# Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe$_3$Sn

## TL;DR

This study investigates the magnetic properties of Fe$_3$Sn, revealing strong easy-plane anisotropy, vortex-domain patterns, and the influence of layer stacking on magnetic behavior, supported by experiments and ab initio calculations.

## Contribution

It provides new insights into the magnetic anisotropy and vortex-domain structures in Fe$_3$Sn, highlighting the role of layer stacking in tuning magnetic properties.

## Key findings

- Strong easy-plane uniaxial magnetic anisotropy increases at low temperature.
- Observation of micrometer-scale magnetic vortices with weak pinning.
- Theoretical calculations agree with experimental magnetic moments and anisotropy energy.

## Abstract

We report the structural and magnetic properties of high-quality bulk single crystals of the kagome ferromagnet Fe$_3$Sn. The dependence of magnetisation on the magnitude and orientation of the external field reveals strong easy-plane type uniaxial magnetic anisotropy, which shows a monotonous increase from $K_1=-0.99\times 10^6 J/m^3$ at 300\,K to $-1.23\times10^6 J/m^3$ at 2\,K. Our \textit{ab initio} electronic structure calculations yield the value of total magnetic moment of about 6.9 $\mu_B$/f.u. and a magnetocrystalline anisotropy energy density of 0.406\,meV/f.u. ($1.16\times10^6 J/m^3$) both being in good agreement with the experimental values. The self-consistent DFT computations for the components of the spin/orbital moments indicate that the small difference between the saturation magnetisations measured along and perpendicular to the kagome layers results from the subtle balance between the Fe and Sn spin/orbital moments on the different sites. In zero field, magnetic force microscopy reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at $\sim$3\,T applied perpendicular to the kagome plane. Our micromagnetic simulations, using the experimentally determined value of anisotropy, well reproduce the observed vortex-domain structure. The present study, in comparison with the easy-axis ferromagnet Fe$_3$Sn$_2$, shows that varying the stacking of kagome layers provides an efficient control over magnetic anisotropy in this family of Fe-based kagome magnets.