Observation of magnetic skyrmion lattice in Cr$_{0.82}$Mn$_{0.18}$Ge by small-angle neutron scattering

TL;DR

This study uses small-angle neutron scattering to confirm the presence of a stable skyrmion lattice in Cr$_{0.82}$Mn$_{0.18}$Ge, revealing its magnetic phase diagram and unique properties over a wide temperature range.

Contribution

First comprehensive SANS analysis demonstrating skyrmion lattice stabilization in Cr$_{0.82}$Mn$_{0.18}$Ge and detailing its magnetic phase diagram and textures.

Findings

Skyrmion phase stable at 10-30 mT magnetic fields

Wide temperature stability range of skyrmions (~6 K)

Persistence of metastable skyrmions at zero field at 2 K

Abstract

Incommensurate magnetic phases in chiral cubic crystals are an established source of topological spin textures such as skyrmion and hedgehog lattices, with potential applications in spintronics and information storage. We report a comprehensive small-angle neutron scattering (SANS) study on the $B20$-type chiral magnet Cr$_{0.82}$Mn$_{0.18}$Ge, exploring its magnetic phase diagram and confirming the stabilization of a skyrmion lattice under low magnetic fields. Our results reveal a helical ground state with a decreasing pitch from 40 nm to 35 nm upon cooling, and a skyrmion phase stable in applied magnetic fields of 10-30 mT, and over an unusually wide temperature range for chiral magnets of 6 K ($\sim T_\textrm{C}/2 < T < T_\textrm{C}$, $T_\textrm{C}=13$ K). The skyrmion lattice forms a standard two-dimensional hexagonal coordination that can be trained into a single domain, distinguishing it from the three-dimensional hedgehog lattice observed in MnGe-based systems. Additionally, we demonstrate the persistence of a metastable SkL at 2 K, even at zero field. These findings advance our understanding of magnetic textures in Cr-based $B20$ compounds, highlighting Cr$_{0.82}$Mn$_{0.18}$Ge~as a promising material for further exploration in topological magnetism.