Magnetic Properties of Cluster Glassy Ni/NiO Core–Shell Nanoparticles: an Investigation of Their Static and Dynamic Magnetization

Ji, Jhong-Yi; Shih, Po-Hsun; Chan, Ting‐Shan; Ma, Yuan‐Ron; Wu, Sheng Yun

doi:10.1186/s11671-015-0925-0

Cited by 29 publications

(12 citation statements)

References 38 publications

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“…Nanoscale magnetic materials often exhibit novel properties, differing from those of their bulk polycrystalline counterparts [1–5], as a result of several effects including the finite size effect, surface effect, and interparticle interaction [6–8]. These effects affect the magnetic properties and the magnetic ordering state of nanoparticles (NPs) individually, and sometimes synergetically which usually occurs in the dense magnetic NPs.…”

Section: Introductionmentioning

confidence: 99%

The remanence ratio in CoFe2O4 nanoparticles with approximate single-domain sizes

Geng

et al. 2016

Nanoscale Res Lett

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Approximately single-domain-sized 9-, 13-, and 16-nm CoFe2O4 nanoparticles are synthesized using the thermal decomposition of a metal-organic salt. By means of dilution and reduction, the concentration, moment, and anisotropy of nanoparticles are changed and their influence on the magnetic properties is investigated. The relation of M r/M s ∝ 1/lgH dip is observed, where M r/M s is the remanence ratio and H dip is the maximum dipolar field. Especially, such relation is more accurate for the nanoparticle systems with higher concentration and higher moment, i.e., larger H dip. The deviation from M r/M s ∝ 1/lgH dip appearing at low temperatures can be attributed to the effects of surface spins for the single-phase CoFe2O4 nanoparticles and to the pinning effect of CoFe2O4 on CoFe2 for the slightly reduced nanoparticles. Graphical AbstractApproximately single-domain-sized 9-, 13-, and 16-nm CoFe2O4 nanoparticles were synthesized and then the concentration, moment, and anisotropy of these NPs were changed. The correlation of M r/M s ∝ 1/lgH dip was observed, independent of the size, concentration, moment, and anisotropy, and especially, such correlation is more accurate for the nanoparticle systems with higher concentration or moment, i.e., stronger dipolar interaction, which has not been reported before as far as we know.

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Section: Introductionmentioning

confidence: 99%

The remanence ratio in CoFe2O4 nanoparticles with approximate single-domain sizes

Geng

et al. 2016

Nanoscale Res Lett

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“…Below a critical size of ~10 nm, as a consequence of the enhanced nickel vacancies, the Ni 2+ –O 2− –Ni 2+ superexchange interaction breaks down and the particles exhibit paramagnetic behavior at room temperature and superparamagnetic properties at lower temperature [11, 12]. The observed conventional exchange bias in Ni/NiO nanoparticles has been explained in a previous report by using a core/shell model with a higher concentration of nickel vacancies residing on the surface than in the core [7, 8]. The field-cooling hysteresis loop has also been shown to shift vertically when measured below the freezing temperature ( T f ) [8], which can be assigned as due to the interfacial frozen spins originating from the strong pinning effect between Ni and NiO [13].…”

Section: Introductionmentioning

confidence: 94%

“…Many of the above applications are based on the magnetic properties of the nanostructures, which vary with the synthesis method [7, 8], interparticle interaction [9], vacancies [10], and nanoparticle size [11], and show a pronounced effect on the magnetic properties of NiO nanoparticles. NiO, which is antiferromagnetic in its bulk form, exhibits ferromagnetic behavior at the nanoscale due to nickel vacancy defects, with its net magnetic moment increasing monotonically with decreasing particle size [7, 8]. Below a critical size of ~10 nm, as a consequence of the enhanced nickel vacancies, the Ni 2+ –O 2− –Ni 2+ superexchange interaction breaks down and the particles exhibit paramagnetic behavior at room temperature and superparamagnetic properties at lower temperature [11, 12].…”

Section: Introductionmentioning

confidence: 99%

Strong Pinned-Spin-Mediated Memory Effect in NiO Nanoparticles

et al. 2017

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After a decade of effort, a large number of magnetic memory nanoparticles with different sizes and core/shell compositions have been developed. While the field-cooling memory effect is often attributed to particle size and distribution effects, other magnetic coupling parameters such as inter- and intra-coupling strength, exchange bias, interfacial pinned spins, and the crystallinity of the nanoparticles also have a significant influence on magnetization properties and mechanisms. In this study, we used the analysis of static- and dynamic-magnetization measurements to investigate NiO nanoparticles with different sizes and discussed how these field-cooling strengths affect their memory properties. We conclude that the observed field-cooling memory effect from bare, small size NiO nanoparticles arises because of the unidirectional anisotropy which is mediated by the interfacial strongly pinned spins.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-1988-x) contains supplementary material, which is available to authorized users.

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“…Nickel oxide, which is an antiferromagnetic material, has been reported to display ferromagnetic characteristics as nanoparticles, probably due to the nickel vacancies, with the magnetic moment increasing with decreasing particle size [14,15]. Below a size of about 10 nm, the Ni 2+ -O 2− -Ni 2+ super exchange interaction breaks down (possibly due to the presence of more nickel vacancies) and the nanoparticles exhibit paramagnetic behavior.…”

Section: Nickel Oxidementioning

confidence: 99%

Effects of Precursor Concentration in Solvent and Nanomaterials Room Temperature Aging on the Growth Morphology and Surface Characteristics of Ni–NiO Nanocatalysts Produced by Dendrites Combustion during SCS

et al. 2019

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The morphology and surface characteristics of SCS(Solution Combustion Synthesis)-derived Ni–NiO nanocatalysts were studied. The ΤΕΜ results highlighted that the nanomaterial’s microstructure was modified by changing the reactants’ concentrations. The dendrites’ growth conditions were the main factors responsible for the observed changes in the nanomaterials’ crystallite size. Infrared camera measurements demonstrated a new type of combustion through dendrites. The XPS analysis revealed that the NiO structure resulted in the bridging of the oxygen structure that acted as an inhibitor of hydrogen adsorption on the catalytic surface and, consequently, the activity reduction. The RF-IGC indicated three different kinds of active sites with different energies of adsorption on the fresh catalyst and only one type on the aged catalyst. Aging of the nanomaterial was associated with changes in the microstructure of its surface by a gradual change in the chemical composition of the active centers.

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Magnetic Properties of Cluster Glassy Ni/NiO Core–Shell Nanoparticles: an Investigation of Their Static and Dynamic Magnetization

Cited by 29 publications

References 38 publications

The remanence ratio in CoFe2O4 nanoparticles with approximate single-domain sizes

The remanence ratio in CoFe2O4 nanoparticles with approximate single-domain sizes

Strong Pinned-Spin-Mediated Memory Effect in NiO Nanoparticles

Effects of Precursor Concentration in Solvent and Nanomaterials Room Temperature Aging on the Growth Morphology and Surface Characteristics of Ni–NiO Nanocatalysts Produced by Dendrites Combustion during SCS

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