Are Mn-intercalated transition metal dichalcogenides helimagnetic?

Mn-intercalated transition metal dichalcogenides (TMDs) are promising candidates for hosting helimagnetism, offering opportunities for next-generation spintronic applications. Despite their potential, key magnetic characteristics, including the intrinsic helix period, the critical magnetic field for phase transitions, and the role of shape anisotropy in modulating the spin textures, remain elusive. In this study, we investigate the helimagnetic properties of Mn1/3MX2 (M = Nb, Ta; X = S, Se) using first-principles calculations and micromagnetic simulations. Applying a rotation-state method, we extract the critical magnetic interaction parameters and successfully predict their helix periods, in agreement with experimental observations. By incorporating shape anisotropy into our theoretical framework, we elucidate its influence on spin configurations and clarify the distinct helimagnetic behaviors observed in bulk crystals and thin films. Furthermore, we propose a new approach to determine the critical magnetic field based on the slope of the magnetization curve in the low-field regime. Our results offer the first quantitative insights into the magnetic behavior of Mn-intercalated TMDs and establish a predictive framework for understanding helimagnetism in this emerging material class.