Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia

R. Hergt; R. Hiergeist; I. Hilger; W. A. Kaiser; Y. Lapatnikov; S. Margel; U. Richter

doi:10.1016/j.jmmm.2003.09.001

Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia

R. Hergt, R. Hiergeist, I. Hilger, W. A. Kaiser, Y. Lapatnikov, S. Margel, U. Richter

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

421 Scopus citations

Abstract

Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3nm and distribution width 4.9nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20Hz to 1MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410kHz for field amplitudes up to 11.7kA/m. Extremely high values of SLP in the order of 600W/g result for 400kHz and 11kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of Néel and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications.

Original language	English
Pages (from-to)	345-357
Number of pages	13
Journal	Journal of Magnetism and Magnetic Materials
Volume	270
Issue number	3
DOIs	https://doi.org/10.1016/j.jmmm.2003.09.001
State	Published - Apr 2004

Bibliographical note

Funding Information:
The present work was funded by the Deutsche Forschungsgemeinschaft under contract number HE 2878/9-2 and HI 698/3-2.

Funding

The present work was funded by the Deutsche Forschungsgemeinschaft under contract number HE 2878/9-2 and HI 698/3-2.

Funders	Funder number
Deutsche Forschungsgemeinschaft	HE 2878/9-2, HI 698/3-2

Keywords

AC Losses
Brown relaxation
Ferrofluids
Magnetic hyperthermia
Magnetic nanoparticle
Néel relaxation

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10.1016/j.jmmm.2003.09.001

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title = "Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia",

abstract = "Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3nm and distribution width 4.9nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20Hz to 1MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410kHz for field amplitudes up to 11.7kA/m. Extremely high values of SLP in the order of 600W/g result for 400kHz and 11kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of N{\'e}el and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications.",

keywords = "AC Losses, Brown relaxation, Ferrofluids, Magnetic hyperthermia, Magnetic nanoparticle, N{\'e}el relaxation",

author = "R. Hergt and R. Hiergeist and I. Hilger and Kaiser, \{W. A.\} and Y. Lapatnikov and S. Margel and U. Richter",

note = "Funding Information: The present work was funded by the Deutsche Forschungsgemeinschaft under contract number HE 2878/9-2 and HI 698/3-2. ",

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T1 - Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia

AU - Hergt, R.

AU - Hiergeist, R.

AU - Hilger, I.

AU - Kaiser, W. A.

AU - Lapatnikov, Y.

AU - Margel, S.

AU - Richter, U.

N1 - Funding Information: The present work was funded by the Deutsche Forschungsgemeinschaft under contract number HE 2878/9-2 and HI 698/3-2.

PY - 2004/4

Y1 - 2004/4

N2 - Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3nm and distribution width 4.9nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20Hz to 1MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410kHz for field amplitudes up to 11.7kA/m. Extremely high values of SLP in the order of 600W/g result for 400kHz and 11kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of Néel and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications.

AB - Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3nm and distribution width 4.9nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20Hz to 1MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410kHz for field amplitudes up to 11.7kA/m. Extremely high values of SLP in the order of 600W/g result for 400kHz and 11kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of Néel and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications.

KW - AC Losses

KW - Brown relaxation

KW - Ferrofluids

KW - Magnetic hyperthermia

KW - Magnetic nanoparticle

KW - Néel relaxation

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Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia

Abstract

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Keywords

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