Alignment of iron nanoparticles in a magnetic field due to shape anisotropy

• Monte Carlo simulation of net magnetic moment at super-Curie temperatures.
• Simulation based scaling law for dipole–dipole interaction energy.
• Scaled dipole–dipole interaction energy used to simulate magnetic texturing.
• Simulations used to explain magnetic texturing in a Fe–Ni–Co–Al–B alloy.

During high magnetic field solidification processing there is evidence for the alignment of nanoscale metallic particles with elongated morphologies that nucleate from a liquid metal. Such alignment occurs well above the Curie temperature of the particle where the magneto-crystalline anisotropy energy and exchange energy contributions are negligible. The main driving force for alignment is the magnetic shape anisotropy. Current understanding of the phenomenon is not adequate to quantify the effect of particle size, aspect ratio, temperature and the magnetic field on particle alignment. We demonstrate a Monte Carlo approach coupled with a scaling law for the dipole–dipole interaction energy as a function of the particle size to identify the conditions under which such alignment is possible.