Spin eigenexcitations of an antiferromagnetic skyrmion

Abstract

We theoretically predict and classify the localized modes of a skyrmion in a collinear uniaxial antiferromagnet and discuss how they can be excited. As a central result we find two branches of skyrmion eigenmodes with distinct physical properties characterized by being low or high energy excitations. The frequency dependence of the low-energy modes scales as R −2 0 for skyrmions with large radius R0. Furthermore, we predict localized high-energy eigenmodes, which have no direct ferromagnetic counterpart. Except for the breathing mode, we find that all localized antiferromagnet skyrmion modes, both in the low and high-energy branch, are doubly degenerated in the absence of a magnetic field and split otherwise. We explain our numerical results for the low-energy modes within a string model representing the skyrmion boundary. arXiv:1902.09846v1 [cond-mat.str-el]

Boundary conditions for the Néel order parameter in a chiral antiferromagnetic slab

“…Even for ferromagnets, a rigorous description of skyrmions of small [61] and large [62] radius is a complicated task, which is usually addressed by asymptotic analysis or numerically. Often, models of circular domain walls or numerical integration are utilized, which allows to explain current-driven dynamics [9,39,63] and excitations [64]. To address a 3D skyrmion texture, we describe them qualitatively using an axially symmetric Ansatz θ = θ(r, z) and φ = φ(χ, z).…”

“…Large radius skyrmions in bulk samples can be described as circular domain walls using the Ansatz [64] cos…”

Stability of skyrmion crystal phase in antiferromagnetic triangular lattice with DMI and single-ion anisotropy

“…In recent years the interest shifted from the ferromagnets (FM), where the skyrmions were initially found [6], to new potentially skyrmion-hosting materials. For instance, high expectations are put on antiferromagnetic (AFM) materials [7,8], implementation of which in skyrmion-based devices is reported to have certain advantages over the FM ones [9,10]. Among other mechanisms, which can lead to the stabilization of a skyrmion phase in bulk samples and thin films [11][12][13], is the inversion-symmetrybreaking Dzyaloshinskii-Moriya interaction, responsible for the creation of both Néeland Bloch-type skyrmions of the size of 5-100 nm with fixed helicity.…”

Coupled skyrmion breathing modes in synthetic ferri- and antiferromagnets

“…Even though in Ref. [27] the spin eigenexcitations of a skyrmion in a collinear uniaxial antiferromagnetic thin film were investigated by means of numerical and analytical methods, the dynamic behavior is expected to be different in synthetic AFMs, where the interlayer exchange coupling is much weaker than the direct exchange in crystalline AFMs. In other words, there is a stronger separation of the two magnetic subsystems in synthetic AFMs, which also implies the presence of small dipolar fields [7,28].…”