Dynamic simulations of the dipolar driven demagnetization process of magnetic multi-core nanoparticles

Weddemann, Alexander; Auge, Alexander; Kappe, Daniel; Wittbracht, Frank; Hütten, Andreas

doi:10.1016/j.jmmm.2009.10.031

Cited by 22 publications

(28 citation statements)

References 18 publications

(22 reference statements)

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“…Therefore, the microscopic dynamics are not in the scope of this work and the value of the damping parameter may be adjusted to provide a high numerical convergence rate. We chose α = 1 [26]. For the integration with respect to time, a backward differential formula of fifth order is applied.…”

Section: Methodsmentioning

confidence: 99%

Hydrogen-plasma-induced magnetocrystalline anisotropy ordering in self-assembled magnetic nanoparticle monolayers

Weddemann¹,

Meyer²,

Regtmeier³

et al. 2013

Beilstein J. Nanotechnol.

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SummarySelf-assembled two-dimensional arrays of either 14 nm hcp-Co or 6 nm ε-Co particle components were treated by hydrogen plasma for various exposure times. A change of hysteretic sample behavior depending on the treatment duration is reported, which can be divided in two time scales: oxygen reduction increases the particle magnetization during the first 20 min, which is followed by an alteration of the magnetic response shape. The latter depends on the respective particle species. Based on the Landau–Lifshitz equations for a discrete set of magnetic moments, we propose a model that relates the change of the hysteresis loops to a dipole-driven ordering of the magnetocrystalline easy axes within the particle plane due to the high spatial aspect ratio of the system.

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Section: Methodsmentioning

confidence: 99%

Hydrogen-plasma-induced magnetocrystalline anisotropy ordering in self-assembled magnetic nanoparticle monolayers

Weddemann¹,

Meyer²,

Regtmeier³

et al. 2013

Beilstein J. Nanotechnol.

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“…It is seen that MMFT1 [Eqs. (25) and (26)] and MMFT2 [Eqs. (25) and (27)] give good agreement with the simulation data in the weak field range (ξ < 1).…”

Section: A Magnetically Isotropic Particles In a Bulk Solid Matrixmentioning

confidence: 99%

“…This gives hope that approximations Eq. (39) derived for a bulk system will work for small clusters as (26) and (28)] for the same volume fractions, dot-dashed curves are predictions of MMFT2 [Eqs. (27) and (28)].…”

Section: A Magnetically Isotropic Particles In a Bulk Solid Matrixmentioning

confidence: 99%

“…For simplicity, it is sometimes assumed that microspheres and nanoclusters contain non-interacting and magnetically isotropic single-domain particles 7,[20][21][22] . However, in recent years quasi-spherical rigid clusters of different sizes have been actively studied via numerical simulations 11,[23][24][25][26][27][28] . And it has been repeatedly demonstrated that interactions between embedded particles as well as their magnetic anisotropy can have a noticeable impact on the cluster static 11,[23][24][25] and dynamic [25][26][27][28] magnetic properties.…”

Section: Introductionmentioning

confidence: 99%

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Equilibrium magnetization of a quasispherical cluster of single-domain particles

Кузнецов

2018

Phys. Rev. B

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Equilibrium magnetization curve of a rigid finite-size spherical cluster of single-domain particles is investigated both numerically and analytically. The spatial distribution of particles within the cluster is random. Dipole-dipole interactions between particles are taken into account. The particles are monodisperse. It is shown, using the stochastic Landau-Lifshitz-Gilbert equation, that the magnetization of such clusters is generally lower than predicted by the classical Langevin model. In a broad range of dipolar coupling parameters and particle volume fractions, the cluster magnetization in the weak field limit can be successfully described by the modified mean-field theory, which was originally proposed for the description of concentrated ferrofluids. In moderate and strong fields, the theory overestimates the cluster magnetization. However, predictions of the theory can be improved by adjusting the corresponding mean-field parameter. If magnetic anisotropy of particles is additionally taken into account and if the distribution of the particles' easy axes is random and uniform, then the cluster equilibrium response is even weaker. The decrease of the magnetization with increasing anisotropy constant is more pronounced at large applied fields. The phenomenological generalization of the modified mean-field theory, that correctly describes this effect for small coupling parameters, is proposed.

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“…1(b)). Due to their microstructure a complex dipole-dipole interaction occurs which governs the magnetic properties of such a system [13,14]. A typical magnetization behaviour in respect to an external magnetic field is shown in Fig.…”

Section: B Magnetic Beads and Nanoparticlesmentioning

confidence: 99%

Magnetoresistive Detection of Magnetic Beads and Nanoparticles: Spatial Resolution and Number Sensitve Detection

Weddemann

Auge

Albon

et al. 2010

2010 Fourth International Conference on Quantum, Nano and Micro Technologies

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The detection capability of magnetic beads and nanoparticles by tunneling magnetoresistance sensors is analyzed in a finite element framework. The limitations for single particle detection and the determination of the particle position are investigated. It will be shown how varying the geometrical sensor design may readily be employed to adjust the setup to a specific measurement task. Especially, we show up strategies increasing the sensitivity by introducing magnetically soft areas. Further, number sensitive detections are discussed and the influence of dipolar particle coupling on the measured signal is calculated.

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Dynamic simulations of the dipolar driven demagnetization process of magnetic multi-core nanoparticles

Cited by 22 publications

References 18 publications

Hydrogen-plasma-induced magnetocrystalline anisotropy ordering in self-assembled magnetic nanoparticle monolayers

Hydrogen-plasma-induced magnetocrystalline anisotropy ordering in self-assembled magnetic nanoparticle monolayers

Equilibrium magnetization of a quasispherical cluster of single-domain particles

Magnetoresistive Detection of Magnetic Beads and Nanoparticles: Spatial Resolution and Number Sensitve Detection

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