The milling profiles of single-crystal gallium nitride (GaN) when subjected to focused ion beams (FIBs) using gallium (Ga), xenon (Xe), and helium (He) ion sources were investigated. An experimental analysis via annular dark-field scanning transmission electron microscopy (ADF-STEM) and high-resolution transmission electron microscopy (HRTEM) revealed that Ga-FIB milling yields trenches with higher aspect ratios compared to Xe-FIB milling for the selected ion beam parameters (30 kV, 42 pA), while He-FIB induces local lattice disorder. Molecular dynamics (MD) simulations were employed to investigate the milling process, confirming that probe size critically influences trench aspect ratios. Interestingly, the MD simulations also showed that Xe-FIB generates higher aspect ratios than Ga-FIB with the same probe size, indicating that Xe-FIB could also be an effective option for nanoscale patterning. Atomic defects such as vacancies and interstitials in GaN from He-FIB milling were suggested by the MD simulations, supporting the lattice disorder observed via HRTEM. This combined experimental and simulation approach has enhanced our understanding of FIB milling dynamics and will benefit the fabrication of nanostructures via the FIB technique.

Iron borate (FeBO₃) has emerged as a promising candidate for magneto-optical applications owing to its unique combination of weak ferromagnetism (canted antiferromagnetic ordering) near room temperature and optical transparency in the visible range. While the growth of high-quality single crystals is well-established, the scalable synthesis of bulk polycrystalline FeBO₃ remains challenging, often hindered by the presence of impurity phases and inconsistent reproducibility. This work offers a comprehensive investigation into the synthesis of bulk FeBO₃ powder using combustion, solid-state, and flux growth approaches. The structural and magnetic properties of the resulting materials are compared, enabling a direct comparison of synthesis routes. Practical guidelines are provided for optimizing processing protocols to achieve phase-pure, highly reproducible FeBO₃, thereby advancing its integration into functional magneto-optical devices.