  The magnetic van der Waals crystals MnBi2Te4/(Bi2Te3)n have drawn significant
attention due to their rich topological properties and the tunability by
external magnetic field. Although the MnBi2Te4/(Bi2Te3)n family have been
intensively studied in the past few years, their close relatives, the
MnSb2Te4/(Sb2Te3)n family, remain much less explored. In this work, combining
magnetotransport measurements, angle-resolved photoemission spectroscopy, and
first principles calculations, we find that MnSb4Te7, the n = 1 member of the
MnSb2Te4/(Sb2Te3)n family, is a magnetic topological system with versatile
topological phases which can be manipulated by both carrier doping and magnetic
field. Our calculations unveil that its A-type antiferromagnetic (AFM) ground
state stays in a Z_2 AFM topological insulator phase, which can be converted to
an inversion-symmetry-protected axion insulator phase when in the ferromagnetic
(FM) state. Moreover, when this system in the FM phase is slightly carrier
doped on either the electron or hole side, it becomes a Weyl semimetal with
multiple Weyl nodes in the highest valence bands and lowest conduction bands,
which are manifested by the measured notable anomalous Hall effect. Our work
thus introduces a new magnetic topological material with different topological
phases which are highly tunable by carrier doping or magnetic field.
