Field-induced condensation of $\pi$ to 2$\pi$ soliton lattices in chiral magnets

TL;DR

This study observes a tunable transition from $bc$ to 2$bc$ soliton lattices in a chiral magnet, revealing the microscopic mechanisms and broad relevance for spintronic applications.

Contribution

It provides the first direct observation and microscopic understanding of $bc$ to 2$bc$ soliton lattice transition in a non-centrosymmetric Heusler compound.

Findings

Identified $bc$-CSL as the magnetic ground state.

Observed transition to 2$bc$-CSL under magnetic fields.

Demonstrated the role of anisotropy and magnetostatic interactions.

Abstract

Chiral soliton lattices (CSLs) are nontrivial spin textures that emerge from the competition between Dzyaloshinskii-Moriya interaction, anisotropy, and magnetic fields. While well established in monoaxial helimagnets, their role in materials with anisotropic, direction-dependent chirality remains poorly understood. Here, we report the direct observation of a tunable transition from $\pi$ to 2$\pi$ soliton lattices in the non-centrosymmetric Heusler compound Mn1.4PtSn. Using Lorentz transmission electron microscopy, resonant elastic X-ray scattering, and micromagnetic simulations, we identify a $\pi$-CSL as the magnetic ground state, in contrast to the expected helical phase, which evolves into a classical 2$\pi$-CSL under increasing out-of-plane magnetic fields. This transition is governed by a delicate interplay between uniaxial magnetocrystalline anisotropy and magnetostatic interactions, as captured by a double sine-Gordon model. Our analysis not only reveals the microscopic mechanisms stabilizing these soliton lattices but also demonstrates their general relevance to materials with D2d, S4, Cnv, or Cn symmetries. The results establish a broadly applicable framework for understanding magnetic phase diagrams in chiral systems, with implications for soliton-based spintronic devices and topological transport phenomena.