  Considerable efforts have recently been devoted to the experimental
realization of a two-dimensional Chern insulator, i.e., a system displaying a
quantum anomalous Hall effect. However, existing approaches such as those based
on magnetic doping of topological-insulator thin films have resulted in small
band gaps, restricting the effect to low temperatures. We use first-principles
calculations to demonstrate that an interface between thin films of the
topologically trivial ferromagnetic insulators EuO and GdN can result in a band
inversion and a non-zero Chern number. Both materials are stoichiometric and
the interface is non-polar and lattice-matched, which should allow this
interface to be achievable experimentally. We show that the band structure can
be tuned by layer thickness or epitaxial strain, and can result in Chern
insulators with gaps of over 0.1 eV.
