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, 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 twofold 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 (AFM) 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 paper highlights the symmetry-broken interface of AFM materials as a means of exploring topological effects and their relevant applications.
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This work was supported by the Research Center Program of the Institute for Basic Science in Korea (Grants No. IBS-R009-D1 and No. IBS-R009-G1). The work at the National High Magnetic Field Laboratory was supported by the National Science Foundation Cooperative Agreement Grant No. DMR-1157490 and the State of Florida. T.O. and B.J.Y. acknowledge the support of the Research Resettlement Fund for new faculty of Seoul National University and the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (Grant No. 0426-20150011). J.H.G. and A.S. acknowledge the support of National Science Foundation Grant No. DMR-1454200.
Kim, Woo Jin; Gruenewald, John H.; Oh, Taekoo; Cheon, Sangmo; Kim, Bongju; Korneta, Oleksandr B.; Cho, Hwanbeom; Lee, Daesu; Kim, Yoonkoo; Kim, Miyoung; Park, Je-Geun; Yang, Bohm-Jung; and Seo, Ambrose, "Unconventional Anomalous Hall Effect from Antiferromagnetic Domain Walls of Nd2Ir2O7 Thin Films" (2018). Physics and Astronomy Faculty Publications. 633.