Effect of dipolar interaction observed in iron-based nanoparticles

Vargas, J. M.; Nunes, Wallace C.; Socolovsky, L.M.; Knobel, M.; Zanchet, Daniela

doi:10.1103/physrevb.72.184428

Cited by 207 publications

(163 citation statements)

References 37 publications

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“…11,12 Competing interactions between magnetic particles can also modify the magnetic features of nanosystem. 13,14 For instance, interparticle interactions in concentrated nanoparticle systems can affect the height and distribution of the energy barriers. Interactions between particles may imply an increase in the average blocking temperature in both ac-and dc-magnetization measurements.…”

Section: Introductionmentioning

confidence: 99%

“…19 In the last years, effects of interactions on the magnetic relaxation in systems presenting such superspin-glass state have been studied using ac-susceptibility measurements. 13,20 Recently, some examples have shown the effects of such SSG state also in dc-magnetothermal curves. Sahoo et al 18 show an AT dependence of the blocking temperatures of discontinuous ͓Co 80 Fe 20 ͑0.9 nm͒ / Al 2 O 3 ͑3 nm͔͒ multilayers, observed by zero-field-cooling-field-cooling ͑ZFC-FC͒ magnetothermal curves at very weak fields ͑H Ͻ 50 Oe͒, with a destruction of the AT behavior at intermediate fields, proposing a crossover into a chiral glass regime.…”

Section: Introductionmentioning

confidence: 99%

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Effects of interparticle interactions in magneticFe/Si3N4granular systems

et al. 2010

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An experimental evidence of the progressive modification in the magnetic behavior of granular Fe/ Si 3 N 4 samples due to interaction effects between particles is reported. Microstructural features and local structure were determined by x-ray absorption spectroscopy and transmission electron microscopy to select granular samples with predetermined cluster size. Fe/ Si 3 N 4 systems have been characterized by ac-and dcmagnetization measurements to study the gradual evolution of magnetic properties of granular systems, where three different behaviors have been observed. As-deposited samples with Fe thickness layers of 2.5 nm, present a modified superparamagnetic behavior, due to very weak interactions between very small Fe clusters separated by a nonmagnetic FeN phase. An evolution of the average blocking temperature at intermediate fields ͑T B ϳ H 3/2 ͒ is observed, similar to noninteracting systems, but first signatures of a frozen spin state at low temperatures appear. Annealed samples exhibit a noticeable modification from the multilayer character to a random three-dimensional organization of Fe clusters embedded in a Si 3 N 4 matrix. After annealing, samples with initial Fe layer thickness of 0.7 nm provide iron cluster in the range of 1.3 nm and exhibit a superspinglass state, with a de Almeida-Thouless evolution of the energy barriers ͑T B ϳ H 2/3 ͒ that is explained in terms of increasing interparticle interactions. Moreover, annealed samples, with initial layer thickness of 1.3 nm, supply iron cluster of near 3 nm that present stronger interactions and yield a superferromagnetic state, likely provided by residual ultrasmall particles between the blocked clusters.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of interparticle interactions in magneticFe/Si3N4granular systems

et al. 2010

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“…In this present system, the deviation from Langevin functions is due to strong magnetic dipole interaction. 7,13 The T* model has been …”

Section: -5mentioning

confidence: 99%

“…This is because the distance between the Fe NPs in the FNAs is smaller by annealing and molding than that of the isolated state; therefore, the magnetic dipole interaction in each FNA cannot be ignored. 7,[13][14][15] However, in the FNA fabricated with 4.3 nm diameter Fe NPs, the effect of thermal fluctuation is stronger than that of the magnetic dipole interaction. Therefore, the FNA fabricated with 4.3 nm diameter Fe NPs shows superparamagnetic behavior under moderate magnetic dipole interaction at room temperature.…”

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confidence: 99%

Core loss and magnetic susceptibility of superparamagnetic Fe nanoparticle assembly

2016

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Toroidal-shaped high-density Fe nanoparticle assemblies (FNAs) were fabricated by molding different sized Fe nanoparticles (NPs), and the effect of the magnetic behavior of the FNAs on the core loss and the magnetic susceptibility was investigated. An FNA with 4.3 nm diameter Fe NPs exhibits superparamagnetism at room temperature while an FNA with 6.4 nm diameter Fe NPs doesn’t exhibit superparamagnetism at room temperature. AC magnetization curves at 1, 10 and 100 kHz were measured to evaluate the core loss of the toroidal-shaped FNAs. Both FNAs exhibited no significant eddy current loss, which suggests that surfactants on the NP surface effectively act to electrically insulate the NPs, and the NPs are not sintered together when the FNAs are molded. The AC magnetization curves had no hysteresis for the FNA with 4.3 nm diameter Fe NPs, i.e., the core loss was minimal for the superparamagnetic FNA. The magnetic susceptibility of the superparamagnetic FNA with 4.3 nm Fe NPs was 12 times higher than that estimated from Langevin theory due to the effect of strong magnetic dipole interaction. These results suggest that the superparamagnetic FNA has potential as a magnetic core material that exhibits low core loss and high magnetic susceptibility, even at high frequency.

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“…2.1, 3.1 and 5.1, that the nickel nanoparticles are agglomerated and, being in close proximity, strong magnetic dipolar interactions may be present. These are known to enhance blocking temperatures [29,30] and also give rise to a 'flattening' of the FC curve below T B which may otherwise be interpreted as a consequence of a narrow particle size distribution [31]. Thus it may be that both an enhancement of the surface magnetocrystalline anisotropy and inter-particle dipolar interactions are responsible for the enhanced values of T B in samples 1, 2 and 4.…”

Section: Samples 1 2 Andmentioning

confidence: 99%

Controlling nickel nanoparticle size in an organic/metal–organic matrix through the use of different solvents

2013

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(2013) 'Controlling nickel nanoparticle size in an organic/metal-organic matrix through the use of di erent solvents. ', Nanoscale., 5 (24). pp. 12212-12223. Further information on publisher's website:http://dx.doi.org/10.1039/c3nr04883gPublisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. (0) atoms from the Ni(COD)2. Materials are characterised with a combination of X-ray diffraction, electron microscopy and magnetometry and it is found that samples made using a halocarbon solvent resulted in clustered bulk Ni particles (size ≤ 10 nm) with anomalously high superparamagnetic blocking temperatures. Using an isocyanide solvent produces smaller (size ∼ 1 nm), well dispersed particles that show little evidence of superparamagnetic blocking in the range of temperatures investigated (> 2 K). In all samples there is another component which dominates the magnetic response at low temperatures and shows an interesting temperature dependent scaling behaviour when plotted as M vs B/T which we believe is related to the organo-metallic matrix that the particles are trapped within. We propose that the enhanced blocking temperature of particles synthesised using halocarbon solvents can be attributed to inter-particle dipolar interactions and nanoparticle-matrix exchange interactions.

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Effect of dipolar interaction observed in iron-based nanoparticles

Cited by 207 publications

References 37 publications

Effects of interparticle interactions in magneticFe/Si3N4granular systems

Effects of interparticle interactions in magneticFe/Si3N4granular systems

Core loss and magnetic susceptibility of superparamagnetic Fe nanoparticle assembly

Controlling nickel nanoparticle size in an organic/metal–organic matrix through the use of different solvents

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