Dynamic susceptibility investigation of biocompatible magnetic fluids: The surface coating effect

In this study room-temperature dynamic susceptibility measurements were used to investigate magnetite nanoparticles surface-coated with dextran and dimercaptosuccinic acid, both dispersed as biocompatible magnetic fluids. Multicomponent susceptibility curves were associated with the presence of monomers and dimers in the sample. Transmission electron microscopy data have been used to support the analysis carried out with the susceptibility data. The field dependence of the peak position of the imaginary component of the dynamical susceptibility was analyzed within the picture of an asymmetric double-well potential for the relaxation of the magnetic moment associated with the magnetite nanoparticle. The nanoparticle size dependence of the susceptibility peak position was taken into account in the data analysis. Nanoparticle-size parameters obtained from the analysis of the susceptibility data of the two samples (3.7 and 6.1 nm) are in very good agreement with the values obtained from the fitting of the electron microscopy data (3.1 and 5.6 nm). (c) 2005 American Institute of Physics.