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 with noncoplanar 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 noncoplanar antiferromagnet, $\mathrm{N}{\mathrm{d}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$. Bulk $\mathrm{N}{\mathrm{d}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$ has a cubic symmetry; thus, its Hall signal should be zero without an applied magnetic field. The DWs generated in this material break the twofold rotational symmetry, which allows for finite anomalous Hall conductivity. A strong $f\text{−}d$ exchange interaction between the Nd and Ir magnetic moments significantly influences antiferromagnetic (AFM) domain switching. Our epitaxial $\mathrm{N}{\mathrm{d}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7$ 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 paper highlights the symmetry-broken interface of AFM materials as a means of exploring topological effects and their relevant applications.

• Received 1 December 2017
• Revised 12 April 2018

DOI:https://doi.org/10.1103/PhysRevB.98.125103