Chirality in magnetic systems gives rise to a wide range of exotic phenomena, yet its influence in S=1 chains remains largely unexplored. Here, we present a comprehensive experimental study of a chiral antiferromagnetic (AFM) S=1 chain, [Ni(pym)(H2O)4]SO4⋅ H2O (pym = pyrimidine), where the Ni(II) octahedral orientation exhibits a four-fold chiral periodicity. Muon spin rotation measurements indicate the onset of long-range magnetic order below TN=1.82(2)K. Neutron diffraction measurements reveal a chiral AFM order driven by a chiral modulation of the easy-axis anisotropy direction, rather than the typical scenario of Dzyaloshinskii-Moriya interactions, geometrical frustration or higher-order interactions. Inelastic neutron scattering (INS) measurements reveal dispersive spin-wave excitations well described by linear spin-wave theory, with Hamiltonian parameters J0=6.81(1)K (intrachain exchange), J1a′=−0.091(1)K (interchain exchange), and D=−3.02(1)K (easy-axis single-ion anisotropy). These parameters are further validated by Monte Carlo simulations of the magnetisation. Additionally, the INS data reveal multiple dispersionless bands, suggesting the presence of further excitations beyond the scope of our linear spin-wave theory.
@article{arxiv.2509.07173,
title = {Single-ion anisotropy driven chiral magnetic order in a spin-1 antiferromagnetic chain},
author = {S. Vaidya and S. P. M. Curley and P. Manuel and J. Ross Stewart and M. Duc Le and A. Hernández-Melián and T. J. Hicken and C. Wang and H. Luetkens and J. Krieger and S. J. Blundell and T. Lancaster and K. A. Wheeler and D. Y. Villa and Z. E. Manson and J. A. Villa and J. L. Manson and J. Singleton and R. D. Johnson and P. A. Goddard},
journal= {arXiv preprint arXiv:2509.07173},
year = {2025}
}