Magnetic nanoparticles are of significant importance due to their potential applications in the fields of science, engineering and nanomedicine. Using the Langmuir-Blodgett technique, 2D assemblies of Fe3O4 nanoparticles were deposited on solid substrates at various surface pressures with and without an external magnetic field. Chain like and nanodomain structures were observed in LB monolayers. Shape deformation and aggregation of chains were investigated under lateral pressure and external magnetic field. Field Emission Scanning Electron Microscopy micrographs showed the formation of magnetic nanodomains and deformation of chains under mechanical compression. For the first time, we report the formation of magnetic nanodomains in LB films and their successful transformation to a glass substrate. This research provides fundamental insights into the formation of magnetic films under both dipole–dipole interactions and mechanical compression, which is very important for experimental and applied research. Furthermore, vast LB films of closely packed nanoparticles were prepared. The present study demonstrated that the presence of an external magnetic field improves the quality of LB films of closely packed nanoparticles. The effect of an external at smaller surface pressures was to convert nanodomains and chains into striped structures.
