Electronic properties of transition-metal clusters:Consideration of the spillover in a bulk parametrization

Guevara, Javier; Parisi, F.; Llois, A.M.; Weissmann, Mariana

doi:10.1103/physrevb.55.13283

Cited by 85 publications

(114 citation statements)

References 34 publications

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“…To account for the electron spillover existing on cluster surfaces, following Weissmann's group 12 , we introduce an extra orbit sЈ to each surface atom iЈ ͑atom with coordination number ZϽ12 for Ni clusters͒, and add the fourth term to our Hamiltonian ͑1͒. We assume this orbit sЈ to locate in the vacuum outside the surface, has an s symmetry, an energy ⑀ s Ј 0 , and interact with s orbit of the same surface atom by hopping integral t ssЈ .…”

Section: Model Hamiltonian and Methodologymentioning

confidence: 99%

“…In another TB calculation, Guevera et al 12 studied the ideally cut fcc Ni clusters. They used a Hamiltonian similar to ours, i.e., adding sЈ orbits to surface atoms to consider the electron spillover.…”

Section: A Size Dependence Of Spin Momentmentioning

confidence: 99%

“…After considering the spillover of electrons, Weissmann and co-workers, 12 introduced an intersite Coulomb term to describe the valence level shift,…”

Section: ͑7͒mentioning

confidence: 99%

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Orbital polarization, surface enhancement and quantum confinement in nanocluster magnetism

et al. 2004

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Within a rather general tight-binding framework, we studied the magnetic properties of Ni n clusters with nϭ9 -60. In addition to usual hopping, exchange, and spin-orbit coupling terms, our Hamiltonian also included orbital correlation and valence orbital shift of surface atoms. We show that orbital moment not only contributes appreciably to the total moment in this range of cluster size, but also dominates the oscillation of total moment with respect to the cluster size. Surface enhancement is found to occur not only for spin but, even stronger, also for orbital moment. The magnitude of this enhancement depends mainly on the coordination deficit of surface atoms, well described by a simple interpolation. For very small clusters (nр20), quantum confinement of 4s electrons has drastic effects on 3d electron occupation, and thus greatly influences both spin and orbital magnetic moments. With physically reasonable parameters to account for orbital correlation and surface valence orbital shift, our results are in good quantitative agreement with available experiments, evidencing the construction of a unified theoretical framework for nanocluster magnetism.

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Section: Model Hamiltonian and Methodologymentioning

confidence: 99%

Section: A Size Dependence Of Spin Momentmentioning

confidence: 99%

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Orbital polarization, surface enhancement and quantum confinement in nanocluster magnetism

et al. 2004

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“…However, they had not optimized the structures and considered only some special structures with lattice parameters same as the bulk Co. Guevara et al 13 used an unrestricted Hartree-Fock (HF) tight-binding formalism, starting from spd-bulk parameterization, but they only considered fixed body-centered cubic (bcc) and fcc geometries for a maximum of 177 atoms without structural relaxation. Andriotis and Menon 14 have used a tightbinding molecular dynamics scheme to study cobalt clusters for some selected cluster sizes.…”

mentioning

confidence: 99%

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Datta¹,

Kabir²,

Ganguly³

et al. 2007

Phys. Rev. B

159

179

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The structural, electronic and magnetic properties of Con clusters (n =2−20) have been investigated using density functional theory within the pseudopotential plane wave method. An unusual hexagonal growth pattern has been observed in the intermediate size range, n =15−20. The cobalt atoms are ferromagnetically ordered and the calculated magnetic moments are found to be higher than that of corresponding hcp bulk value, which are in good agreement with the recent SternGerlach experiments. The average coordination number is found to dominate over the average bond length to determine the effective hybridization and consequently the cluster magnetic moment.

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“…Magnetic properties of transition metal clusters have become the subject of intensive research, both from the experimental [1][2][3][4] and theoretical point of view [5][6][7][8] . One of the most interesting and challenging aspects of that field is the subtle interplay between geometric structure and magnetic ordering which has mostly been investigated for ferromagnetic 3d-clusters and 4d-clusters.…”

Section: Introductionmentioning

confidence: 99%

Noncollinear magnetic ordering in small chromium clusters

Kohl

Bertsch

1999

Phys. Rev. B

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We investigate noncollinear effects in antiferromagnetically coupled clusters using the general, rotationally invariant form of local spin-density theory. The coupling to the electronic degrees of freedom is treated with relativistic non-local pseudopotentials and the ionic structure is optimized by Monte-Carlo techniques. We find that small chromium clusters (N ≤ 13) strongly favor noncollinear configurations of their local magnetic moments due to frustration. This effect is associated with a significantly lower total magnetization of the noncollinear ground states, ameliorating the disagreement between Stern-Gerlach measurements and previous collinear calculations for Cr12 and Cr13. Our results further suggest that the trend to noncollinear configurations might be a feature common to most antiferromagnetic clusters.

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Electronic properties of transition-metal clusters:Consideration of the spillover in a bulk parametrization

Cited by 85 publications

References 34 publications

Orbital polarization, surface enhancement and quantum confinement in nanocluster magnetism

Orbital polarization, surface enhancement and quantum confinement in nanocluster magnetism

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

Noncollinear magnetic ordering in small chromium clusters

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