Field-induced columnar transition of biocompatible magnetic colloids: an aging study by magnetotransmissivity
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2010
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The field dependence of the optical transmission of tartrate-coated and polyaspartate-coated magnetite-based
aqueous colloids was studied. The colloidal stock samples were diluted to prepare a series of samples containing
different particle volume fractions ranging from 0.17% up to 1.52% and measured at distinct times after
preparation 1, 30, 120, 240, and 1460 days . We show that the magneto-transmissivity behavior is mainly
described by the rotation of linear chains, at the low-field range, whereas the analysis of the data provided the
measurement of the average chain length. Results also reveal that the optical transmissivity has a minimum at
a particular critical field, whose origin is related to the onset of columns of chains built from isolated particle
chains, i.e., due to a columnar phase transition. We found the critical field reducing as the particle volume
fraction increases and as the sample’s aging time increases. To investigate the origin of this phenomenon we
used phase condensation models and Mie’s theory applied to a chain of spheres and to an infinite cylinder.
Possible implications for magnetophotonic colloidal-based devices and biomedical applications were
discussed.
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ELOI, M. T. A.; SANTOS JR., J. L.; MORAIS, P. C.; BAKUZIS, A. F. Field-induced columnar transition of biocompatible magnetic colloids: an aging study by magnetotransmissivity. Physical Review. E, Melville, v. 82, n. 2, e021407, 2010.