  Quantum anomalous Hall (QAH) insulator is the key material to study emergent
topological quantum effects, but its ultralow working temperature limits
experiments. Here, by first-principles calculations, we find a family of stable
two-dimensional (2D) structures generated by lithium decoration of layered
iron-based superconductor materials FeX (X = S, Se, Te), and predict
room-temperature ferromagnetic semiconductors together with large-gap
high-Chern-number QAH insulators in the 2D materials. The extremely robust
ferromagnetic order is induced by the electron injection from Li to Fe and
stabilized by strong ferromagnetic kinetic exchange in the 2D Fe layer. While
in the absence of spin-orbit coupling (SOC), the ferromagnetism polarizes the
system into a half Dirac semimetal state protected by mirror symmetry, the SOC
effect results in a spontaneous breaking of mirror symmetry and introduces a
Dirac mass term, which creates QAH states with sizable gaps (several tens of
meV) and multiple chiral edge modes. We also find a 3D QAH insulator phase
featured by macroscopic number of chiral conduction channels in bulk
LiOH-LiFeX. The findings open new opportunities to realize novel QAH physics
and applications at high temperatures.
