Formation and stability of metastable skyrmionic spin structures with various topologies in an ultrathin film

TL;DR

This study uses spin dynamics simulations to explore the formation and stability of various metastable skyrmionic spin structures with different topologies in an ultrathin film, highlighting the roles of exchange frustration and Dzyaloshinsky--Moriya interaction.

Contribution

It demonstrates the creation of diverse metastable skyrmionic structures with topological charges from -3 to 2 in a specific bilayer system, emphasizing the influence of exchange frustration and surface-induced Dzyaloshinsky--Moriya interaction.

Findings

Metastable skyrmionic structures with topological charges from -3 to 2 observed.

Exchange frustration is key to creating various skyrmionic topologies.

Dzyaloshinsky--Moriya interaction favors Q=-1 skyrmions and influences shape and orientation.

Abstract

We observe metastable localized spin configurations with topological charges ranging from $Q=-3$ to $Q=2$ in a (Pt$_{0.95}$Ir$_{0.05}$)/Fe bilayer on Pd$(111)$ surface by performing spin dynamics simulations, using a classical Hamiltonian parametrized by ab initio calculations. We demonstrate that the frustration of the isotropic exchange interactions is responsible for the creation of these various types of skyrmionic structures. The Dzyaloshinsky--Moriya interaction present due to the breaking of inversion symmetry at the surface energetically favors skyrmions with $Q=-1$, distorts the shape of the other objects, and defines a preferred orientation for them with respect to the underlying lattice.