Isotropic Nature of the Metallic Kagome Ferromagnet Fe3Sn2 at High Temperatures.

Rebecca L Dally,Nirmal J Ghimire,Jeffrey W Lynn,Nicholas Bishop,Daniel Phelan

doi:10.3390/cryst11030307

Abstract

Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe3Sn2 is an isotropic ferromagnet below to at least 480 K - the lower temperature threshold of our experimental configuration. Fe3Sn2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at elevated temperatures, there is an absence of magnetocrystalline anisotropy and that the system behaves as a typical exchange ferromagnet with a spin stiffness .

Highlights

The temperature renormalization of the spin stiffness for Heisenberg ferromagnets is expected to follow a power law on approach to TC with the critical exponents ν − β = 0.34 [36], which is the exponent found in this study, further showing that magnetically, Fe3 Sn2 is a typical exchange ferromagnet at elevated temperatures
We remark that the TC of 631 K for Ni is comparable to Fe3 Sn2, but the spin stiffness of D = 550 meV Å2 in the ground state of this itinerant magnet is much larger [39]
The value of D ( T = 0 K) = 231 ± 7 meV Å2 using the Dyson formalism is a better estimate of the ground state spin stiffness, the limited temperature range accessible in this study still results in a large extrapolation window

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The two-dimensional kagome lattice lends itself to hosting a variety of phenomena depending on the chemical species occupying the network of corner-sharing triangles. The tight-binding model for itinerant electrons leads to an electronic spectrum with a flat band and two Dirac crossings at the symmetry protected K and K 0 corner points of the hexagonal Brillouin zone. Chemical tuning can drive the Fermi level to meet the

Methods

Results

Conclusion