Observation of magnetic skyrmion lattice in Cr$_{0.82}$Mn$_{0.18}$Ge by small-angle neutron scattering (2501.07162v1)

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.

• The paper reveals a robust skyrmion lattice in Cr0.82Mn0.18Ge stable at low magnetic fields (10–30 mT) and temperatures up to 6 K.
• The paper identifies a decreasing helical pitch from approximately 40 nm to 35 nm with cooling, reflecting strong anisotropic exchange interactions.
• The paper demonstrates a persistent metastable skyrmion phase at 2 K and zero field, highlighting its potential for spintronic applications.

Analysis of Magnetic Skyrmion Lattice in Cr$_{0.82}$Mn$_{0.18}$Ge using SANS

The paper entitled "Observation of magnetic skyrmion lattice in Cr$_{0.82}$Mn$_{0.18}$Ge by small-angle neutron scattering" presents an in-depth analysis of the magnetic properties of the B20-type chiral magnet Cr$_{0.82}$Mn$_{0.18}$Ge, focusing specifically on its skyrmion lattice (SkL) using small-angle neutron scattering (SANS). This paper contributes to the growing body of research on topological spin textures, which are crucial due to their potential applications in advanced spintronic devices.

Summary of Key Findings

The researchers conducted a thorough investigation of the magnetic phase diagram of Cr$_{0.82}$Mn$_{0.18}$Ge (0.82), revealing a detailed insight into the stabilization and characteristics of the skyrmion phase. The paper confirms that the skyrmion lattice is stable at low external magnetic fields ranging from 10 to 30 mT, over an extensive temperature range up to 6 K, markedly broad compared to other B20-type chiral magnets. A key observation is the gradual decrease in the helical pitch from approximately 40 nm to 35 nm as the system is cooled from its critical temperature (T₋C) down to 2 K, indicating an increase in the anisotropic exchange interaction at lower temperatures.

The SANS data provides crucial insights into the crystalline order of skyrmions by showing that 0.82 supports a two-dimensional hexagonal skyrmion lattice distinct from the three-dimensional hedgehog lattice observed in MnGe systems. Notably, the paper found that a metastable SkL persists at temperatures as low as 2 K, even at zero applied magnetic field, highlighting the robust nature of skyrmions in this compound.

Implications and Theoretical Contributions

This research enhances the understanding of magnetic textures in Cr-based B20 compounds and presents Cr$_{0.82}$Mn$_{0.18}$Ge as a promising material for further exploration in topological magnetism. The robust stability of the SkL at low temperatures and fields, coupled with its large temperature pocket, underscores this compound's potential for applications in magnetic storage devices and other information technology fields.

The findings also offer a new perspective on the interplay between exchange interactions and DMI in determining the characteristics of magnetic order within such systems. The significant decrease in the helical pitch with cooling suggests a prominent role of disorder-induced anisotropic exchange interactions, potentially linking to random anisotropy effects due to Cr and Mn concentration fluctuations.

Future Directions

The paper suggests several avenues for future research, including a deeper exploration of the role of magnetic frustration and exchange anisotropy in tuning skyrmion properties. A finer understanding of the metastability of skyrmions at zero field could open new design pathways for magnetic materials with desired skyrmion properties, fundamentally impacting the development of spintronic devices.

Further studies are recommended to explore the potential Weyl semimetal characteristics of Mn-doped CrGe compounds, proposing a unique platform for studying the interplay between electronic and magnetic topologies. Additionally, high-resolution techniques such as resonant small-angle X-ray scattering could elucidate anisotropic exchange contributions, further unraveling the complexity of spin textures in chiral magnets.

In summary, this paper contributes significantly to the understanding of magnetic skyrmions in B20 chiral magnets, offering insights that could inform the design of future magnetic materials and devices. Its detailed exploration of the skyrmion lattice in Cr$_{0.82}$Mn$_{0.18}$Ge reveals substantial possibilities for application and theoretical advancements in the field of condensed matter physics.