  In the quantum anomalous Hall effect, chiral edge modes are expected to
conduct spin polarized current without dissipation and thus hold great promise
for future electronics and spintronics with low energy consumption. However,
spin polarization of chiral edge modes has never been established in
experiments. In this work, we theoretically study spin polarization of chiral
edge modes in the quantum anomalous Hall effect, based on both the effective
model and more realistic tight-binding model constructed from the first
principles calculations. We find that spin polarization can be manipulated by
tuning either a local gate voltage or the Fermi energy. We also propose to
extract spin information of chiral edge modes by contacting the quantum
anomalous Hall insulator to a ferromagnetic (FM) lead. The establishment of
spin polarization of chiral edge modes, as well as the manipulation and
detection in a fully electrical manner, will pave the way to the applications
of the quantum anomalous Hall effect in spintronics.
