Magnetic properties of ferromagnetic nanoparticles of Fe x GeTe 2 ( x = 3, 5) directly exfoliated and dispersed in pure water.

Fe x GeTe 2 ( x = 3, 5) are two-dimensional ferromagnetic (FM) materials that have gained significant attention from researchers due to their relatively high Curie temperature and tunability. However, the methods for preparing FM nanoparticles (FNPs) and large-area Fe x GeTe 2 films are still in the early stages. Here, we studied the magnetic properties of Fe x GeTe 2 FNPs exfoliated via wet exfoliation in pure water. The coercive field of Fe 3 GeTe 2 FNPs increases significantly, up to 60 times, while that of Fe 5 GeTe 2 only slightly increases from that of bulk crystals. Further investigation related to the dimension of nanoparticles and the Henkel plot analysis reveals that the variation in their coercive field stems from the material's thickness-dependent coercive field and the type of term that governs the interaction between single-domain nanoparticles. Our work demonstrates a facile method for preparing FNPs using van der Waals FM materials and tuning their magnetic properties.