On the interpretation of Mössbauer spectra of magnetic nanoparticles

Fock, Jeppe; Hansen, Mikkel Fougt; Frandsen, Cathrine; Mørup, Steen

doi:10.1016/j.jmmm.2017.08.070

Cited by 47 publications

(22 citation statements)

References 52 publications

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“…But it can be noted that the broad asymmetric lines in the Mössbauer spectra observed at 200 K ( Fig. 3(a) and (b)) are typical for magnetic fluctuations governed by an interaction field arising from interparticle interactions [81]. Additionally we can conclude from the observed splitting of the spectra at 200 K that the cores are still thermally blocked, although it is worth mentioning that at 295(5) K they are clearly superparamagnetic on the Mössbauer time scale of ≈ 1 ns ( Fig.…”

Section: A Structural and Magnetic Pre-characterizationmentioning

confidence: 95%

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

et al. 2018

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Here, we resolve the nature of the moment coupling between 10-nm DMSA-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 non-stochastic 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.

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Section: A Structural and Magnetic Pre-characterizationmentioning

confidence: 95%

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

et al. 2018

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“…The pre-factor τ 0 is generally taken as 10 −9 − 10 −10 s, although it is sensitive on several parameters such as the particle size, temperature and dipolar interactions. 17,18 In Eq. (2), η is the viscosity of the surrounding medium and D h is the hydrodynamic diameter of the particle, including surrounding surfactant and/or depletion layer.…”

Section: Introductionmentioning

confidence: 99%

Relating Magnetic Properties and High Hyperthermia Performance of Iron Oxide Nanoflowers

Bender

Fock²,

Frandsen³

et al. 2018

J. Phys. Chem. C

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125

101

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“…Several recent studies have been focused on understanding the influence of the particle sizes on the magnetic properties of hematite. These studies have shown that the particle size of α − Fe 2 O 3 nanoparticles has a significant impact on the magnetic properties, in particular on the Morin transition, the Néel temperature and superparamagnetic relaxation of the nanoparticles [43,46]. Consequently, synthesis methods and systems where the size of magnetic nanoparticles can be changed in a controllable manner are the most useful for studying the above-described effects.…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties of hematite (α − Fe₂O₃) nanoparticles synthesized by sol-gel synthesis method: The influence of particle size and particle size distribution

Tadić

Panjan

Tadić

et al. 2019

Journal of Electrical Engineering

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Using the sol-gel method we synthesized hematite (α − Fe2O3) nanoparticles in a silica matrix with 60 wt % of hematite. X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra of the sample demonstrate the formation of the α − Fe2O3 phase and amorphous silica. A transmission electron microscopy (TEM) measurements show that the sample consists of two particle size distributions of the hematite nanoparticles with average sizes around 10 nm and 20 nm, respectively. Magnetic properties of hematite nanoparticles were measured using a superconducting quantum interference device (SQUID). Investigation of the magnetic properties of hematite nanoparticles showed a divergence between field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves and two maxima. The ZFC magnetization curves displayed a maximum at around TB = 50 K (blocking temperature) and at TM = 83 K (the Morin transition). The hysteresis loop measured at 5 K was symmetric around the origin, with the values of coercivity, remanent and mass saturation magnetization HC10K ≈ 646 A/cm, (810 Oe), Mr10K = 1.34 emu/g and MS10K = 6.1 emu/g respectively. The absence of both coercivity (HC300K = 0) and remanent magnetization (Mr300K = 0) in M(H) curve at 300 K reveals super-paramagnetic behavior, which is desirable for application in biomedicine. The bimodal particle size distributions were used to describe observed magnetic properties of hematite nanoparticles. The size distribution directly influences the magnetic properties of the sample.

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On the interpretation of Mössbauer spectra of magnetic nanoparticles

Cited by 47 publications

References 52 publications

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

Relating Magnetic Properties and High Hyperthermia Performance of Iron Oxide Nanoflowers

Magnetic properties of hematite (α − Fe₂O₃) nanoparticles synthesized by sol-gel synthesis method: The influence of particle size and particle size distribution

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On the interpretation of Mössbauer spectra of magnetic nanoparticles

Cited by 47 publications

References 52 publications

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

Dipolar-coupled moment correlations in clusters of magnetic nanoparticles

Relating Magnetic Properties and High Hyperthermia Performance of Iron Oxide Nanoflowers

Magnetic properties of hematite (α − Fe2O3) nanoparticles synthesized by sol-gel synthesis method: The influence of particle size and particle size distribution

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Magnetic properties of hematite (α − Fe₂O₃) nanoparticles synthesized by sol-gel synthesis method: The influence of particle size and particle size distribution