| In situ imaging of Field-induced hexagonal columns in magnetite ferrofluids (2006) | |||||||||||||
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| In Situ Imaging Field Induced Hexagonal Columns Magnetite Ferro uids Mark Klokkenburg Ben Erne Johannes Meeldijk Albrecht Wiedenmann Andrei Petukhov Roel Dullens and Albert Philipse Van Hoff Laboratory for Physical and Colloid Chemistry Debye Institute Utrecht University Padualaan Utrecht The Netherlands Electron Microscopy Utrecht Department Biology Utrecht University Padualaan Utrecht The Netherlands Hahn Meitner Institut Berlin Department Glienickerstrasse Berlin Germany Received August published November Field induced structures ferro uid with well ned magnetite nanoparticles with permanent magnetic dipole moment are analyzed single particle level situ cryogenic transmission electron microscopy The eld induced columnar phase locally exhibits hexagonal symmetry and con rms the structures observed simulations for ferromagnetic dipolar uids The columns are distorted lens shaped voids due the weak interchain attraction relative eld directed dipole dipole attraction Both dipolar coupling and the dipole concentration determine the dimensions and the spatial arrangement the columns Their regular spacing manifests long range end pole repulsions that eventually dominate the uctuation induced attractions between dipole chains that initiate the columnar transition DOI PhysRevLett PACS numbers Mm Nanoparticles dispersed solvent and with suf ciently large permanent magnetic dipole moment self assemble into variety magnetic equilibrium structures such closure rings and wormlike branche | |||||||||||||
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