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Hiroi, Kosuke; Komatsu, Katsuyoshi; Sato, Tetsuya

doi:10.1103/physrevb.83.224423

Cited by 98 publications

(54 citation statements)

References 41 publications

(51 reference statements)

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“…Here, τ * is a relaxation time for each nanoparticle, zν is the dynamical scaling-critical exponent constant [31] related to the correlation length ξ. In in Figure 7 we plot the variation of τ m (in log scale) with T AC max .…”

Section: Resultsmentioning

confidence: 99%

Exchange-bias-like coupling in a Cu-diluted-Fe/Tb multilayer

et al. 2015

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Transition metal-rare earth (TM-RE) Fe/Tb-multilayer systems have been known to show exchange-bias-like shifts in the form of double hysteresis loop (DHL) along and opposite to the field cooling axis. Planar domain walls (DW), with opposite handedness at the interfaces, are held responsible for such DHL. Here, we report on the formation of nanoparticulated Fe layers in the Cu-matrix within a Fe-Cu/Tb multilayer and their eventual low temperature characteristics. AC susceptibility measurements indicate that these diluted magnetic clusters have a superspin-glass type of freezing behavior. Eventually, this Fe-cluster/Tb interlayer interaction, which is conjectured to be mediated by the pinned moments within the individual clusters, has helped in increasing the exchange bias field in the system to a high value of ≈1.3 kOe which gradually vanishes around 50 K. Polarized neutron reflectivity confirms a very strong antiferromagnetic (AF) coupling between the individual layers. The magnitude of the magnetic moment of each of the individual Tb or Fe-Cu layer remains similar but due to the strong AF-coupling at the interfaces, the entire ferrimagnetic Fe-Cu/Tb entity flips its direction at a compensation field of around 3.7 kOe. This study shows that magnetic dilution can be an effective way to manipulate the possible domain walls or the clusters in TM and thereby the exchange bias in TM-RE systems.

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Section: Resultsmentioning

confidence: 99%

Exchange-bias-like coupling in a Cu-diluted-Fe/Tb multilayer

et al. 2015

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“…Similarly, a shift toward a higher temperature for the maximum of the zero field-cooled magnetization curve and a reduced coercivity at low temperature have been observed for systems that adopt a raised volume fraction (ϕ) for the inorganic magnetic phase [110] or even when the morphology [111,112] allows for very short distances between particles; all such postulate to the presence of dipole-dipole interactions. The nanocrystals were found to be non-interacting when the distance between them exceeds 47 nm [112]. Literature results on various types of nanocrystal assemblies in which their magnetic behavior is governed by dipoledipole interactions, motivate us to explore further such inter-particle interactions so that technologically useful nanomaterials can be realized.…”

Section: The Role Of Dipole-dipole Interactionsmentioning

confidence: 99%

“…Such an increase in the attempt time, when dipolar interactions become stronger, is in agreement with earlier reports concerned with individual nanoparticles. In one such case, the dipolar interaction strength was tuned by modifying the shell thickness of γ-Fe 2 O 3 @SiO 2 core-shell nanocrystals [112] while in another example by increasing the inorganic particle volume fraction within a frozen ferrofluid of Fe-C nanocrystals [116].…”

Section: The Role Of Dipole-dipole Interactionsmentioning

confidence: 99%

Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages

Κωστοπούλου

Lappas

2015

Nanotechnology Reviews

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Magnetic particles of optimized nanoscale dimensions can be utilized as building blocks to generate colloidal nanocrystal assemblies with controlled size, well-defined morphology, and tailored properties. Recent advances in the state-of-the-art surfactant-assisted approaches for the directed aggregation of inorganic nanocrystals into cluster-like entities are discussed, and the synthesis parameters that determine their geometrical arrangement are highlighted. This review pays attention to the enhanced physical properties of iron oxide nanoclusters, while it also points to their emerging collective magnetic response. The current progress in experiment and theory for evaluating the strength and the role of intra-and inter-cluster interactions is analyzed in view of the spatial arrangement of the component nanocrystals. Numerous approaches have been proposed for the critical role of dipole-dipole and exchange interactions in establishing the nature of the nanoclusters' cooperative magnetic behavior (be it ferromagnetic or spin-glass like). Finally, we point out why the purposeful engineering of the nanoclusters' magnetic characteristics, including their surface functionality, may facilitate their use in diverse technological sectors ranging from nanomedicine and photonics to catalysis.

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“…Such clusters were recently proposed for addressing the challenge of inverse engineering in self-assembled systems 1,2 . From a functional perspective, designed meso-clusters from nanoparticles (NP) are attractive for accessing their collective and synergetic effects 3–6 and manipulating their optical response 3,7–9 .…”

mentioning

confidence: 99%

Prescribed nanoparticle cluster architectures and low-dimensional arrays built using octahedral DNA origami frames

et al. 2015

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Reliably creating three-dimensional (3D) mesoscale clusters, in which nanoparticles are spatially arranged in pre-determined positions, is the first step towards arbitrarily designed self-assembled architectures. These engineered clusters would be the mesoscale analogs of molecules and would thus offer tailored nanoparticles properties due to the collective effects. However, establishing a flexible and broadly applicable platform for the fabrication of nanoparticles architectures, as well as probing their 3D non-periodic organizations, is challenging. Here we report a novel strategy for assembling 3D nanoparticle clusters: designing a molecular frame with encoded vertices for particles placement. By positioned specific particles types at the vertices of such frame, a DNA origami octahedron, we fabricated clusters of various symmetries and particles composition. We applied the Cryo-EM methods to uncover the DNA frame structure, and to reveal that nanoparticles are spatially coordinated in the prescribed manner. Employing the demonstrated assembly strategy, we have created nanoclusters with different chiroptical activities based on the specifically encoded center-symmetrical DNA frame and the same set of nanoparticles. We also show that octahedra with particularly selected vertices can serve as tailorable interparticle linker with a certain geometry of interparticle connections, thus, allowing for assembly of 1D or 2D arrays with designed particle arrangements.

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Superspin glass originating from dipolar interaction with controlled interparticle distance amongγ-Fe2O

Cited by 98 publications

References 41 publications

Exchange-bias-like coupling in a Cu-diluted-Fe/Tb multilayer

Exchange-bias-like coupling in a Cu-diluted-Fe/Tb multilayer

Colloidal magnetic nanocrystal clusters: variable length-scale interaction mechanisms, synergetic functionalities and technological advantages

Prescribed nanoparticle cluster architectures and low-dimensional arrays built using octahedral DNA origami frames

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