Chiral and anisotropic responses in curved anitferromagnetic spin chains

Geometry-driven effects in magnetism arise due to (i) sample boundaries, (ii) non-zero curvature of low-dimensional magnets and (iii) non-trivial sample’s geometry. For ferromagnets, all these directions are under intensive studies for a long time, with the primary driver being shape anisotropy stemming from magnetostatics [1]. Antiferromagnets (AFMs) possess more complex magnetic ordering, with a much less fundamental understanding of the interplay between geometry and magnetic textures.The simplest systems uncovering the specific features of AFM exchange in curvilinear geometries are spin chains, which can be arranged along plane and space curves. The dipolar interaction provides the strong hard-axis shape anisotropy for AFM spin chains. Break of the spatial inversion symmetry by geometry leads to the appearance of the chiral response of Dzyaloshinsksii-Moriya interaction symmetry, which enables geometry-driven helimagnetic phase transition for chains along space curves [2]. The weak easy axis for the Neel vector comes from the exchange-driven anisotropy [2]. The presence of the easy axis and easy-plane anisotropies in total allows to observe the field-driven spin-reorientation transitions with the critical fields proportional to the curvature and a family of the topologically different states in spin-flop phase [3]. Furthermore, localized curvature behaves as the effective pinning potential for non-collinear antiferromagnetic textures [4]. [1] D. Sheka, Appl. Phys. Lett., 118, 230502 (2021); D. Makarov et al. Adv. Mater., 34, 2101758 (2022)
[2] O. Pylypovskyi, D. Kononenko et al, Nano Lett., 20, 8157–8162 (2020)
[3] O. Pylypovskyi et al, App. Phys. Lett., 118, 182405 (2021); Y. Borysenko et al., Phys. Rev. B, 106, 174426 (2022)
[4] K. Yershov, Phys. Rev. B, 105, 064407 (2022)