Paper

NMR study of the local magnetic order in the kagome Weyl semimetal Co\\(_3\\)Sn\\(_2\\)S\\(_2\\)

Mukhamedshin, Irek, Wzietek, Pawel, Brouet, Véronique, get, Anne, Mendels, Philippe, Colson, Dorothée, Bert, Fabrice

2024

Overview

A magnetic Weyl semimetal presents the intriguing possibility of controlling topological properties through magnetic order. The kagome compound ~has emerged as one of the most thoroughly characterized magnetic Weyl semimetals, yet the potential coexistence of a ferromagnetic state below \\(T_c\\) = 172~K with a non-collinear antiferromagnetic phase or a glassy state remains unresolved. We employ \\(^59\\)Co NMR to gain a local perspective on the magnetic order. The magnetic and electric field gradient tensors at room temperature are determined by fitting the NMR spectra using evolutionary algorithms. Zero-field NMR measurements reveal that all Co sites are equivalent in the magnetic phase at low temperatures and up to 90~K. The local magnetic field follows in intensity the macroscopic magnetization as a function of temperature and is tilted from the c-axis by a few degrees toward the nearest triangle center. Above 90~K, a shoulder appears on the low-field side, which we attribute to a preferential tilting of the local field in one direction, breaking the equivalence between the three Co sites of the kagome structure. We rule out any coexistence with an in-plane antiferromagnetic phase and suggest instead that in-plane ferromagnetic-like moments appear above 90~K and play an increasing role in the magnetic order up to the magnetic transition.

• Publisher: Cornell University Library, arXiv.org
• Subject: Antiferromagnetism / Electric fields / Equivalence / Evolutionary algorithms / Ferromagnetism / Low temperature / Magnetic properties / Magnetic transitions / NMR / Nuclear magnetic resonance / Room temperature / Tensors