Effects of surfactant friction on Brownian magnetic relaxation in nanoparticle ferrofluids
نویسندگان
چکیده
Measurement of the variation of relaxation frequency of Brownian rotation of magnetic nanoparticles in a ferrofluid due to binding of organic molecules is a possible tool for detection of biomolecules in solution. We investigate frequencyand temperature-dependent magnetic behavior of model ferro-fluids of surfactant-coated Co nanoparticles, 20 nm in diameter, in dichlorobenzene in a wide concentration range. At room temperature the most diluted ferrofluids have a single relaxation frequency determined by the fluid viscosity and effective particle volume. Increasing concentration leads to an appearance of the second, low-frequency relaxation peak, attributed to the effective viscosity associated with interparticle friction. © 2005 American Institute of Physics. fDOI: 10.1063/1.1855195g
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