Dipole interactions with random anisotropy in a frozen ferrofluid

Luo, Weili; Nagel, Sidney R.; Rosenbaum, T. F.; Rosensweig, Ronald E.

doi:10.1103/physrevlett.67.2721

Cited by 458 publications

(386 citation statements)

References 28 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12] An assembly of magnetic nanoparticles is, in general, a disordered system with random anisotropy and competing interparticle interactions. 12 In a very diluted system, i.e., where interparticle dipole-dipole interactions are negligibly small in comparison with anisotropy energy, the dynamics of particles are well described by the superparamagnetism framework of the Néel-Brown model.…”

Section: Introductionmentioning

confidence: 99%

“…Most studies on how dipole-dipole interactions lead to SGL phase in particles systems were carried out by changing the concentration of particles ͑particle-particle distance͒ in the liquid carrier. [1][2][3][4][5][6][7][8][9][10][11]14 Here, we studied the same issue by changing the particle ͑or cluster͒ size and the concentration of solute Co atoms in Ag matrix. We focused on the study of memory effect because it is usually considered as typical characteristics of the spinglass dynamics and has been clearly observed in different ͑canonical͒ spin-glass systems.…”

Section: Introductionmentioning

confidence: 99%

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Memory effect and spin-glass-like behavior in Co-Ag granular films

Zhang

Zheng

et al. 2007

Phys. Rev. B

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The memory effect was clearly observed in dc-sputtered metallic, magnetic Co-Ag granular films, which indicates the existence of a spin-glass-like phase at low temperatures. However, the memory effect diminished dramatically after the films were annealed at 300°C for 1 h. It was also found that the memory effect weakened gradually with increasing volume fraction of magnetic clusters. The experimental results indicate that the dipolar interaction is not the major origin for the formation of low-temperature spin-glass-like ͑SGL͒ phase in metallic, magnetic granular materials. On the other hand, a Ruderman-Kittel-Kasuya-Yosida-like exchange interaction between the nanoparticles may be responsible for the collective SGL dynamics and the resulting memory effect.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Memory effect and spin-glass-like behavior in Co-Ag granular films

Zhang

Zheng

et al. 2007

Phys. Rev. B

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“…Moreover, it can be seen from the TEM results that the sizes of the nanoparticles derived from the LDH precursor are much smaller than those obtained from the precursor prepared by the coprecipitation method and are strongly clustered with each other, giving a larger effective AFM NiO phase "thickness" around the NiFe 2 O 4 nanoparticles. Furthermore, when the particles are clustered together, due to the exchange coupling effect in the NiO phase around different NiFe 2 O 4 nanoparticles, they exert a "collective behavior" and thus have an extra effective AFM "thickness" which further increases the blocking temperature of the NiFe 2 O 4 nanoparticles [44,45].…”

Section: Blocking Temperature Of Nife 2 O 4 /Nio Nanocomposites and Mmentioning

confidence: 99%

Exchange-biased NiFe2O4/NiO nanocomposites derived from NiFe-layered double hydroxides as a single precursor

Zhao

Wang

et al. 2010

Nano Res.

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NiFe 2 O 4 nanoparticles (<10 nm) embedded in a NiO matrix have been fabricated by calcining the corresponding Ni Ⅱ Fe Ⅲ -layered double hydroxide (LDH) precursors at high temperature (500 °C ). Compared with the NiFe 2 O 4 /NiO nanocomposite obtained by calcination of a precursor prepared by a traditional chemical coprecipitation method, those derived from NiFe-LDH precursors show much higher blocking temperatures (T B ) (~380 K). The enhanced magnetic stability can be ascribed to the much stronger interfacial interaction between NiFe 2 O 4 and NiO phases due to the topotactic nature of the transformation of the LDH precursor to the NiFe 2 O 4 /NiO composite material. Through tuning the Ni Ⅱ /Fe Ⅲ molar ratio of the NiFe-LDH precursor, the NiFe 2 O 4 concentration can be precisely controlled, and the T B value as well as the magnetic properties of the final material can also be regulated. This work represents a successful example of the fabrication of ferro(ferri)magnetic (FM)/antiferrimagnetic (AFM) systems with high magnetic stability from LDH precursors. This method is general and may be readily extended to other FM/AFM systems due to the wide range of available LDH precursors.

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“…Interactions between particles may imply an increase in the average blocking temperature in both ac-and dc-magnetization measurements. 15,16 It has been stated that a transition from superparamagnetic ͑SPM͒ to spin-glasslike behaviors, or even to superferromagnetism ͑SFM͒, can be due to interactions between superspins ͑magnetic moments of the ferromagnetic nanoparticles͒. 17,18 As an open question, one of the main challenges is to elucidate the contributions of dipolar, exchange and tunneling exchange interactions, as well as to distinguish the contributions to the effective barrier distribution of dipolar interactions and surface spin frustration.…”

Section: Introductionmentioning

confidence: 99%

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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Dipole interactions with random anisotropy in a frozen ferrofluid

Abstract: Glassy behavior (including hysteresis, irreversibility, a peak in the zero-field-cooled magnetization, and nonexponential relaxation) is observed in a quenched ferrofluid system consisting of 50-A magnetite particles. An

Cited by 458 publications

References 28 publications

Memory effect and spin-glass-like behavior in Co-Ag granular films

Memory effect and spin-glass-like behavior in Co-Ag granular films

Exchange-biased NiFe2O4/NiO nanocomposites derived from NiFe-layered double hydroxides as a single precursor

Effects of interparticle interactions in magneticFe/Si3N4granular systems

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