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

Buttner, Markus and Weber, Peter and Schmidl, Frank and Seidel, Paul and Roder, Michael and Schnabelrauch, Matthias and Wagner, Kerstin and Gornert, Peter and Glockl, Gunnar and Weitschies, Werner (2011) Investigation of magnetic active core sizes and hydrodynamic diameters of a magnetically fractionated ferrofluid. Journal of Nanoparticle Research, 13 (1). pp. 165-173.

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Official URL: http://www.springerlink.com/content/a3h90733661t6k...

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.

Item Type:Article
Subjects:Physical Science > Nanophysics
Physical Science > Nano objects
Material Science > Nanochemistry
Material Science > Nanostructured materials
Divisions:Faculty of Engineering, Science and Mathematics > School of Physics
Faculty of Engineering, Science and Mathematics > School of Chemistry
ID Code:10571
Deposited By:JNCASR
Deposited On:28 Feb 2011 06:34
Last Modified:28 Feb 2011 06:34

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