Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 18: Physics of polymers II
CPP 18.3: Vortrag
Dienstag, 8. März 2005, 11:45–12:00, TU C130
Bending of magnetic filaments under a magnetic field — •Michael Winklhofer1 and Valera Shcherbakov2 — 1Dept. für Geo- und Umweltwissenschaften, LMU Muenchen, Theresienstr. 41/ IV, 80333 Muenchen — 2Institute for the Physics of the Earth, Russian Academy of Science, Borok, Yaroslaskaja oblast, Russia
Filaments consisting of magnetic particles chained by molecular linkers have been used to to probe elastic parameters on molecular scale. Other applications may comprise magnetically controlled valves or shape memory materials. We have derived analytical expressions for the equilibrium shape of magnetic fibres, considering two end-member cases, a) magnetic particles concentrated at the free end of cantilevered rods or tubes, and b) (superpara)magnetic particles distributed over the whole length of the filament. Our analysis yields also metastable equilibrium states (MES), which only exist above a critical filament length, but become more stable with increasing magnetic field. The MES for case a) are, like the ground state, circular arcs, but more strongly bent. The multiform MES in case b), which comprise hairpin, sinuous, or even closed shapes, have recently been observed in experiments, too. Because of their simple experimental realization, case a) magnetic filaments are deemed highly suitable for micro-mechanical experiments on long chains of polymer molecules.