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: In the centre of our here presented work was the Heusler compound Mn1.4PtSn characterized by anisotropic DMI and known to host various chiral spin textures. In this study, we employed a combination of REXS and micromagnetic simulations to reveal distinct features consistent with a fan-like [1] spin structure and its field driven evolution under increasing in-plane magnetic fields. Starting from the chiral ground state (π-CSL [2]) of Mn1.4PtSn, this field-induced transition is accompanied by a change in the quasi-one-dimensional magnetic topology via symmetry breaking. The resulting fan state exhibits oscillatory spin arrangements confined to a finite angular range about the field direction and lacks topological winding.
Fan structures are traditionally observed in non-chiral systems such as Yoshimori-type helimagnets, where competing nearest- and next-nearest-neighbor exchange interactions stabilize helices of both chiralities [2]. These can smoothly transform into fan phases under transverse magnetic fields without an energy penalty [1,4]. In contrast, the emergence of a fan-like spin texture in chiral magnets such as Mn1.4PtSn is unusual. Here, DMI enforces a fixed chirality, making the fan energetically unfavorable by the DMI [1]. Historically, this has excluded fan states from consideration in DMI-active systems.
Only recently, LTEM studies on the monoaxial helimagnet MnNb3S6 have reported domain-like patterns reminiscent of fan structures [6,7]. However, due to limited spatial resolution and similarities with stripe phases, these observations remain inconclusive [8]. Building on these findings, we present the first unambiguous experimental identification of fan-like magnetic textures in a chiral magnet, resolving ambiguities that have limited previous observations.
References:
1. Izyumov, Y.A. “Modulated, or long-periodic, magnetic structures of crystals” Sov. Phys. Usp. 27 845 (1984).
2. Winter et al. "Magnetic field-induced condensation of π to 2π soliton lattices in chiral magnets."(to be submitted).
3. Yoshimori, A., “A New Type of Antiferromagnetic Structure in the Rutile Type Crystal“ JPSJ, 14, 807-821 (1959).
4. Ishikawa, Y., et al., “Transformation to Fan Spin Structure by External Field in Ferromagnetic MnP”, PRL 23, 532 (1969).
5. Karna, S.K., et al., “Annihilation and Control of Chiral Domain Walls with Magnetic Fields”, Nano Letters 21 (3), 1205-1212 (2021).
6. Hall, R.M., et al, “Comparative study of the structural and magnetic properties of Mn1/3NbS2 and Cr1/3NbS2“, PRM 6, 024407 (2022).
7. Osorio, J., et al., “Chiral helimagnetism and stability of magnetic texturesin MnNb3S6”, PRB 108, 054414 (2023).
