  Ferroic domain walls (DWs) create different symmetries and ordered states
compared with those in single-domain bulk materials. In particular, the DWs of
an antiferromagnet (AFM) with non-coplanar spin structure have a distinct
symmetry that cannot be realized in those of their ferromagnet counterparts. In
this paper, we show that an unconventional anomalous Hall effect (AHE) can
arise from the DWs of a non-coplanar AFM, Nd2Ir2O7. Bulk Nd2Ir2O7 has a cubic
symmetry; thus, its Hall signal should be zero without an applied magnetic
field. The DWs generated in this material break the two-fold rotational
symmetry, which allows for finite anomalous Hall conductivity. A strong f-d
exchange interaction between the Nd and Ir magnetic moments significantly
influences antiferromagnetic domain switching. Our epitaxial Nd2Ir2O7 thin film
showed a large enhancement of the AHE signal when the AFM domains switched,
indicating that the AHE is mainly due to DWs. Our study highlights the symmetry
broken interface of AFM materials as a new means of exploring topological
effects and their relevant applications.
