Mesoscopic Model for the Simulation of Large Arrays of Bi‐Magnetic Core/Shell Nanoparticles

Margaris, G.; Trohidou, K. N.; Nogués, J.

doi:10.1002/adma.201200615

Cited by 44 publications

(47 citation statements)

References 37 publications

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“…[27,29,30,77,78,79]. In addition, different theoretical models and simulations have been developed in order to gain a better understanding of the role of different parameters that control the EB in these core/shell MNPs [5,40,80,81,82,83]. It has also been shown that both inter- and intra-particle interactions play important roles in the EB loop shift [73,74,75].…”

Section: Exchange Bias Effect In Core/shell Nanoparticlesmentioning

confidence: 99%

Exchange Bias Effects in Iron Oxide-Based Nanoparticle Systems

et al. 2016

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The exploration of exchange bias (EB) on the nanoscale provides a novel approach to improving the anisotropic properties of magnetic nanoparticles for prospective applications in nanospintronics and nanomedicine. However, the physical origin of EB is not fully understood. Recent advances in chemical synthesis provide a unique opportunity to explore EB in a variety of iron oxide-based nanostructures ranging from core/shell to hollow and hybrid composite nanoparticles. Experimental and atomistic Monte Carlo studies have shed light on the roles of interface and surface spins in these nanosystems. This review paper aims to provide a thorough understanding of the EB and related phenomena in iron oxide-based nanoparticle systems, knowledge of which is essential to tune the anisotropic magnetic properties of exchange-coupled nanoparticle systems for potential applications.

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Section: Exchange Bias Effect In Core/shell Nanoparticlesmentioning

confidence: 99%

Exchange Bias Effects in Iron Oxide-Based Nanoparticle Systems

et al. 2016

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“…This translates to an enhanced energy barrier to moment reversal, resulting in thermal stability of the spins even above T B and subsequent display of EB by the sample. In the context of our analysis of exchange bias above T B based on the proposed shell-shell interaction model, we mention that similar models have earlier been proposed in literature 16,17 to elucidate the radically enhanced magnetic stability of FM cores of core-shell FM-AFM nanoparticles in contact, as compared to when the NPs were isolated. The enhanced shell thickness when the NPs come into contact was proposed to recover the bulk AFM properties of the shell, leading to better interfacial coupling, large bias fields, and an increase in the blocking temperature of the cores.…”

Section: Exchange Bias Above T B :Analysismentioning

confidence: 99%

Exchange bias beyond the superparamagnetic blocking temperature of the antiferromagnet in a Ni-NiO nanoparticulate system

Roy

Toro

Amaral

et al. 2014

Journal of Applied Physics

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We report magnetic and exchange bias studies on Ni-NiO nanoparticulate systems synthesized by a two-step process, namely, chemical reduction of a Ni salt followed by air annealing of the dried precipitate in the temperature range 400 550 C. Size of Ni and NiO crystallites as estimated from X ray diffraction line broadening ranges between 10.5 13.5 nm and 2.3 4 nm, respectively. The magneto-thermal plots (M-T) of these bi-magnetic samples show a well developed peak in the vicinity of 130 K. This has been identified as the superparamagnetic blocking temperature "T B " of NiO. Interestingly, all samples exhibit exchange bias even above their respective NiO blocking temperatures, right up to 300 K, the maximum temperature of measurement. This is in contrast to previous reports since exchange bias requires the antiferromagnetic NiO to have a stable direction of its moment in order to pin the ferromagnet (Ni) magnetization, whereas such stability is unlikely above T B since the NiO is superparamagnetic, its moment flipping under thermal activation. Our observation is elucidated by taking into account the core-shell morphology of the Ni-NiO nanoparticles whereby clustering of some of these nanoparticles connects their NiO shells to form extended continuous regions of NiO, which because of their large size remain blocked at T > T B , with thermally stable spins capable of pinning the Ni cores and giving rise to exchange bias. The investigated samples may thus be envisaged as being constituted of both isolated core-shell Ni-NiO nanoparticles as well as clustered ones, with T B denoting the blocking temperature of the NiO shell of the isolated particles. V C 2014 AIP Publishing LLC. [http://dx

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“…This type of inverted structures overcomes some of the limitations of conventional systems, since the AFM structure (and thus its magnetic properties) can be much better controlled in the core than in the shell (where usually it is forced to grow in non-ideal conditions). It has been demonstrated, experimentally and theoretically, that the poor crystallinity of the AFM counterpart can result in considerably inferior exchange bias properties4344. In fact, inverted structures have already demonstrated very large coercivities and loop shifts, tunable blocking temperatures, enhanced Néel temperatures or proximity effects12131415161718192021222324252627282930313233343536373839404142 and have been proposed as potential magnetoelectric random access memories41.…”

mentioning

confidence: 99%

Enhanced Magnetic Properties in Antiferromagnetic-Core/Ferrimagnetic-Shell Nanoparticles

Vasilakaki

Trohidou

Nogués

2015

Sci Rep

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Bi-magnetic core/shell nanoparticles are gaining increasing interest due to their foreseen applications. Inverse antiferromagnetic(AFM)/ferrimagnetic(FiM) core/shell nanoparticles are particularly appealing since they may overcome some of the limitations of conventional FiM/AFM systems. However, virtually no simulations exist on this type of morphology. Here we present systematic Metropolis Monte Carlo simulations of the exchange bias properties of such nanoparticles. The coercivity, HC, and loop shift, Hex, present a non-monotonic dependence with the core diameter and the shell thickness, in excellent agreement with the available experimental data. Additionally, we demonstrate novel unconventional behavior in FiM/AFM particles. Namely, while HC and Hex decrease upon increasing FiM thickness for small AFM cores (as expected), they show the opposite trend for large cores. This presents a counterintuitive FiM size dependence for large AFM cores that is attributed to the competition between core and shell contributions, which expands over a wider range of core diameters leading to non-vanishing Hex even for very large cores. Moreover, the results also hint different possible ways to enhance the experimental performance of inverse core/shell nanoparticles for diverse applications.

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Mesoscopic Model for the Simulation of Large Arrays of Bi‐Magnetic Core/Shell Nanoparticles

Cited by 44 publications

References 37 publications

Exchange Bias Effects in Iron Oxide-Based Nanoparticle Systems

Exchange Bias Effects in Iron Oxide-Based Nanoparticle Systems

Exchange bias beyond the superparamagnetic blocking temperature of the antiferromagnet in a Ni-NiO nanoparticulate system

Enhanced Magnetic Properties in Antiferromagnetic-Core/Ferrimagnetic-Shell Nanoparticles

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