YMn₆Sn₆ exhibits topologically protected characteristics which are unusual given the underlying centrosymmetric crystal lattice (P6/mmm). In zero-applied magnetic field, polarized neutron diffraction measurements presented here show a preferential spin chirality in the double flat spiral spin state. At elevated temperatures and modest in-plane magnetic fields, a topological Hall effect emerges, [1,2] despite a null scalar spin chirality. The competing magnetic exchange interactions in this material are delicately balanced due to frustration and as a result, thermal fluctuations, temperature, and applied magnetic fields can drive the system into a number of different magnetic phases. Unpolarized neutron diffraction measurements were used to solve the structure of many of these phases and will also be presented. These measurements neatly explain the multiple features seen in ac susceptibility measurements, [1] and our corresponding theoretical studies align with the experimental evidence to provide a satisfyingly complete picture of the in-field magnetic phase diagram for YMn₆Sn₆.

[1] Ghimire, N. J., et al. arXiv preprint arXiv:2007.02399 (2020).
[2] Wang, Q., et al. arXiv preprint arXiv:1906.07986 (2019).