Biquadratic exchange interactions in two-dimensional magnets

Magnetism in recently discovered van der Waals materials has opened several avenues in the study of fundamental spin interactions in truly two-dimensions.A paramount question is what effect higher-order interactions beyond bilinear Heisenberg exchange have on the magnetic properties of few-atom thick compounds.Here we demonstrate that biquadratic exchange interactions,which is the simplest and most natural form of non-Heisenberg coupling,assume a key role in the magnetic properties of layered magnets.Using a combination of nonperturbative analytical techniques,non-collinear first-principles methods and classical Monte Carlo calculations that incorporate higher-order exchange,we show that several quantities including magnetic anisotropies,spin-wave gaps and topological spin-excitations are intrinsically renormalized leading to further thermal stability of the layers.

Relativistic domain-wall dynamics in van der Waals antiferromagnet MnPS_(3)

The discovery of two-dimensional(2D)magnetic van der Waals(vdW)materials has flourished an endeavor for fundamental problems as well as potential applications in computing,sensing and storage technologies.Of particular interest are antiferromagnets,which due to their intrinsic exchange coupling show several advantages in relation to ferromagnets such as robustness against external magnetic perturbations.Here we show that,despite of this cornerstone,the magnetic domains of recently discovered 2D vdW MnPS_(3)antiferromagnet can be controlled via magnetic fields and electric currents.We achieve ultrafast domain-wall dynamics with velocities up to~3000 m s^(−1)within a relativistic kinematic.Lorentz contraction and emission of spin-waves in the terahertz gap are observed with dependence on the edge termination of the layers.Our results indicate that the implementation of 2D antiferromagnets in real applications can be further controlled through edge engineering which sets functional characteristics for ultrathin device platforms with relativistic features.

Bimeron clusters in chiral antiferromagnets

A magnetic bimeron is an in-plane topological counterpart of a magnetic skyrmion.Despite the topological equivalence,their statics and dynamics could be distinct,making them attractive from the perspectives of both physics and spintronic applications.In this work,we demonstrate the stabilization of bimeron solitons and clusters in the antiferromagnetic(AFM)thin film with interfacial Dzyaloshinskii–Moriya interaction(DMI).Bimerons demonstrate high current-driven mobility as generic AFM solitons,while featuring anisotropic and relativistic dynamics excited by currents with in-plane and out-ofplane polarizations,respectively.Moreover,these spin textures can absorb other bimeron solitons or clusters along the translational direction to acquire a wide range of Néel topological numbers.The clustering involves the rearrangement of topological structures,and gives rise to remarkable changes in static and dynamical properties.The merits of AFM bimeron clusters reveal a potential path to unify multibit data creation,transmission,storage,and even topology-based computation within the same material system,and may stimulate spintronic devices enabling innovative paradigms of data manipulations.