  Magnetic Weyl semimetals are predicted to host emergent electromagnetic
fields at heterogeneous strained phases or at the magnetic domain walls.
Tunability and control of the topological and magnetic properties is crucial
for revealing these phenomena, which are not well understood or fully realized
yet. Here, we use a scanning SQUID microscope to image spontaneous
magnetization and magnetic susceptibility of CeAlSi, a noncentrosymmetric
ferromagnetic Weyl semimetal candidate. We observe large metastable domains
alongside stable ferromagnetic domains. The metastable domains most likely
embody a type of frustrated or glassy magnetic phase, with excitations that may
be of an emergent and exotic nature. We find evidence that the heterogeneity of
the two types of domains arises from magnetoelastic or magnetostriction
effects. We show how these domains form, how they interact, and how they can be
manipulated or stabilized with estimated lattice strains on picometer levels.
CeAlSi is a frontier material for straintronics in correlated topological
systems.
