Chiral Helimagnetism and One-Dimensional Magnetic Solitons in a Cr-Intercalated Transition Metal Dichalcogenide.

Chenhui Zhang ,Chi Young Song ,Yong Peng ,Yan Wen ,Chen Liu ,Z Q Qiu ,Bojian Zhou ,Ye Yuan ,Udo Schwingenschlögl ,Wenbo Mi ,Yongjiu Lei ,Husam N Alshareef ,Zhi Jiang ,Senfu Zhang ,Peng Li ,Junwei Zhang ,Dongxing Zheng ,Aurélien Manchon ,Zhipeng Hou ,Xixiang Zhang

doi:10.1002/adma.202101131

Abstract

Chiral magnets endowed with topological spin textures are expected to have promising applications in next-generation magnetic memories. In contrast to the well-studied 2D or 3D magnetic skyrmions, the authors report the discovery of 1D nontrivial magnetic solitons in a transition metal dichalcogenide 2H-TaS2 via precise intercalation of Cr elements. In the synthetic Cr1/3 TaS2 (CTS) single crystal, the coupling of the strong spin-orbit interaction from TaS2 and the chiral arrangement of the magnetic Cr ions evoke a robust Dzyaloshinskii-Moriya interaction. A magnetic helix having a short spatial period of ≈25nm is observed in CTS via Lorentz transmission electron microscopy. In a magnetic field perpendicular to the helical axis, the helical spin structure transforms into a chiral soliton lattice (CSL) with the spin structure evolution being consistent with the chiral sine-Gordon theory, which opens promising perspectives for the application of CSL to fast-speed nonvolatile magnetic memories. This work introduces a new paradigm to soliton physics and provides an effective strategy for seeking novel 2D magnets.

Highlights

Chiral spin textures are typically discovered in noncentrosymmetric systems and are stabilized due to the competition between exchange interaction, magnetic anisotropy, and Dzyaloshinskii–Moriya (DM) interaction.[1,2] They are expected to be promising candidates for the fabrication of novel magnetic memories that integrate high storage density, fast processing speed, and low energy consumption.[3,4] Van der Waals materials have stable crystal structures even down to atomic thickness and show great compatibility for assembling artificial heterostructures,[5] rendering them as ideal platforms for developing such memories
The temperature-dependent resistance reduces rapidly below ≈140 K. Because this temperature is approximately similar to the magnetic phase transition temperature (Tc discussed ) of CTS, the sharp decrease in resistance at ≈140 K probably correlates with the onset of spin ordering, which suppresses electron scattering
The contrast pattern in the high-field region shown in Figure 3e can be well-interpreted by the formation of the chiral soliton lattice (CSL) state: the wide gray stripes correspond to the ferromagnetic domains, while the narrow dark stripes correspond to the left-handed magnetic solitons.[20]

Summary

Introduction

Chiral spin textures are typically discovered in noncentrosymmetric systems and are stabilized due to the competition between exchange interaction, magnetic anisotropy, and Dzyaloshinskii–Moriya (DM) interaction.[1,2] They are expected to be promising candidates for the fabrication of novel magnetic memories that integrate high storage density, fast processing speed, and low energy consumption.[3,4] Van der Waals (vdW) materials have stable crystal structures even down to atomic thickness and show great compatibility for assembling artificial heterostructures,[5] rendering them as ideal platforms for developing such memories. The chiral soliton lattice (CSL) is defined as the superlattice of solitons and ferromagnetic domains.[20] As a particle-like excitation, the dynamic control of solitons, including creation, annihilation, and motion, are expected to be realized via the application of a spin-polarized current.[25,26] More importantly, by comparing the Klirr factors (the ratio of the third- to first-harmonic ac magnetic response) of various non-collinear spin textures, a recent study pointed out that the CSL exhibits stronger robustness of the spin texture against the external magnetic field than the skyrmion lattice.[27] This provides a reasonable explanation for the fact that the CSL can survive in very wide temperature and field ranges in the phase diagram,[28,29,30] which is essential for practical applications Another important parameter for the fabrication of practical devices is the spatial size of the spin textures. Endowed with the exotic features, CTS is expected to be a new paradigm for the soliton physics and low-dimensional spintronic applications

Crystal Structure and Transport Properties

Evidence of Chiral Soliton Lattice Exhibited in Magnetic Properties

Phase Diagram

Conclusion

Experimental Section

Data Availability Statement