Disorder-resilient transition of Helical to Conical ground states in M$_{1/3}$NbS$_2$, M=Cr,Mn

TL;DR

This study investigates the magnetic states of Cr$_{1/3}$NbS$_2$ and Mn$_{1/3}$NbS$_2$, revealing disorder-resilient chiral helimagnetism and providing insights into their magnetic phase transitions using NMR and density functional calculations.

Contribution

It provides the first comprehensive NMR and computational analysis confirming chiral helimagnetism in Mn$_{1/3}$NbS$_2$, despite higher defect densities.

Findings

Cr$_{1/3}$NbS$_2$ exhibits textbook chiral helimagnetism signatures.

Mn$_{1/3}$NbS$_2$ also shows chiral helimagnetism despite defects.

Large critical field (~5 T) observed for Mn compound's ferromagnetic phase.

Abstract

The discovery of chiral helical magnetism (CHM) in Cr$_{1/3}$NbS$_2$ and the stabilization of a chiral soliton lattice (CSL) has attracted considerable interest in view of their potential technological applications. However, there is an ongoing debate regarding whether the sister compound, Mn$_{1/3}$NbS$_2$, which shares the same crystal structure, exhibits similar nontrivial properties which rely on the stabilization of the lack of inversion symmetry at the magnetic ion. In this study, we conduct a comprehensive investigation of the magnetically ordered states of both compounds, using $^{53}$Cr, $^{55}$Mn and $^{93}$Nb nuclear magnetic resonance. Our results, supported by density functional calculations, detect in a high-quality single crystal of Cr$_{1/3}$NbS$_2$ all the signatures of the monoaxial CHM in a magnetic field, identifying it as a textbook NMR case. The detailed understanding of this prototypic behavior provides a reference for Mn$_{1/3}$NbS$_2$. Despite the much larger density of specific defects in this second single crystal, we confirm the presence of a CHM phase in the Mn compound, characterized by a very large critical field for the forced ferromagnetic phase ($\approx 5$ T for H$\parallel\hat c$).