Vortex structure in magnetic nanodots: Dipolar interaction, mobile spin model, phase transition and melting

Bailly-reyre, A.; Diep, H. T.

doi:10.1016/j.jmmm.2021.167813

Cited by 5 publications

(1 citation statement)

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“…They observed six-fold degenerate spin states because of dipolar interaction [21]. Bailly-Reyre et al found ground-state configuration to be a vortex in the cubic assembly of nanodots [22]. Luttinger et al observed the minimum energy configurations to be ferromagnetic in a face-centred cubic lattice [23].…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%