Study of depth and polarization dependence of a novel surface-spiral-state in a cubic chiral insulator magnet

The ground-state helical magnetic structures of cubic chiral systems are well-explained by the Bak-Jensen model that considers the interplay between Heisenberg exchange interaction, antisymmetric Dzyaloshinskii- Moriya interaction (DMI), anisotropic exchange interaction (AEI), and cubic anisotropy. The weak cubic anisotropy determines the spin-wave gap and some additional peculiarities of the helix axis orientation under a magnetic field, while the exchange, DMI and AEI are responsible for the helical spiral and its orientation relative to crystal axes. The latter interaction is often neglected due to its weak impact on experimental observations. However, the cubic and exchange anisotropies are important for defining the propagation direction of the helix, and ultimately the orientation of any field-induced skyrmion lattice (SkL) in these materials. In an attempt to study the field-induced first-order transformation between the helical and conical state (Proposal number: 2021024923), we have uncovered a novel magnetic phase, which lies on the borderline between these two well-defined states. Determination of the exact structure of this state will have impactful consequences in the physics of skyrmions and related fields.