Optical transmission versus ac magnetization measurements for monitoring colloidal Ni nanorod rotational dynamics

Gratz, Micha; Tschöpe, Andreas

doi:10.1088/1361-6463/50/1/015001

Cited by 13 publications

(10 citation statements)

References 54 publications

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“…They described the field dependence using a parameter for the change of the peak position of χ 1 and assumed that the inflection point of χ 1 would follow the same dependence. Later, Gratz and Tschöpe followed the same approach but used the peak position found from fits of a Debye model to the spectra 16 . None of the above approximations account for the change of the curve shape.…”

Section: Low-field Behaviourmentioning

confidence: 99%

“…A slightly improved expression introduced by Ludwig et al 2 was shown to fit the peak position of the imaginary part of the magnetic susceptibility for large applied magnetic field amplitudes 15 . Later Gratz and Tschöpe also proposed an improved ACS approximation by fitting the Debye model to spectra obtained from Fokker-Planck calculations 16 . For all approximations, the curve shape was assumed identical to that of the Debye model.…”

Section: Introductionmentioning

confidence: 99%

“…The modulation of the optical transmission through a colloidal MNP dispersion in response to an applied oscillating magnetic field has also been used to study the nanoparticle dynamics [16][17][18][19][20] . The method was termed optomagnetic (OM) to distinguish it from the traditional magnetooptical effects such as the Kerr and Faraday effects.…”

Section: Introductionmentioning

confidence: 99%

“…We recently developed an analytical model for the low-field OM signal from particles with a permanent magnetic moment using fundamental relations and a few assumptions 20 . The dynamic OM signal at finite fields has also been calculated using the Fokker-Planck equation 16 ; however, in that study only the characteristic frequency, defined as the frequency with a phase delay of 45 • relative to the square of the magnetic field signal, was considered.…”

Section: Introductionmentioning

confidence: 99%

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Field-dependent dynamic responses from dilute magnetic nanoparticle dispersions

et al. 2018

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The response of magnetic nanoparticles (MNPs) to an oscillating magnetic field outside the linear response region is important for several applications including magnetic hyperthermia, magnetic resonance imaging and biodetection. The size and magnetic moment are two critical parameters for the performance of a colloidal MNP dispersion. We present and demonstrate the use of optomagnetic (OM) and AC susceptibility (ACS) measurements vs. frequency and magnetic field strength to obtain the size and magnetic moment distributions including the correlation between the distributions. The correlation between the size and the magnetic moment contains information on the morphology and intrinsic structure of the particle. In OM measurements, the variation of the second harmonic light transmission through a dispersion of MNPs is measured in response to an oscillating magnetic field. We solve the Fokker-Planck equations for MNPs with a permanent magnetic moment, and develop analytical approximations to the ACS and the OM signals that also account for the change in the curve shapes with increasing field strength. Further, we describe the influence of induced magnetic moments on the signals, by solving the Fokker-Planck equation for particles, which apart from the permanent magnetic moment may also have an induced magnetic moment and shape anisotropy. Using the results from the Fokker-Planck calculations we fit ACS and OM measurements on two multi-core particle systems. The obtained fit parameters also describe the correlations between the magnetic moment and size of the particles. From such an analysis on a commercially available polydisperse multicore particle system with an average particle size of 80 nm, we find that the MNP magnetic moment is proportional to the square root of the hydrodynamic size.

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Section: Low-field Behaviourmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Field-dependent dynamic responses from dilute magnetic nanoparticle dispersions

et al. 2018

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“…Optical measurements on magnetically actuated nanoparticles have been used extensively for biodetection assays [9][10][11][12][13][14][15][16] as well as for the characterization of the hydrodynamic size of magnetic nanorods. 10,17,18 We have previously introduced a simple optical method that measures the modulation of light transmitted through an MNP suspension in response to an applied axial oscillating magnetic field, and demonstrated this method for biodetection. [12][13][14][15][16] The basis for the method is measurements of the magnetic-fieldinduced modulation of the optical extinction of the MNP suspension.…”

Section: Introductionmentioning

confidence: 99%