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Stripe Helical Magnetism and Two Regimes of Anomalous Hall Effect in NdAlGe



Hung-Yu Yang, Jonathan N. Gaudet, Rahul Verma, Santu Baidya, Faranak Bahrami, Xiaohan Yao, Cheng-Yi Huang, Lisa Debeer-Schmitt, Adam A. Aczel, Guangyong Xu, Hsin Lin, Arun Bansil, Bahadur Singh, Fazel Tafti


We report the magnetic and electronic transport properties of the inversion and time-reversal symmetry breaking Weyl semimetal NdAlGe. This material is analogous to NdAlSi whose helicalmagnetism is a rare example of a Weyl-mediated collective phenomenon. We used neutron diffraction and found, just like NdAlSi, an incommensurate Ising spin density wave in NdAlGe with a small helical spin canting of 3(1)° and a long-wavelength of ∼ 35 nm. This incommensurate magnetism onsetsbelow Tinc = 6.8(2) K, and the spin structure transitions to a commensurate helical ferrimagnetic state below Tcom = 5.1(1) K. Using small-angle neutron scattering, we showed that the zero-field cooled ferrimagnetic domains form stripes in real space with characteristic length scales of 18(5) nm and 72(8) nm parallel and perpendicular to the [1,1,0] ordering vector direction, respectively. While the same type of Weyl-mediated helical magnetism as NdAlSi is revealed in NdAlGe, the transport properties of these two compounds are significantly different. Unlike the absence of anomalous Hall effect (AHE) in NdAlSi, we observe two regimes of AHE in NdAlGe that are respectively governed by intrinsic Berry curvature and extrinsic disorders/spin fluctuations. Our study suggests that Weyl-mediated magnetism may prevail in this group of noncentrosymmetric magnetic Weyl semimetals, while transport properties including AHE are generally more susceptible to material specifics such as disorders.
Physical Review Materials


Topological, Weyl, semi-metal, Neutron Diffraction, SANS, Anomalous Hall Effect


Yang, H. , Gaudet, J. , Verma, R. , Baidya, S. , Bahrami, F. , Yao, X. , Huang, C. , Debeer-Schmitt, L. , Aczel, A. , Xu, G. , Lin, H. , Bansil, A. , Singh, B. and Tafti, F. (2023), Stripe Helical Magnetism and Two Regimes of Anomalous Hall Effect in NdAlGe, Physical Review Materials, [online], (Accessed May 22, 2024)


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Created March 27, 2023, Updated September 26, 2023