  The recently synthesized silicene as well as theoretically discussed
germanene are examples of buckled honeycomb structures. The buckled structures
allow one to manipulate asymmetry between two underlying sublattices of
honeycomb structures. Here by taking germanene as a prototype of buckled
honeycomb lattices, we explore magnetism induced by breaking sublattice
symmetry through saturating chemical bonds on one-side of the buckled honeycomb
lattice. It is shown that when fractions of chemical bonds on one-side are
saturated, two narrow bands always exist at half filling. Furthermore, the
narrow bands generally support flat band ferromagnetism in the presence of the
Hubbard $U$ interaction. The induced magnetization is directly related to the
saturation fraction and is thus controllable in magnitude through the
saturation fraction. Most importantly, we find that depending on the saturation
fraction, the ground state of an one-side saturated germanene may become a
quantum anomalous Hall (QAH) insulator characterized by a Chern number that
vanishes for larger magnetization. The non-vanishing Chern number for smaller
magnetization implies that the associated quantum Hall effect tends to survive
at high temperatures. Our findings provide a potential method to engineer
buckled honeycomb structures into high-temperature QAH insulators.
