  MnBi2Te4 has recently been predicted and shown to be a magnetic topological
insulator with intrinsic antiferromagnetic order. However, it remains a
challenge to grow stoichiometric MnBi2Te4 films by molecular beam epitaxy (MBE)
and to observe pure antiferromagnetic order by magnetometry. We report on a
detailed study of MnBi2Te4 films grown on Si(111) by MBE with elemental
sources. Films of about 100 nm thickness are analyzed in stoichiometric,
structural, magnetic and magnetotransport properties with high accuracy.
High-quality MnBi2Te4 films with nearly perfect septuple-layer structure are
realized and structural defects typical for epitaxial van-der-Waals layers are
analyzed. The films reveal antiferromagnetic order with a Neel temperature of
19 K, a spin-flop transition at a magnetic field of 2.5 T and a resistivity of
1.6 mOhm cm. These values are comparable to that of bulk MnBi2Te4 crystals. Our
results provide an important basis for realizing and identifying single-phase
MnBi2Te4 films with antiferromagnetic order grown by MBE.
