from spin-polarized edge
states of 2D TI. We further show that the switching between TIs and 2D magnets
is strongly dependent on the interface exchange ($J_{\mathrm{int}}$), and an
optimal interface exchange depending on the exchange interaction within the
magnet is required for efficient switching. Finally, we compare the
experimentally grown Cr-compounds and show that Cr-compounds with higher
anisotropy (such as $\rm CrI_3$) results in lower switching speed but more
stable magnetic order.
