Bender, P;
Wetterskog, E;
Honecker, D;
Fock, J;
Frandsen, C;
Moerland, C;
Bogart, LK;
... Johansson, C; + view all
(2018)
Dipolar-coupled moment correlations in clusters of magnetic nanoparticles.
Physical Review B
, 98
(22)
, Article 224420. 10.1103/PhysRevB.98.224420.
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Abstract
Here, we resolve the nature of the moment coupling between 10-nm dimercaptosuccinic acid–coated magnetic nanoparticles. The individual iron oxide cores were composed of > 95 % maghemite and agglomerated to clusters. At room temperature the ensemble behaved as a superparamagnet according to Mössbauer and magnetization measurements, however, with clear signs of dipolar interactions. Analysis of temperature-dependent ac susceptibility data in the superparamagnetic regime indicates a tendency for dipolar-coupled anticorrelations of the core moments within the clusters. To resolve the directional correlations between the particle moments we performed polarized small-angle neutron scattering and determined the magnetic spin-flip cross section of the powder in low magnetic field at 300 K. We extract the underlying magnetic correlation function of the magnetization vector field by an indirect Fourier transform of the cross section. The correlation function suggests nonstochastic preferential alignment between neighboring moments despite thermal fluctuations, with anticorrelations clearly dominating for next-nearest moments. These tendencies are confirmed by Monte Carlo simulations of such core clusters.
| Type: | Article |
|---|---|
| Title: | Dipolar-coupled moment correlations in clusters of magnetic nanoparticles |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1103/PhysRevB.98.224420 |
| Publisher version: | https://doi.org/10.1103/PhysRevB.98.224420 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Dipolar interaction, Superparamagnetism, Nanoclusters, Nanoparticles, Magnetization measurements, Monte Carlo methods, Mössbauer spectroscopy, Neutron diffraction, Small angle neutron scattering |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10105864 |
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