Static and dynamic properties of bimerons in a frustrated ferromagnetic monolayer

Abstract

Magnetic bimeron is a topological counterpart of skyrmions in in-plane magnets, which can be used as spintronic information carrier. We report the static properties of bimerons with different topological structures in a frustrated ferromagnetic monolayer, where the bimeron structure is characterized by the vorticity Qv and helicity η. It is found that the bimeron energy increases with Qv, and the energy of an isolated bimeron with Qv = ±1 depends on η. We also report the dynamics of frustrated bimerons driven by the spin-orbit torques, which depend on the strength of the damping-like and field-like torques. We find that the isolated bimeron with Qv = ±1 can be driven into linear or elliptical motion when the spin polarization is perpendicular to the easy axis. We numerically reveal the damping dependence of the bimeron Hall angle driven by the damping-like torque. Besides, the isolated bimeron with Qv = ±1 can be driven into rotation by the damping-like torque when the spin polarization is parallel to the easy axis. The rotation frequency is proportional to the driving current density. In addition, we numerically demonstrate the possibility of creating a bimeron state with a higher or lower topological charge by the current-driven collision and merging of bimeron states with different Qv. Our results could be useful for understanding the bimeron physics in frustrated magnets.

Meron-like topological spin defects in monolayer CrCl3

“…As indicated in Fig. 3(a, d) , some pairs of vortex/antivortex type merons are found to be anti-parallelly aligned with each other at low temperature, forming “quadrupole-like” topological excitations 57 , 60 . The presence of these hierarchical excitations indicates that, although the classical MC treatment does not take into account the quantum nature of spins, it does include the correlations of magnetic moments from the Heisenberg model 9 .…”

“…Particularly, because of the pairing character of these topological spin defects, it is expected that doped free carriers could be intrinsically spin-polarized, and the transport of charged meron pairs might be dispersionless at low temperature [54][55][56] . Although those dynamic behaviors and quantitative interactions between merons are beyond the scope of this study, they would be interesting topics for future studies [57][58][59] . Beyond meron pairs, our MC simulations reveal more complicated spin textures, such as the higher-order states involved more than two merons.…”

Topological structures, spontaneous symmetry breaking and energy spectra in dipole hexagonal lattices

“…These structures are found in a variety of magnetic materials 25 – 34 , and are potentially interesting for information processing and data storage. As opposed to the classic interaction energy functional form ( 2 ), the Hamiltonian for quantum spins, running over nearest-neighbor, next-nearest-neighbor, and next-next-nearest-neighbor sites, contains additional non-linear terms that are responsible for the appearance of magnetic skyrmions in 3D or magnetic bimerons in 2D 35 . Also, these topological magnetized spin textures carry integer topological charges Q .…”

Nonreciprocal dynamics of ferrimagnetic bimerons

“…Different types of topological spin textures have been investigated for a few decades, such as domain walls [17,18], skyrmions [12,19,20] and bimerons [21][22][23][24][25][26][27][28][29][30][31], which emerge in ferromagnetic (FM) [17,19,25], ferrimagnetic (FiM) [32][33][34][35] and antiferromagnetic (AFM) [18,36,37] materials. In particular, FM skyrmions are promising as nonvolatile information carriers to serve the future memory and logic computing devices [38][39][40][41][42][43][44].…”

“…Recently, FiM materials have received great attention, since the AFM spin dynamics is realized in ferrimagnets at the angular momentum compensation point [33,51] and unlike the antiferromagnet, even for compensated ferrimagnet, we can detect the magnetization of one sublattice using magnetotransport measurements, such as anomalous Hall effect or tunnel magnetoresistance. On the other hand, a magnetic bimeron consisting of two merons is considered as the topological counterpart of a magnetic skyrmion in in-plane magnets and is stabilized in various magnetic materials [22,24,[26][27][28][29][30][31]. Recent reports show that two-dimensional CrCl 3 [52,53] and van der Waals LaCl/In 2 Se 3 heterostructures [54] are promising candidates for hosting bimerons.…”