On the Theory of Debye and Néel Relaxation of Single Domain Ferromagnetic Particles

Coffey, W. T.; Cregg, P.J.; Kalmykov, Yuri

doi:10.1002/9780470141410.ch5

Cited by 96 publications

(102 citation statements)

References 43 publications

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“…To investigate how effective this interaction plays its role, we paid attention to the spectral relaxation responses of the suspended particles at different C p values. In principle, the relaxation responses including the frequency-dependent χAA can be generalized into moment rotation (Néel relaxation) 22) and particle rotation (Brownian relaxation). 18) However, as we used an extremely low oscillatory field, the mechanism should statistically be the Brownian relaxation.…”

Section: Ion Concentration-dependent Electrostatic Interparticle Intementioning

confidence: 99%

Dipolar magnetism and electrostatic repulsion of colloidal interacting nanoparticle system

Trisnanto

Yasuda

Kitamoto

2018

Jpn. J. Appl. Phys.

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Thermally activated Brownian kinetics of magnetic nanoparticles in water potentially results in particle aggregation, owing to magnetic and electrostatic interparticle interactions. To determine the significance of those competing interactions in changing the equilibrium hydrodynamic particle volume, we examined the mean distance between polydispersed particles as an important factor for initiating a secondary particle clustering among individually dispersed particles or their primary cluster structures. We particularly characterized the magnetic properties of a superparamagnetic ferrofluid in different ionic environments and at different particle (mass) concentrations. Regarding the concentration of ionic components added to dense ferrofluid samples, the spectral relaxation shift and the reduction in magnetic susceptibility were attributed to different hydrodynamic polydispersities of aggregates. However, no substantial changes in complex susceptibility with increasing ion concentration in dilute ferrofluid samples were confirmed, which indicates relatively stable dipolar-interactions. Regarding the adjustment of particle concentration, we found that the changes in the effective relaxation time constant are proportionally associated with the magnetopotential energy of a given oscillatory magnetic field.

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Section: Ion Concentration-dependent Electrostatic Interparticle Intementioning

confidence: 99%

Dipolar magnetism and electrostatic repulsion of colloidal interacting nanoparticle system

Trisnanto

Yasuda

Kitamoto

2018

Jpn. J. Appl. Phys.

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“…The starting point for calculation of the relaxation time is the Fokker-Planck equation [26]. This equation was solved by Brown [27] in case of high and low energy barrier.…”

Section: Stochastic Approach For the Magnetic Relaxation Dynamics In mentioning

confidence: 99%

The Néel Magnetic Relaxation Dynamics in Nanoparticle Systems - Phenomenological Approach versus Stochastic Approach

Osaci

2016

Acta Phys. Pol. A

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In nanomagnetism, the studies of magnetic nanoparticle systems are of particular interest from both experimental and theoretical points of view. Experimentally, the measurements made on such a system are hard to interpret. It is very difficult to distinguish the effect of the magnetic dipole interactions from the effects of size distribution or effective magnetic anisotropy constants. In this respect, the simulation models can help. This paper presents a study comparing the two conventional approaches, using simulation models for the magnetic relaxation dynamics of nanoparticle systems, i.e. a phenomenological Ising-type approach, on two levels, and a stochastic approach. The paper also shows a way of using these approaches in creating a model to simulate the Néel magnetic relaxation time for aligned magnetic nanoparticle systems.

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“…When a magnetic field is applied to ferrofluid, magnetizations in magnetic nanoparticles orient along the direction of the magnetic field by two relaxation mechanisms, Brownian relaxation [9] and Neel relaxation [10]. Brownian relaxation is particle rotation characterized by a relaxation time kT V H B 3 ( 1 ) where H V is the hydrodynamic volume of the particle, is the dynamic viscosity of the carrier fluid, k is the Boltzmanns constant and T is the absolute temperature.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Fe3O4 nanorods designed for liquid-phase magnetic biosensing

Yasuda

Kitamoto

2018

AIP Conference Proceedings

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Abstract. Alternating current (ac) susceptibility-based magnetic biosensing techniques in liquids are promising biomedical applications of magnetic nanoparticles because the methods have a potential for realizing the simple washfree detection of diseases. Controlling magnetic relaxation of nanoparticles is crucial in the biosensing; Brownian relaxation based on the particle rotation in liquids should be dominant to improve the sensitivity. Therefore, we focus on magnetically anisotropic Fe3O4 nanorods because it is considered that the particle rotation dominates magnetic response of suspended Fe3O4 nanorods due to the shape magnetic anisotropy. In the present paper, the Fe3O4 nanorods are fabricated and the dynamic magnetic response of Fe3O4 nanorods is evaluated under the liquid phase and the solid phase.

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On the Theory of Debye and Néel Relaxation of Single Domain Ferromagnetic Particles

Cited by 96 publications

References 43 publications

Dipolar magnetism and electrostatic repulsion of colloidal interacting nanoparticle system

Dipolar magnetism and electrostatic repulsion of colloidal interacting nanoparticle system

The Néel Magnetic Relaxation Dynamics in Nanoparticle Systems - Phenomenological Approach versus Stochastic Approach

Fabrication of Fe3O4 nanorods designed for liquid-phase magnetic biosensing

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