Aligned Fe3O4 magnetic nanoparticle films by magneto-electrospray method

Abstract

This work reports for the first time the preparation and evaluation of aligned Fe₃O₄ nanoparticle films via a magneto-electrospray method, i.e., electrospray under a magnetic field. The magnetic field was applied to align the magnetic moment of Fe₃O₄ particles. Well-dispersed Fe₃O₄ nanoparticles (NPs) with average sizes of 10, 25, and 45 nm were obtained using a bead-mill dispersion. The Fe₃O₄ nanoparticle slurries were mixed with a polyvinyl alcohol (PVA) solution and then deposited on Si-wafers under a 0.1 T magnetic field. The Fe₃O₄ crystalline structures were maintained after both dispersion and deposition, as characterized by X-ray diffraction patterns. Hysteresis curves revealed that the magnetic coercivity (H_c) of the well-dispersed nanoparticle slurries decreased owing to magnetic interactions among particles. However, the H_c values of the films were larger than those of the nanoparticle slurries. The values further increased from the application of a magnetic field during film deposition. This enhancement was attributed to alignment of the magnetic moments of the Fe₃O₄ NPs. These results show that tuning of the magnetic properties of materials, such as Fe₃O₄ NPs, can be achieved by controlling the alignment of their magnetic moment.