  We demonstrate a new method of designing 2D functional magnetic topological
heterostructure (HS) by exploiting the vdw heterostructure (vdw-HS) through
combining 2D magnet CrI$_3$ and 2D materials (Ge/Sb) to realize new 2D
topological system with nonzero Chern number (C=1) and chiral edge state. The
nontrivial topology originates primarily from the CrI$_3$ layer while the
non-magnetic element induces the charge transfer process and proximity enhanced
spin-orbit coupling. Due to these unique properties, our topological magnetic
vdw-HS overcomes the weak magnetization via proximity effect in previous
designs since the magnetization and topology coexist in the same magnetic
layer. Specifically, our systems of bilayer CrI$_3$/Sb and trilayer
CrI$_3$/Sb/CrI$_3$ exhibit different topological ground state ranging from
antiferromagnetic topological crystalline insulator (C$_M$= 2) to a QAHE. These
nontrivial topological transition is shown to be switchable in a trilayer
configuration due to the magnetic switching from antiferromagnetism to
ferromangetism in the presence an external perpendicular electric field with
value as small as 0.05 eV/A. Thus our study proposes a realistic system to
design switchable magnetic topological device with electric field.
