In Weyl semimetals, chirality is a new degree of freedom that has great potential for fundamental physics as well as for the development of new devices for storing and processing information. The combination of the topology of the Weyl fermions with magnetism is particularly attractive: magnetic Weyl materials are predicted to exhibit electromagnetic properties transformed by emergent gauge axial fields. To advance this field of research, it is essential to understand the detailed magnetic domains physics of these materials. In this study, we investigated spontaneous magnetization and magnetic susceptibility of a non-centrosymmetric ferromagnetic (FM) Weyl semimetal: CeAlSi[1,2] . We utilized scanning SQUID susceptometer microscopy, which is regarded as a type of low-frequency and low-energy spectroscopic imaging technique. We observed large FM domains and discovered the coexistence of stable and metastable phases, which likely arise due to magnetostriction effects and are potentially highly tunable with small strains. The FM domain pattern is strongly correlated with both the magnitude and orientation of an external in-plane magnetic field. We demonstrate how these domains and heterogeneous phases can be fine-tuned and discuss the potential relationship between the magnetic domain walls and the novel loop Hall effect that our collaboration has discovered. The work presented here provides guidance for future investigations of the fundamental interplay between magnetism and exotic electromagnetism in Dirac systems.
 H.-Y. Yang et al., Phys. Rev. B, Editor's Choice Article, 103, 115143 (2021).
 B. Xu et al., Adv. Quantum Technol., Cover Article, 2000101 (2021).