Search for Vortex-Type Spin Structures in Iron Nanoparticles

Magnetic nanoparticles (MNPs) exhibit physical, chemical, electrical, and biological
properties that can significantly differ from the bulk material and are therefore used for
catalysis, high density magnetic data storage, drug delivery systems, ferrofluids, and medical
applications. Often in application-oriented studies, the magnetization distribution of MNPs is
assumed to be spatially uniform (macrospin model), and the possible intraparticle spin
misalignment is commonly not taken into account. Here, based on micromagnetic SANS
simulations, we propose to experimentally study the transition from a single-domain to a
vortex-type texture in spherical Fe MNPs and the ensuing signatures in the magnetic SANS
cross section and correlation function. This work will contribute to the fundamental
understanding of the magnetic SANS technique.