Shandite Co₃Sn₂S₂ has been synthesized and studied extensively, but there is still a lack of consensus regarding the magnetic ground state.  Since its discovery, it has been considered a ferromagnet with c-axis as its easy axis.  However, recently, there has been reports of exchange bias based on magnetometry and anomalous Hall effect attributed to spin glass and presence of antiferromagnetism at magnetic domains walls.  Separately, muon spin rotation has reported an antiferromagnetic phase coexisting with a ferromagnetic phase.  On the other hand, neutron scattering and non-linear optics experiments in Co₃Sn₂S₂ have not detected phase separation between antiferromagnetic and ferromagnetic phases and instead suggest a homogenous c-axis ferromagnetic phase or a canted c-axis ferromagnetic phase, respectively.   Conventional local probe techniques such as Magnetic Force Microscopy (MFM) and Magneto Optic Kerr Effect (MOKE) have not detected any antiferromagnetic phase either. Our own magnetic imaging studies using XMCD-PEEM and MOKE have not detected any antiferromagnetic phase either. On the other hand, they display unconventional magnetic domain patterns that may be associated to the unconventional magnetism in this material.

In addition, we employ an indirect local probe to investigate the magnetic phase of Co₃Sn₂S₂: spatially resolved Angular Resolved Photoemission Spectroscopy (ARPES) combined with Density Functional Theory (DFT) calculations.   Based on DFT calculations, the band structure of Co₃Sn₂S₂ is significantly different in the ferromagnetic vs antiferromagnetic phase.  By spatially mapping the local band structure, we discover small regions of the sample that match the antiferromagnetic band structure rather than the ferromagnetic band structure at 6 K(1).  This band converts to a band corresponding to the paramagnetic phase at 200 K, indicating that it is coupled to the magnetic phase.  

References 

1. S. A. Ekahana  et al. (arXiv:2401.15602, 2024).