Dresden 2026 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 25: Franco-German Session on Granular Matter II

DY 25.2: Vortrag

Dienstag, 10. März 2026, 14:15–14:30, HÜL/S186

Magnetic-Field Controlled Self-Diffusion and Clustering in Ferrogranular Mixtures — •Oksana Bilous¹, Kirill Okrugin¹, Ali Lakkis², Richter Reinhard², and Sofia Kantorovich¹ — ¹Computational and Soft Matter Physics, University of Vienna, Vienna, Austria — ²Experimental Physics 5, University of Bayreuth, Bayreuth, Germany

We investigate self-diffusion in ferrogranular mixtures of magnetic and glass beads via Langevin/molecular dynamics of quasi-2D Stockmayer spheres mixed with repulsive non-magnetic ones, complemented by mm-scale experiments. We vary out-of-plane magnetic induction and total area fraction. The field aligns dipoles and reduces in-plane aggregation by inducing repulsion, while dipole-dipole interactions and central attractions (or susceptibility in experiments) drive chain-like and compact clustering. Increasing area fraction counteracts field-induced suppression and stabilizes larger clusters. Single magnetic particles and glass beads remain mostly diffusive, with diffusion only weakly concentration dependent, whereas particles embedded in clusters show persistent subdiffusion. The field also alters diffusion type: cluster-bound particles exhibit robustly non-Gaussian dynamics that amplify with area fraction and field. At sufficiently high induction and crowding, the glass component becomes non-Gaussian, revealing field-driven dynamical freezing of the non-magnetic species. Simulations and experiments consistently show how external fields, dipolar self-assembly, and crowding govern transport in ferrogranular layers.

Keywords: Molecular dynamic simulation; Ferrogranular system; Stockmayer system