Annihilation and Control of Chiral Domain Walls with Magnetic Fields

Abstract

The control of domain walls is central to nearly all magnetic technologies, particularly for information storage and spintronics. Creative attempts to increase storage density need to overcome volatility due to thermal fluctuations of nanoscopic domains and heating limitations. Topological defects, such as solitons, skyrmions, and merons, may be much less susceptible to fluctuations, owing to topological constraints, while also being controllable with low current densities. Here, we present the first evidence for soliton/soliton and soliton/antisoliton domain walls in the hexagonal chiral magnet Mn 1/3 NbS 2 that respond asymmetrically to magnetic fields and exhibit pair-annihilation. This is important because it suggests the possibility of controlling the occurrence of soliton pairs and the use of small fields or small currents to control nanoscopic magnetic domains. Specifically, our data suggest that either soliton/soliton or soliton/antisoliton pairs can be stabilized by tuning the balance between intrinsic exchange interactions and long-range magnetostatics in restricted geometries.

Comparative study of the structural and magnetic properties of Mn1/3NbS2 and Cr1/Hall1, Loudon2, Midgley3 et al. 2022Phys. Rev. Materials13180View full textAdd to dashboardCite

“…The form of the boundary between phase II and the FMM phase matches qualitatively with the boundary shown in Ref. [27], albeit, as noted above, at lower fields.…”

“…These data correspond well with our ac susceptibility measurements, with clear features in dM/dH marking potential phase boundaries. The M(H ) curves shown here differ in several important respects from those reported earlier [26][27][28], as discussed in the Supplemental Material [35].…”

“…These features are not seen in similar data collected for our crystals. Reference [27] proposed a helical phase at low field and low temperature, separated from a nearly ferromagnetic phase at higher temperatures by an almost vertical phase boundary at ∼20 K that coincides with the disappearance of hysteresis in the M(H ) curves. Our measurements provide no evidence for such a phase boundary below 20 K in these crystals of Mn 1/3 NbS 2 , although there is a significant increase in the losses in phase I, reflected by an increase in χ (T ), as the ac measuring frequency increases (see Supplemental Material [35]).…”

“…A combination of powder neutron diffraction and heatcapacity measurements have been used to suggest a change in the magnetic ordering in the material below 20 K. A magnetic field-temperature phase diagram constructed from hysteresis in magnetization measurements suggests that Mn 1/3 NbS 2 might be helimagnetic at temperatures under 20 K [27]. Recent Lorentz transmission electron microscopy (LTEM) measurements of Mn 1/3 NbS 2 [27] were used to support this conclusion. The 3D Heisenberg model has been applied to Mn 1/3 NbS 2 and the magnetic moments were found to be short range and isotropic, allowing for coupling both within the ab plane and to the c axis [28].…”

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

“…[ 34 ] Certain reports have claimed the observation of helical magnetic structures and solitons in Mn 1/3 NbS 2 with the magnetic helix having a long pitch period of ≈250 nm. [ 35,36 ] A smaller spatial period could lead to a smaller device size and higher storage density in future memory devices.…”