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Antiferromagnetic spin chains: ground states and phase transitions in static magnetic field of arbitrary direction

Borysenko, Y.; Sheka, D.; Yershov, K.; Faßbender, J.; van den Brink, J.; Makarov, D.; Pylypovskyi, O.


While easy axis antiferromagnets (AFMs) are robust against external magnetic fields of a moderate strength, spin reorientations in strong fields provide an insight into subtle properties of materials, which are usually hidden by the high symmetry of the ground state [1]. In absence of external magnetic fields, they reveal geometry-driven chiral and anisotropic responses supplemented by weak ferromagnetism [2]. Here, we address theoretically the effects of curvature in achiral anisotropic ring-shaped AFM spin chains exposed to strong magnetic fields using the methodology of curvilinear magnetism [3]. We identify the geometry-governed helimagnetic phase transition enabled in the spin-flop phase, separating locally homogeneous (vortex) and periodic (onion) AFM textures (Fig. 1). The curvature-induced Dzyaloshinskii–Moriya interaction results in the spin-flop transition being of the first- or second-order depending on the ring curvature. Spatial inhomogeneity of the Néel vector in the spin-flop phase generates the weakly ferromagnetic esponse in the plane perpendicular to the applied magnetic field, which is inherent to curved systems. In AFM spin chains possesing torsion, e.g. helices, these effects are enhanced by the inhomogeneity of local texture in the ground state. Our work provides further insights in the physics of curvilinear AFMs in static magnetic fields and guides prospective experimental studies of geometrical effects in the spin-chain nanomagnets.

Keywords: antiferromagnetism; curvilinear spin chains

  • Lecture (Conference)
    AIM 2023 Advances in Magnetics, 15.-18.01.2023, Moena, Italy, 15.-18.01.2023, Moena, Italy


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