Relaxation Times in Magnetic Nanoparticles System and Memory Effects

Osaci, Mihaela; Abrudean, C.; Berdie, Adela Diana

doi:10.12693/aphyspola.112.1203

Cited by 10 publications

(4 citation statements)

References 15 publications

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“…Consequently, the magnetic moments associated with nanoparticles tend to align ferromagnetically along the long axis, resulting in a slowing down of magnetic relaxation. The slowing down of magnetic relaxation with h d is in qualitative agreement with the work of Osaci et al [49]. The strength of shape anisotropy or ferromagnetic coupling also gets enhanced with h d and ∆.…”

Section: Simulations Resultssupporting

confidence: 90%

Disorder-Induced Complex Magnetization Dynamics in Planar Ensembles of Nanoparticles

Anand¹

2021

Preprint

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The magnetic relaxation characteristics are investigated in the two-dimensional (l x ×l y ) assembly of nanoparticles as a function of out-of-plane positional disorder strength ∆(%) using numerical simulations. Such defects are redundantly observed in experimentally fabricated nanostructures, resulting in unusual magnetization dynamics. The magnetization decays exponentially for small and negligible dipolar interaction strength h d ≤ 0.2. In such a case, the magnetization relaxation does not depend on ∆ and aspect ratio A r = l y /l x , as expected. In square-like MNPs ensembles and perfectly ordered system (∆(%) = 0), the magnetization relaxes rapidly with an increase in h d . Consequently, the effective Néel relaxation time τ N decreases with h d . The dipolar interaction of sufficient strength promotes antiferromagnetic coupling in such a system, resulting in rapid magnetization decay. Remarkably, the out-of-plane disorder instigates the magnetic moment to interact ferromagnetically in the presence of large h d , even in the square-like assembly of MNPs.As a result, magnetization relaxation slows down, resulting in a monotonous increase of τ N with an increase in ∆ and h d in such cases. Notably, there is a prolonged magnetization decay in the highly anisotropic system with large h d . The dipolar interaction induces ferromagnetic coupling along the long axis of the system in such cases. Therefore, the magnetization ceases to relax as a function of time for large h d , irrespective of disorder strength ∆(%). The present work could provide a concrete theoretical basis to explain the unexpected relaxation behaviour observed in experiments.These results are also beneficial in digital data storage and spintronics based applications where such nanostructures are extensively used.

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Section: Simulations Resultssupporting

confidence: 90%

Disorder-Induced Complex Magnetization Dynamics in Planar Ensembles of Nanoparticles

Anand¹

2021

Preprint

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“…In the case of a system, having "memory" effects and/or long-range correlations, such as nonthermal noise, may also occur. 23 Tails of distribution curves of delay time follow power law 24 PðlÞ ≈ l −μ ;…”

Section: Resultsmentioning

confidence: 99%

Levy distribution of time delay in emission of resonantly trapped light in ferrodispersions

Patel

Mehta

2012

J. Nanophoton

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“…The lower relaxation time is also associated with an increase in the concentration of nanoparticles in Fe 3 O 4 -SiO 2 [7]. The decrease in relaxation time in Fe 3 O 4 , after being encapsulated with SiO 2, can also be related to changes in the anisotropic energy value of the nanoparticles, where the anisotropic energy is also related to the blocking temperature [8,14,20,21]. In our previous study, it was reported that the anisotropic energy of the nanoparticles increased when the Fe 3 O 4 samples were encapsulated with SiO 2 .…”

Section: Magnetic Relaxation Time 𝑀(𝑡)mentioning

confidence: 99%

Study of Magnetic Properties and Relaxation Time of Nanoparticle Fe3O4-SiO2

et al. 2022

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The magnetic properties and relaxation time of Fe3O4 nanoparticles, and their encapsulation with silicon dioxide (Fe3O4-SiO2), have been successfully investigated by analyzing the temperature dependence of magnetization (()) and the time dependence of magnetization (()), using the SQUID magnetometer measurement. The () measurement results can determine the magnetic parameters and magnetic irreversibility of Fe3O4 and Fe3O4-SiO2 samples. The values of Curie constant (), effective magnetic moment (), and Weiss temperature () are 4.2 (emu.K.Oe/mol), 5.77 , and −349 K, respectively, for the Fe3O4 samples, and 81.3 (emu.K.Oe/mol), 25.49 , and −2440 K, respectively, for the Fe3O4-SiO2 samples. After encapsulation, the broadening peak deviation decreased from 281.6 K to 279 K, indicating that the superparamagnetic interactions increased with the encapsulation process. The magnetic parameters and irreversibility values showed that the superparamagnetic properties increased significantly after encapsulation (Fe3O4-SiO2). From the results of the () measurement, it was found that there was a decrease in the magnetic relaxation time after the encapsulation process, which indicated that the distribution of the nanoparticle size and anisotropy energy increased.

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Relaxation Times in Magnetic Nanoparticles System and Memory Effects

Cited by 10 publications

References 15 publications

Disorder-Induced Complex Magnetization Dynamics in Planar Ensembles of Nanoparticles

Disorder-Induced Complex Magnetization Dynamics in Planar Ensembles of Nanoparticles

Levy distribution of time delay in emission of resonantly trapped light in ferrodispersions

Study of Magnetic Properties and Relaxation Time of Nanoparticle Fe3O4-SiO2

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