Alignment of magnetic uniaxial particles in a magnetic field: Simulation

• We simulate the magnetic alignment of ensemble of Nd–Fe–B spherical uniaxial particles.
• Anisotropic particles as a combination of spherical particles are constructed.
• Influence of the particle shape anisotropy and friction on the alignment is analyzed.
• We compare calculated and experimental data on field dependence of magnetic alignment.
• The results render the experimental dependence.

The numerical investigations of the process of alignment of magnetically uniaxial Nd–Fe–B powders in an applied magnetic field were carried out using the discrete element method (DEM). It is shown that magnetic alignment of ensemble of spherical particles provides extremely high degree of alignment, which is achieved in low magnetic fields. A model of formation of anisotropic particles as a combination of spherical particles is suggested. The influence of the shape anisotropy and friction coefficient on the alignment degree was analyzed. The increase in the friction coefficient leads to a decrease in the alignment degree; the simulation results are in qualitative agreement with experimental dependences. It is shown that in magnetic fields higher than 5 T, the calculated field dependences of the alignment degree quantitatively render the experimental data. The increase of about 6% in the alignment degree in the experiments with addition of internal lubricant can be explained by the decrease of 14% in friction coefficient.