  Magnetic skyrmions are promising candidates for future information storing
and processing devices. There are different routes for stabilizing the
skyrmions. Understanding the interplay mechanism between different scenarios of
skyrmion formation is one key factor that can reveal new paths for controlling
skyrmion phases. Inspired by the flexibility of two-dimensional materials that
offer an exciting playground for manipulating spin textures, we conducted
\textit{ab initio} simulations and utilized four-state spin framework to
determine magnetic parameters of lateral heterostructure formed by NiBr2 and
NiCl2 Monolayers. The obtained spin interaction parameters are utilized to
determine the skyrmionic phases via Monte Carlo simulation. Monte Carlo
simulation results suggest three distinct phase transition mechanisms exist in
the present system. Namely, examination of heat capacity versus temperature
curve obtained from average anisotropic exchange energy yields a phase
transition between paramagnetic and spin-spiral states at $5$K for pristine
NiBr2, a paramagnetic-mixed skyrmion state transition occurs at 17 K for
pristine NiCl2, and a high-temperature ferromagnetic-paramagnetic transition at
T=80 K is observed for the heterostructure region, indicating that some kind of
intrinsic ferromagnetism may originate at the interface of pristine Janus
structures.
