  Topological materials featuring exotic band structures, unconventional
current flow patterns, and emergent organizing principles offer attractive
platforms for the development of next-generation transformative quantum
electronic technologies. The family of MnBi2Te4 (Bi2Te3)n materials is
naturally relevant in this context due to their nontrivial band topology,
tunable magnetism, and recently discovered extraordinary quantum transport
behaviors. Despite numerous pioneering studies, to date, the local magnetic
properties of MnBi2Te4 (Bi2Te3)n remain an open question, hindering a
comprehensive understanding of their fundamental material properties.
Exploiting nitrogen-vacancy (NV) centers in diamond, we report nanoscale
quantum imaging of magnetic phase transitions and spin fluctuations in
exfoliated MnBi2Te4 (Bi2Te3)n flakes, revealing the underlying spin transport
physics and magnetic domains at the nanoscale. Our results highlight the unique
advantage of NV centers in exploring the magnetic properties of emergent
quantum materials, opening new opportunities for investigating the interplay
between topology and magnetism.
