Three dimensional instability of the flexible ferromagnetic filament loop

K. Ērglis¹ - R. Livanoviċs¹ - A. Cēbers²

¹ University of Latvia, 8 Zellu, Riga, LV-1002, Latvia
² Institute of Physics, University of Latvia, Salaspils, LV-2169, Latvia

Abstract
Dynamics of flexible ferromagnetic filaments in an external magnetic field is considered. We report the existence of a buckling instability of the ferromagnetic filament at magnetic field reversion, which leads to the formation of a metastable loop. Its relaxation through three dimensional transformation of the configurations is observed experimentally and confirmed by numerical simulations. The bending modulus of the flexible ferromagnetic filaments synthesized by linking micron-sized core-shell ferromagnetic particles with DNA fragments is estimated by comparing the parameters of the loops observed in experiment with theoretical calculations. Formation of the loop and its relaxation are characterized by the numerically calculated writhe number. The relaxation time of the loop allows us to estimate the hydrodynamic drag of the filament. Figs 10, Refs 22.