  The quantum anomalous Hall effect is a intriguing topological nontrivial
phase arising from spontaneous magnetization and spin-orbit coupling. However,
the tremendously harsh realizing requirements of the quantum anomalous Hall
effects in magnetic topological insulators of Cr or V-doped (Bi,Sb)2Te3 film,
hinder its practical applications. Here, we use first principles calculations
to predict that the three Mn2O3 structure is an intrinsic ferromagnetic Chern
insulator. Remarkably, a quantum anomalous Hall phase of Chern number C = -2 is
found, and there are two corresponding gapless chiral edge states appearing
inside the bulk gap. More interestingly, only a small tensile strain is needed
to induce the phase transition from Cmm2 and C222 phase to P6/mmm phase.
Meanwhile, a topological quantum phase transition between a quantum anomalous
Hall phase and a trivial insulating phase can be realize. The combination of
these novel properties renders the two-dimensional ferromagnet a promising
platform for high effciency electronic and spintronic applications.
