Highly enhanced orbital magnetism on cobalt cluster surfaces

Eastham, D.A.; Kirkman, I. W.

doi:10.1088/0953-8984/12/31/101

Cited by 26 publications

(14 citation statements)

References 22 publications

(36 reference statements)

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“…A possible explanation is suggested by measurements [19] of the orbital moments in the same cluster samples. There is evidence in these measurements of changes in the orbital moment as a function of the applied field.…”

Section: Resultsmentioning

confidence: 94%

Electrical Characteristics of Controlled-Polarization-Type Ferroelectric-Gate Field-Effect Transistor

Fukushima

Yoshimura

Masuko

et al. 2008

jjap

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The magnetic properties of nanomaterials made by embedding cobalt nanocrystals in a copper matrix have been studied using a SQUID magnetometer. The remanent magnetization at temperatures down to 1.8 K and the RT (room temperature) field-dependent magnetization of 1000-and 8000-atom (average-size) cobalt cluster samples have been measured. In all cases it has been possible to relate the morphology of the material to the magnetic properties. However, it is found that the deposited cluster samples contain a majority of sintered clusters even at cobalt concentrations as low as 5% by volume. The remanent magnetization of the 8000-atom samples was found to be bimodal, consisting of one contribution from spherical particles and one from touching (sintered) clusters. Using a Monte Carlo calculation to simulate the sintering it has been possible to calculate a size distribution which fits the RT superparamagnetic behaviour of the 1000-atom samples. The remanent magnetization for this average size of clusters could then be fitted to a simple model assuming that all the nanoparticles are spherical and have a size distribution which fits the superparamagnetic behaviour. This gives a value for the potential energy barrier height (for reversing the spin direction) of 2.0 µeV/atom which is almost four times the accepted value for face-centredcubic bulk cobalt. The remanent magnetization for the spherical component of the large-cluster sample could not be fitted with a single barrier height and it is conjectured that this is because the barriers change as a function of cluster size. The average value is 1.5 µeV/atom but presumably this value tends toward the bulk value (0.5 µeV/atom) for the largest clusters in this sample.

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Section: Resultsmentioning

confidence: 94%

Electrical Characteristics of Controlled-Polarization-Type Ferroelectric-Gate Field-Effect Transistor

Fukushima

Yoshimura

Masuko

et al. 2008

jjap

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“…Recently attention has focused on the behaviour of magnetic particles with sizes below 5 nm in which the fundamental spin and orbital moments deviate significantly from their bulk [1][2][3][4][5][6][7][8][9][10] values. Their novel behaviour arises from the high proportion of surface atoms ($30% for the clusters studied in this work), producing a narrowing of the d-band responsible for magnetism and an increase in the density of states at the Fermi level.…”

Section: Introductionmentioning

confidence: 99%

Magnetism in Fe Nanoclusters ? From Isolated Particles to Nanostructured Materials

Binns

Baker

Maher

et al. 2002

phys. stat. sol. (a)

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We have studied the evolution of the magnetic behaviour of Fe nanoclusters from isolated particles adsorbed on a surface and exposed in UHV to dense interacting assemblies. The clusters were produced by a UHV-compatible gas aggregation source and were studied in situ by synchrotron radiation techniques based on dichroism and ex situ after transfer into a UHV-capable vibrating sample magnetometer. Isolated and exposed 250-atom Fe clusters deposited on HOPG substrates exhibit enhanced orbital and spin magnetic moments that decay towards the bulk value with increasing size or with increasing particle density on the surface. The individual particles appear to be magnetically isotropic but a strong in-plane anisotropy develops as the coverage is increased to a complete cluster monolayer. At low temperature, thick cluster films have an asperomagnetic configuration that develops into a two-dimensional correlated super spin glass with increasing temperature.

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“…The observed magnetic behavior of the samples at high magnetic fields is not fully clarified yet but the appearance of the paramagnetic-like behaviour can be explained by the occurrence of orbital magnetism due to persistent currents in silicon between the channels of the PS-template. The enhancement of orbital moments is in first principle attributed to the nanoscale nature of the investigated system [9] concerning the incorporated metal nanostructures as well as the nanopatterned template.…”

Section: Methodsmentioning

confidence: 96%

Temperature dependence of a twofold magnetic behaviour of a nanoscopic metal/silicon hybrid system – a comparison between Ni/Si and Co/Si

Rumpf¹,

Granitzer²,

Poelt³

et al. 2009

Phys. Status Solidi (c)

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The investigated hybrid nanocomposite consists of a porous silicon template with electrochemically embedded Ni or Co nanostructures and offers magnetic characteristics which can be tailored by the electrochemical process parameters during fabrication. A twofold magnetic behaviour can be observed, a first one due to the spinmagnetism at magnetic fields below the saturation magnetization of the deposited metals and a second non‐saturating term at higher fields (> 1 T up to 7 T) above the saturation magnetization. In case of Ni deposited within the pores this non‐saturating term shows a paramagnetic characteristic and follows exactly the Curie‐Weiss law, whereas for Co/porous silicon samples the temperature dependent magnetization shows some deviations from the Curie Weiss law. In this high field region a difference in the temperature dependence between Ni and Co is observed whereas the non‐saturating term does not depend on the geometry of the embedded nanostructures in contrast to the ferromagnetic behaviour at lower magnetic fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Highly enhanced orbital magnetism on cobalt cluster surfaces

Cited by 26 publications

References 22 publications

Electrical Characteristics of Controlled-Polarization-Type Ferroelectric-Gate Field-Effect Transistor

Electrical Characteristics of Controlled-Polarization-Type Ferroelectric-Gate Field-Effect Transistor

Magnetism in Fe Nanoclusters ? From Isolated Particles to Nanostructured Materials

Temperature dependence of a twofold magnetic behaviour of a nanoscopic metal/silicon hybrid system – a comparison between Ni/Si and Co/Si

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