  It is of great interest to explore intrinsic two-dimensional ferromagnetism
and seek better two-dimensional quantum anomalous Hall insulator materials.
Here, we show that the FeBr$_3$ monolayer is an intrinsic two-dimensional
ferromagnetic material whose Curie temperature is 140 K thanks to its strong
spin exchange interaction and giant uniaxial magnetic anisotropy. Our phonon
spectra and mechanical analysis indicate that the FeBr$_3$ monolayer is
dynamically and mechanically stable. Our electronic structure calculation shows
that there is one Dirac cone at K point in the Brillouin zone and the
spin-orbit coupling opens a semiconductor gap of 33.5 meV. Further
tight-binding analysis reveals that the Chern number is equivalent to 1 and
there is a quantum anomalous Hall conductivity $\sigma _{xy} = e^2/h$, and the
chiral edge states are fully spin-polarized when an edge is created.
Furthermore, it is shown that the main results are not affected by electron
correlation effects and biaxial strain. Therefore, this FeBr$_3$ monolayer as
2D material would be useful for spintronic applications.
