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Magnetic ac Susceptibility Study of Relaxation Mechanisms in Aqueous Magnetite Nanoparticles
New Phys.: Sae Mulli 2019; 69: 1226~1230
Published online December 31, 2019;
© 2019 New Physics: Sae Mulli.

Sunghyun YOON*

Department of Physics, Gunsan National University, Gunsan 54150, Korea
Correspondence to:
Received September 26, 2019; Revised October 17, 2019; Accepted October 17, 2019.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The temperature and the frequency dependences of the ac susceptibility are measured for 13-nm and 16-nm magnetite nanoparticles in aqueous dispersions. Two kinds of thermal activation-type relaxation peaks were observed in the imaginary part of the susceptibility for 13 nm magnetite nanoparticles whereas only a single relaxation peak existed for the 16-nm sample. The physical origins for those relaxation mechanisms were identified using quantitative analyses based on the Neel-Arrhenius and the Vogel-Fulcher models. As a result, a single-particle relaxation from isolated nanoparticles and a relaxation from clusters of agglomerated nanoparticles were found to coexist in a sample. The particles in the clusters experienced an additional energy barrier represented by a simple shift T$_0$ in the imaginary part of the ac susceptibility due to the interparticle dipolar interaction. Furthermore, dominant relaxation took place at temperature near room temperature for the 16-nm magnetite sample, which makes it a more efficient candidate for magnetic hyperthermia applications.
PACS numbers: 75.30.-m
Keywords: Magnetic ac susceptibility, Interparticle interaction, Magnetic nanoparticles, Relaxation

January 2020, 70 (1)
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