by Magnetic Force Microscopy*

Ferromagnetic Weyl semimetal Co₃Sn₂S₂, within which Co atoms form a quasi-2D Kagomé lattice, has attracted great attention because novel phenomena such as quantum anomalous Hall effect can emerge as the results of the interplay between topology and magnetism. While the existence of Weyl points and Fermi arcs have been realized in the ferromagnetic state at low temperature [1-2], an anomalous magnetic phase (A-phase) revealed by low-field magnetization, AC susceptibility [3] and transport [4] measurements slightly below its Curie temperature remain unsolved. Skyrmion phase [3], spin glass [5], co-existence of out-of-plane ferromagnetic and in-plane antiferromagnetic order [6], and a 2D phase transition within the domain walls [7] have been proposed. Here, we conducted comprehensive magnetic imaging study on Co₃Sn₂S₂ single crystals by using variable temperature magnetic force microscopy (MFM) across the A-phase. Our temperature dependent and magnetic field dependent MFM images, consistent with a recent Lorentz microscopy study [8], demonstrate the important role of magnetic bubble domain formation and the magnetic domain wall motion in the A-phase.

References:

[1] Liu et al., Science 365, 1282–1285 (2019).

[2] Morali et al., Science 365, 1286–1291 (2019).

[3] Kassem et al., PRB 96, 014429 (2017).

[4] Lachman et al., Nat. Commun. 11, 560 (2020).

[5] Lachman et al., Nat. Commun. 11, 560 (2020).

[6] Guguchia et al., Nat. Commun. 11, 559 (2020).

[7] Lee et al., Nat Commun 13, 3000 (2022).

[8] Sugawara et al., Phys. Rev. Materials 3, 104421 (2019).