Magnetic Vortex States in Toroidal Iron Oxide Nanoparticles: Combining Micromagnetics with Tomography

• DOI: 10.1021/acs.nanolett.0c02795
• Publication Date: 2020-09-11T18:19:42Z
• Authors: George R. Lewis; James C. Loudon; Robert Tovey; Yen-Hua Chen; Andrew P. Roberts; Richard J. Harrison; Paul A. Midgley; Emilie Ringe
• Keywords: Micromagnetics; Vortex state; Metastability

Iron oxide nanorings have great promise for biomedical applications because of their magnetic vortex state, which endows them with a low remanent magnetization while retaining large saturation magnetization. Here we use micromagnetic simulations to predict the exact shapes that can sustain vortices, using toroidal model geometry variable diameter, ring thickness, and eccentricity. Our phase diagram is then compared experimental geometries obtained by electron tomography. High axial eccentricity thickness are found be key factors forming states avoiding net-magnetized metastable states. We also find defects from perfect increase stray field associated they make state more energetically accessible. These results constitute an important step toward optimizing behavior iron nanoparticles.