A high field magnetic force microscope for imaging air-sensitive materials

Imaging measurements of the intrinsic magnetic structures of air-sensitive materials have long posed significant technical challenges. Here, we present a novel magnetic force microscope (MFM) scanning head design that incorporates a rubber O-ring and a threaded sealing assembly to achieve independent, airtight encapsulation of the sample. The fully assembled scanning head exhibits a compact form factor, with an outer diameter of only 24 mm and a total length of merely 80 mm. Based on this design, we have constructed a MFM system tailored for imaging magnetic structures in air-sensitive materials. This MFM system enables operation at magnetic fields of up to 11.7 T and temperatures as low as 5 K. Using this system, we have successfully visualized the evolution of intrinsic magnetic domains in the air-sensitive material VI3 as a function of temperature and applied magnetic field at 5 K. In addition, twin domains arising from structural phase transitions are clearly resolved. Owing to its compact dimensions and high compatibility, the proposed MFM scanning head holds considerable potential for integration into higher-field setups, such as water-cooled bitter magnets, opening avenues for exploring magnetic structures of air-sensitive quantum materials under previously inaccessible experimental regimes.