The influence of magnetic interactions and shape anisotropy on the alignment and assembly of BaFe12O19 and Er2O3 nanoplates

Abstract

Magnetically anisotropic material with useful properties can be obtained when the barium ferrite (BaFe12O19) plates are aligned in a single plane. We studied the influence of the magnetic forces and the shape anisotropy on the alignment of barium ferrite nanoparticles. Nanoplates with diameters of 10–350 nm and diameter-to-thickness ratios of 3–30 were synthesized hydrothermally and stabilized in 1-butanol with dodecylbenzene sulphonic acid. The nanoplates were then deposited from the suspension on gold-coated substrates and dried with or without an applied magnetic field. In both cases the nanoplates aligned preferentially in the plane of the substrate, as evidenced by the scanning electron microscopy observations. To compare the influence of the magnetic field and the magnetic dipole–dipole interactions with that of the nanoparticle shape anisotropy, the alignment of paramagnetic erbium oxide (Er2O3) nanoplates was also studied. A lower degree of alignment was obtained with the erbium oxide than with the barium ferrite nanoplates. Barium ferrite films with a minimum orientation of 90% were prepared from the deposits after sintering at 1150 °C for 5 h. A comparable alignment of the erbium oxide films was induced hydrodynamically during the electrophoretic deposition.