Journal of Nanoparticle Research

, Volume 13, Issue 1, pp 165–173

Investigation of magnetic active core sizes and hydrodynamic diameters of a magnetically fractionated ferrofluid

Authors

  • Markus Büttner
    • Institute of Solid State PhysicsFriedrich Schiller Universität Jena
  • Peter Weber
    • Institute of Solid State PhysicsFriedrich Schiller Universität Jena
  • Frank Schmidl
    • Institute of Solid State PhysicsFriedrich Schiller Universität Jena
    • Institute of Solid State PhysicsFriedrich Schiller Universität Jena
  • Michael Röder
    • INNOVENT e.V.
  • Matthias Schnabelrauch
    • INNOVENT e.V.
  • Kerstin Wagner
    • INNOVENT e.V.
  • Peter Görnert
    • INNOVENT e.V.
  • Gunnar Glöckl
    • Institute of Pharmacy, Biopharmaceutics & Pharmaceutical TechnologyErnst-Moritz-Arndt University of Greifswald
  • Werner Weitschies
    • Institute of Pharmacy, Biopharmaceutics & Pharmaceutical TechnologyErnst-Moritz-Arndt University of Greifswald
Research Paper

DOI: 10.1007/s11051-010-0015-2

Cite this article as:
Büttner, M., Weber, P., Schmidl, F. et al. J Nanopart Res (2011) 13: 165. doi:10.1007/s11051-010-0015-2

Abstract

In this work we address the question which relates between the size of the magnetically active core of magnetic nanoparticles (MNPs) and the size of the overall particle in the solution (the so-called hydrodynamic diameter dhyd) exists. For this purpose we use two methods of examination that can deliver conclusions about the properties of MNP which are not accessible with normal microscopy. On the one hand, we use temperature dependent magnetorelaxation (TMRX) method, which enables direct access to the energy barrier distribution and by using additional hysteresis loop measurements can provide details about the size of the magnetically active cores. On the other hand, to determine the size of the overall particle in the solution, we use the magnetooptical relaxation of ferrofluids (MORFF) method, where the stimulation is done magnetically while the reading of the relaxation signal, however, is done optically. As a basis for the examinations in this work we use a ferrofluid that was developed for medicinal purposes and which has been fractioned magnetically to obtain differently sized fractions of MNPs. The two values obtained through these methods for each fraction shows the success in fractioning the original solution. Therefore, one can conclude a direct correlation between the size of the magnetically active core and the size of the complete particle in the solution from the experimental results. To calculate the size of the magnetically active core we found a temperature dependent anisotropy constant which was taken into account for the calculations. Furthermore, we found relaxation signals at 18 K for all fractions in these TMRX measurements, which have their origin in other magnetic effects than the Néel relaxation.

Keywords

Magnetic nanoparticlesTemperature dependent magnetorelaxationMagnetooptical relaxationAnisotropyHydrodynamic sizeMagnetiteMaghemiteCore sizeColloids

Copyright information

© Springer Science+Business Media B.V. 2010