The interaction between conduction electrons and localized magnetic moments profoundly influences the electrical and magnetic properties of materials, giving rise to a variety of fascinating physical phenomena and quantum effects. Here, we discover a giant anomalous Hall effect (AHE) in a frustrated Eu-based magnet, exhibiting a giant anomalous Hall conductivity (AHC) of 31000 {\Omega}-1cm-1 and a remarkable anomalous Hall angle (AHA, tan{\theta}H) of 12 %--surpassing conventional mechanisms (either intrinsic or extrinsic) by two orders of magnitude. Combining magnetotransport, quantum oscillations, neutron diffraction and ab initio calculations, we establish that the giant AHC originates from fluctuating spin chirality skew scattering, generated by indirect Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions of Eu-4f moments. Simultaneously, Hund's coupling of itinerant electrons and localized Eu-4f spins triggers giant exchange splitting, evidenced by temperature-dependent Fermi surface reconstruction. This work establishes a frustrated magnetic platform for engineering the AHE and elucidates the governing role of exchange interactions and spin textures in quantum transport, while also providing a framework for designing unconventional spintronic systems that harness emergent spin-texture dynamics.
@article{arxiv.2603.14682,
title = {Giant anomalous Hall conductivity in frustrated magnet EuCo2Al9},
author = {Sheng Xu and Jian-Feng Zhang and Shu-Xiang Li and Junfa Lin and Xiaobai Ma and Wenyun Yang and Jun-Jian Mi and Zheng Li and Tian-Hao Li and Yue-Yang Wu and Jiang Ma and Qian Tao and Wen-He Jiao and Xiaofeng Xu and Zengwei Zhu and Yuanfeng Xu and Hanjie Guo and Tian-Long Xia and Zhu-An Xu},
journal= {arXiv preprint arXiv:2603.14682},
year = {2026}
}