Topological spin/structure couplings in layered chiral magnet Cr _1/3 TaS ₂ : The discovery of spiral magnetic superstructure

Abstract

Chiral magnets have recently emerged as hosts for topological spin textures and related transport phenomena, which can find use in next-generation spintronic devices. The coupling between structural chirality and noncollinear magnetism is crucial for the stabilization of complex spin structures such as magnetic skyrmions. Most studies have been focused on the physical properties in homochiral states favored by crystal growth and the absence of long-ranged interactions between domains of opposite chirality. Therefore, effects of the high density of chiral domains and domain boundaries on magnetic states have been rarely explored so far. Herein, we report layered heterochiral Cr1/3TaS2, exhibiting numerous chiral domains forming topological defects and a nanometer-scale helimagnetic order interlocked with the structural chirality. Tuning the chiral domain density, we discovered a macroscopic topological magnetic texture inside each chiral domain that has an appearance of a spiral magnetic superstructure composed of quasiperiodic Néel domain walls. The spirality of this object can have either sign and is decoupled from the structural chirality. In weak, in-plane magnetic fields, it transforms into a nonspiral array of concentric ring domains. Numerical simulations suggest that this magnetic superstructure is stabilized by strains in the heterochiral state favoring noncollinear spins. Our results unveil topological structure/spin couplings in a wide range of different length scales and highly tunable spin textures in heterochiral magnets.

Structure and Magnetism of Iron- and Chromium-Intercalated Niobium and Tantalum Disulfides

“…Correlation between structural and magnetic domains in Cr 1/3 TaS 2 have been investigated using dark-field TEM and magnetic force microscopy (MFM). 107 Left-and righthanded structural domains forming six-valent graphs were observed, similar to those found in Fe 1/3 TaS 2 . 10 MFM measurements revealed correspondence between structural and mag- Lastly, we note that the value of T C for Cr 107 The value of T C may be sensitive to differences in stoichiometry or sample preparation conditions.…”

“…107 Left-and righthanded structural domains forming six-valent graphs were observed, similar to those found in Fe 1/3 TaS 2 . 10 MFM measurements revealed correspondence between structural and mag- Lastly, we note that the value of T C for Cr 107 The value of T C may be sensitive to differences in stoichiometry or sample preparation conditions. A promising direction for future studies could be examining relationships between disorder, growth conditions, and magnetic transitions in more detail.…”

“…This strengthens the DM interaction, resulting in shorter solitons, and increases MCAE, resulting in larger T C and critical field.As first reported by Parkin and Friend, Cr 1/3 TaS 2 exhibits magnetic ordering perpendicular to the c crystallographic axis like Cr 1/3 NbS 2 8,9. As with Cr 1/3 NbS 2 , the measured µ eff value of 3.78 µ B at saturation is consistent with the expected spin-only moment of Cr 3+ .The presence of CHM and CSL phases was confirmed in recent studies from Obeysekera et al, Zhang et al, and Du et al, which also examined the evolution of the magnetic phase diagram 19,26,107. Overall,Lorentz TEM and magnetotransport measurements reveal a qualitatively similar picture to Cr 1/3 NbS 2 : The CHM ground state is present below a certain transition temperature T C at low fields.…”

“…Overall,Lorentz TEM and magnetotransport measurements reveal a qualitatively similar picture to Cr 1/3 NbS 2 : The CHM ground state is present below a certain transition temperature T C at low fields. Upon applying higher H ⊥ c, a transition to a CSL state occurs, with the period of the CSL increasing with increasing H. Above the critical field, the material enters the FFM state.Lorentz TEM studies have also revealed direct evidence of the chiral spin textures in Cr 1/3 TaS 2 19,107. Similar to Cr 1/3 NbS 2 , stripe patterns with alternating areas of light and dark contrast are present in images taken without an external magnetic field at 94 K or 22 K, respectively.…”

“…Similar to Cr 1/3 NbS 2 , stripe patterns with alternating areas of light and dark contrast are present in images taken without an external magnetic field at 94 K or 22 K, respectively. Zhang et al observed a period of 25 nm,19 while Du et al observed a shorter period of 15 nm 107. This discrepancy may suggest differences in sample stoichiometry or homogeneity.…”