Superparamagnetism in carbon-coated Co particles produced by the Kratschmer carbon arc process

McHenry, M. E.; Majetich, Sara A.; Artman, J. O.; DeGraef, Marc; Staley, Stuart W.

doi:10.1103/physrevb.49.11358

Cited by 269 publications

(127 citation statements)

References 17 publications

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“…Planar graphene is synthesized by this process on bulk crystals or thin films of transition metals, such as Ru [16][17][18], Pt [19], Ir [20], and Ni [21], which can take up carbon into interstitial sites with solubilities up to a few atomic percent. Carbon nanostructures, such as fullerenes [22][23][24][25] are synthesized over transition metal (Fe, Ni, Co) nanoparticles, using the same steps of hydrocarbon dissociation, carbon intake into interstitial sites, and precipitation. It is generally assumed that the uptake of carbon in metal nanoparticles involves interstitial sites, similar to the bulk, but the stable concentrations (i.e., the carbon solubility) may be different at the nanoscale.…”

mentioning

confidence: 99%

Giant carbon solubility in Au nanoparticles

Sutter

2011

J Mater Sci

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Variable temperature transmission electron microscopy of individual 5 nm Au nanoparticles shows a striking increase in the particle size on raising the temperature from room temperature to 500°C in the presence of carbon from amorphous carbon support. Using the assembly of ordered graphene shells on the surface of individual nanoparticles at elevated temperatures-and the high pressures induced by such shells-as an experimental tool to study the origins of this swelling, we find that the volume increase is associated with the uptake of carbon to concentrations exceeding the bulk solubility by more than four orders of magnitude. The formation of stable metalcarbon nanostructures that have no bulk equivalent may have important implications on the functional properties of metal nanoparticles.The interaction of carbon with transition metals is key to processes for synthesizing the known sp 2 bonded carbon allotropes-fullerenes, nanotubes, and graphene-all of which are materials showing extraordinary properties and enormous potential for applications.Graphene, a planar two-dimensional honeycomb lattice of sp 2 bonded carbon atoms [1] Typically, transition metals catalytically dissociate hydrocarbons at their surfaces to set free carbon adatoms, which can be absorbed into the bulk at high temperature and segregate to the surface on subsequent cooling to form sp 2 -bonded structures. Planar graphene is synthesized by this process on bulk crystals or thin films of transition metals, such as Ru [16][17][18], Pt [19], Ir [20], and Ni [21], which can take up carbon into interstitial sites with solubilities up to a few atomic percent. Carbon nanostructures, such as fullerenes [22][23][24][25] are synthesized over transition metal (Fe, Ni, Co) nanoparticles, using the same steps of hydrocarbon dissociation, carbon intake into interstitial sites, and precipitation. It is generally assumed that the uptake of carbon in metal nanoparticles involves interstitial sites, similar to the bulk, but the stable concentrations (i.e., the carbon solubility) may be different at the nanoscale. The high surface-to-volume ratio of nanoparticles has been predicted to cause a significant increase of the solubility [26][27][28][29][30][31][32][33]. However, lattice relaxation in very small particles Electronic supplementary material The online version of this article

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confidence: 99%

Giant carbon solubility in Au nanoparticles

Sutter

2011

J Mater Sci

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“…A linear dependence can be derived appreciably. On the contrary, if we assume that the temperature dependent coercivity is originated from Co clusters, we may estimate the cluster diameter according to the equation (McHenry et al, 1994):…”

Section: Field Dependent Magnetizationmentioning

confidence: 99%

“…The coercive field as a function of square root of temperature is delineated in the inset of Fig. 14. The data are fitted according to the equation (McHenry et al, 1994):…”

Section: Field Dependent Magnetizationmentioning

confidence: 99%

Characterization of Room-Temperature Ferromagnetic Zn1-xCoxO Nanowires

Ou¹,

Wu²,

Chen³

et al. 2010

Nanowires

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“…This holds true by neglecting other anisotropy contributions that could arise from the shape anisotropy (deviation from a spherical symmetry) and surface anisotropy, which would orient the magnetization into the plane of the surface and thereby create a disordered surface region with a reduced magnetization (spin-glass behaviour). Therefore, for an M -H measurement taken over a certain experimental time frame, the blocking temperature should satisfy the relationship (McHenry et al 1994)…”

Section: Measurement and Calculation Of The Blocking Temperaturementioning

confidence: 99%

Detection of endogenous magnetic nanoparticles with a tunnelling magneto resistance sensor

Ionescu

Darton

Vyas

et al. 2010

Phil. Trans. R. Soc. A.

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The magnetotactic bacterium Magnetospirillum sp. has been cultured and the properties of its endogenous magnetic nanoparticles characterized. Electron-microscopic analyses indicate that the endogenous magnetite nanoparticles in Magnetospirillum sp. are coated with a 3-4 nm thick transparent shell, forming a magnetosome. These magnetite nanoparticles had diameters of 50.9 ± 13.3 nm, in good agreement with the diameter of 40.6 ± 1.2 nm extracted from magnetometry. Each Magnetospirillum sp. bacterium contained chains of 5-25 magnetosomes. Superconducting quantum interference device magnetometry results indicate that the extrinsic superparamagnetic response of the bacterial solution at room temperature can be attributed to the reversal of the magnetization by physical rotation of the nanoparticles. The intrinsic blocking temperature of a sample of freeze-dried bacteria was estimated to be 282 ± 13 K. A tunnelling magneto resistance sensor was used to detect the stray fields of endogenous magnetic nanoparticles in static and quasi-dynamic modes. Based on the tunnelling magneto resistance sensor results, the magnetic moment per bacterium was estimated to be approximately 2.6 × 10 −13 emu. The feasibility of this detection method either as a mass-coverage device or as part of an integrated microfluidic circuit for detection and sorting of magnetosome-containing cells was demonstrated.

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Superparamagnetism in carbon-coated Co particles produced by the Kratschmer carbon arc process

Cited by 269 publications

References 17 publications

Giant carbon solubility in Au nanoparticles

Giant carbon solubility in Au nanoparticles

Characterization of Room-Temperature Ferromagnetic Zn1-xCoxO Nanowires

Detection of endogenous magnetic nanoparticles with a tunnelling magneto resistance sensor

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