Magnetic and geometric control of spin textures in the itinerant kagome magnet Fe3Sn2

Markus Altthaler,Stephan Krohns,Dennis Meier,István Kézsmárki,Vladimir Tsurkan,Erik Roede,Erik Lysne,Hiroyuki Nakamura,Mohamed A Kassem,Lilian Prodan

doi:10.1103/physrevresearch.3.043191

Abstract

Magnetic materials with competing magnetocrystalline anisotropy and dipolar energies can develop a wide range of domain patterns, including classical stripe domains, domain branching, and topologically trivial and nontrivial (skyrmionic) bubbles. We image the magnetic domain pattern of ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$ by magnetic force microscopy and study its evolution due to geometrical confinement, magnetic fields, and their combination. In ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$ lamellae thinner than 3 $\ensuremath{\mu}\mathrm{m}$, we observe stripe domains whose size scales with the square root of the lamella thickness, exhibiting classical Kittel scaling. Magnetic fields turn these stripes into a highly disordered bubble lattice. Complementary micromagnetic simulations quantitatively capture the magnetic field and thickness dependence of the magnetic patterns, reveal strong reconstructions of the patterns between the surface and the core of the lamellae, and identify the observed bubbles as skyrmionic bubbles. Our results imply that geometrical confinement together with competing magnetic interactions can provide a path to fine-tune and stabilize different types of topologically trivial and nontrivial spin structures in centrosymmetric magnets.

Highlights

Progress in information and communication technology is driven by the discovery of new materials and phenomena that enable components with improved functionality
We study how variable magnetic fields transform the magnetic stripe domains into skyrmionic bubbles while keeping the sample thickness fixed and, vice versa, how the magnetic structure evolves as the sample thickness varies under constant magnetic field
The magnetic force microscopy (MFM) measurements are complemented by micromagnetic simulation of the three-dimensional (3D) magnetic order and its response to the applied manipulations, providing additional insight into the nanoscale physics of topological spin textures in magnetic materials with competing uniaxial and shape anisotropies

Summary

INTRODUCTION

Progress in information and communication technology is driven by the discovery of new materials and phenomena that enable components with improved functionality. Depending on the relative magnitudes of the involved interactions, topologically trivial and nontrivial bubbles can coexist, leading to complex mixed states [18,25] For achieving such exotic magnetic states and, novel functional responses, materials with comparable values of perpendicular uniaxial magnetocrystalline anisotropy (PMA) and shape anisotropy are promising [18,26]. We study the kagome crystal Fe3Sn2, i.e., an itinerant ferromagnet with competing uniaxial (Ku) and shape anisotropies [27] The latter is described by the quality factor Q = 2Ku/μ0Ms2at, which has a value of about 0.15. The MFM measurements are complemented by micromagnetic simulation of the three-dimensional (3D) magnetic order and its response to the applied manipulations, providing additional insight into the nanoscale physics of topological spin textures in magnetic materials with competing uniaxial and shape anisotropies

Crystal growth

Lamella preparation

Magnetic imaging

Micromagnetic simulations

RESULTS