Hysteresis in Two Dimensional Arrays of Magnetic Nanoparticles

Anand, Manish

doi:10.48550/arxiv.2104.02961

Cited by 4 publications

(9 citation statements)

References 53 publications

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“…In for weakly interacting MNPs [56]. The observation of fastening of magnetic relaxation due to antiferromagnetic coupling induced by dipolar interaction is in perfect agreement with our recent work [52]. We found characteristic magnetic hysteresis of antiferromagnetic dominance in a square arrangement of MNPs [52].…”

Section: Simulations Resultssupporting

confidence: 91%

Relaxation in Ordered Assembly of Magnetic Nanoparticles

Anand

2021

Preprint

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We study the relaxation characteristics in the two-dimensional (l x × l y ) array of magnetic nanoparticles (MNPs) as a function of aspect ratio A r = l y /l x , dipolar interaction strength h d and anisotropy axis orientation using computer simulation. The anisotropy axes of all the MNPs are assumed to have the same direction, α being the orientational angle. Irrespective of α and A r , the functional form of the magnetization-decay curve is perfectly exponentially decaying with h d ≤ 0.2. There exists a transition in relaxation behaviour at h d ≈ 0.4; magnetization relaxes slowly for α ≤ 45 • ; it relaxes rapildy with α > 45 • . Interestingly, it decays rapidly for h d > 0.6, irrespective of α. It is because the dipolar interaction promotes antiferromagnetic coupling in such cases. There is a strong effect of α on the magnetic relaxation in the highly anisotropic system (A r ≥ 25). Interesting physics unfolds in the case of a huge aspect ratio A r = 400. There is a rapid decay of magnetization with α, even for weakly interacting MNPs. Remarkably, magnetization does not relax even with a moderate value of h d = 0.4 and α = 0 • because of ferromagnetic coupling dominance. Surprisingly, there is a complete magnetization reversal from saturation (+1) to −1 state with α > 60 • . The dipolar field and anisotropy axis tend to get aligned antiparallel to each other in such a case. The effective Néel relaxation time τ N depends weakly on α for small h d and A r ≤ 25.0. For large A r , there is a rapid fall in τ N as α is incremented from 0 to 90 • . These results benefit applications in data and energy storages where such controlled magnetization alignment and desired structural anisotropy are desirable.

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Section: Simulations Resultssupporting

confidence: 91%

Relaxation in Ordered Assembly of Magnetic Nanoparticles

Anand

2021

Preprint

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“…We evaluate this sum precisely without Ewald summation or a cutoff radius, similar to recent works [19,32,44]. We define a control parameter h d = D 3 /a 3 to model the variation of dipolar interaction strength.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…We apply an oscillating magnetic field to investigate the magnetic hysteresis behaviour in the ordered arrays of dipolar coupled MNPs. It is given by [32]…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…In particular, we investigate the hysteresis response as a function of aspect ratio A r = l y /l x , dipolar interaction strength h d , anisotropy orientation angle α and direction of the applied oscillating magnetic field. The kMC algorithm implement in the present article is described in detail in the references [19,32,44]. Therefore, we do not restate it to avoid duplications.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Moreover, the dipolar interaction induces the anisotropic properties by creating an additional anisotropy termed as shape anisotropy in such a system [30][31][32]. Therefore, these ordered nanoparticles ensembles provide a rich theoretical framework to study the role of dipolar interaction and magnetic anisotropy on magnetic response.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropic Effect of Dipolar Interaction in Ordered Ensembles of Nanoparticles

Anand

2021

Preprint

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We implement extensive computer simulations to investigate the hysteresis characteristics in the ordered arrays (l x × l y ) of magnetic nanoparticles as a function of aspect ratio A r = l y /l x , dipolar interaction strength h d , and external magnetic field directions. We have considered the aligned anisotropy case, α is the orientational angle. It provides an elegant en route to unearth the explicit role of anisotropy and dipolar interaction on the hysteresis response in such a versatile system. The superparamagnetic character is dominant with weak dipolar interaction (h d ≤ 0.2), resulting in the minimal hysteresis loop area. Remarkably, the double-loop hysteresis emerges even with moderate interaction strength (h d ≈ 0.4), reminiscent of antiferromagnetic coupling. These features are strongly dependent on α and A r . Interestingly, the hysteresis loop area increases with h d , provided A r is enormous, and the external magnetic field is along the y-direction. The coercive field µ o H c , remanent magnetization M r , and the heat dissipation E H also depend strongly on these parameters. Irrespective of the external field direction and weak dipolar interaction (h d ≤ 0.4), there is an increase in µ o H c with h d for a fixed α and A r ≤ 4.0. The dipolar interaction also elevates M r as long as A r is huge and the field is along the y-direction. E H is minimal for negligible and weak dipolar interaction, irrespective of A r , α, and the field directions. Notably, the magnetic interaction enhances E H if A r is enormous and the magnetic field is along the long axis of the system. These results are beneficial in various applications of interest such as digital data storage, spintronics, etc.

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Heating ability modulation by clustering of magnetic particles for precision therapy and diagnosis

Barrera¹,

Allia²,

Tiberto³

2021

J. Phys. D: Appl. Phys.

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Magnetic and thermal properties of clustered magnetite nanoparticles submitted to a high-frequency magnetic field is studied by means of rate equations. A simple model of large particle clusters (containing more than one hundred individual particles) is introduced. Dipolar interactions among clustered particles markedly modify shape and area of the hysteresis loops in a way critically dependent on particle size and cluster dimensions, thereby modulating the power released as heat to a host medium. For monodisperse and polydisperse systems, particle clustering can lead to either a significant enhancement or a definite reduction of the released power; in particular cases the same particles can produce opposite effects in dependence of the dimensions of the clusters. Modulation by clustering of the heating ability of magnetic nanoparticles has impact on applications requiring optimization and accurate control of temperature in the host medium, such as magnetic hyperthermia for precision therapy or fluid flow management, and advanced diagnostics involving magnetic tracers.

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Hysteresis in Two Dimensional Arrays of Magnetic Nanoparticles

Cited by 4 publications

References 53 publications

Relaxation in Ordered Assembly of Magnetic Nanoparticles

Relaxation in Ordered Assembly of Magnetic Nanoparticles

Anisotropic Effect of Dipolar Interaction in Ordered Ensembles of Nanoparticles

Heating ability modulation by clustering of magnetic particles for precision therapy and diagnosis

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