  Topological insulators are new states of quantum matter in which surface
states residing in the bulk insulating gap are protected by time-reversal
symmetry. When a proper kind of antiferromagnetic long range order is
established in a topological insulator, the system supports axionic
excitations. In this paper, we study theoretically the electronic states in a
transition metal oxide of corundum structure, in which both spin-orbit
interaction and electron-electron interaction play crucial roles. A
tight-binding model analysis predicts that materials with this structure can be
strong topological insulator. Because of the electron correlation, an
antiferromagnetic order may develop, giving rise to a topological magnetic
insulator phase with axionic excitations.
