Orbital polarization, surface enhancement and quantum confinement in nanocluster magnetism

Wan, Xiangang; Zhou, Lei; Dong, Jianji; Lee, Ting-Kuo; Wang, Dingsheng

doi:10.1103/physrevb.69.174414

Cited by 33 publications

(28 citation statements)

References 34 publications

(93 reference statements)

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“…However, the error bars are quite large and a monotonic dependence is still consistent with the data [4]. In contrast to supported clusters, magnetic moments of free clusters exhibit a non-monotonic dependence on the cluster size within a small as well as an extended range of sizes [35,48,49]. It is thus possible that the substrate suppresses the tendency of magnetic moments to oscillate when the cluster size is varied.…”

Section: Size Dependence Of Average Magnetic Momentssupporting

confidence: 71%

Magnetic moments, exchange coupling, and crossover temperatures of Co clusters on Pt(111) and Au(111)

Šipr

Bornemann

Minář

et al. 2007

J. Phys.: Condens. Matter

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The influence of cluster size and of cluster-substrate interaction on the magnetic properties of Co clusters of 1-10 atoms on Pt(111) and Au(111) is studied by fully relativistic ab initio calculations. The focus is on systematic trends of the spin and orbital magnetic moments, the exchange coupling, and the crossover temperature. The spin magnetic moments of Co clusters are larger for the Pt substrate than for the Au substrate, while the reverse is true for the orbital magnetic moments. The local magnetic moments of Co atoms generally increase if the number of Co neighbours decreases. The exchange coupling constants J i j depend on the cluster size and on the location of respective atoms. The crossover temperature increases monotonically with cluster size and is larger for clusters on Pt than for clusters on Au.

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Section: Size Dependence Of Average Magnetic Momentssupporting

confidence: 71%

Magnetic moments, exchange coupling, and crossover temperatures of Co clusters on Pt(111) and Au(111)

Šipr

Bornemann

Minář

et al. 2007

J. Phys.: Condens. Matter

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“…The spin magnetic moments µ spin of Ni clusters calculated by Wan et al [54] are in reasonable agreement with density functional calculations [45,47,55], but both approaches, that is, TB and DFT, give smaller values than the experimental magnetic moments. It can be noticed in Fig.…”

Section: Orbital Polarizationsupporting

confidence: 67%

“…The analysis of Wan et al indicates that the magnetic moments of the Ni clusters are dominated by the contribution of surface atoms [53,54]. The orbital and spin local moments of atoms with coordination 8 or larger are similar to those in the bulk (µ bulk,spin ≈ 0.55µ B ; µ bulk,orb ≈ 0.05µ B ) [56]; that is, the orbital moment is almost quenched for internal cluster atoms.…”

Section: Orbital Polarizationmentioning

confidence: 97%

“…Guirado-López et al [53] and of Wan et al [54] have pointed out the relevance of the orbital contribution to the magnetic moment of nickel clusters. The work of Andriotis and Menon [57], formulated also in the TB framework, supports the idea of enhanced orbital moments in Ni clusters, but raises the possibility that the states in which orbital moments are aligned parallel to the spin moments are energetically unfavorable.…”

Section: Orbital Polarizationmentioning

confidence: 99%

“…However, it is known that orbital correlation has a strong effect in low dimensional systems, leading to orbital-polarized ground states [51][52][53]. Guirado-López et al [53] and Wan and coworkers [54] have studied the magnetic moments of Ni clusters taking into account both spin and orbital effects. The Hamiltonian employed by Wan and coworkers is an extension of the tight-binding Hamiltonian of Eq.…”

Section: Orbital Polarizationmentioning

confidence: 99%

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Magnetism

2011

Structure and Properties of Atomic Nanoclusters

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Structure and Properties of Atomic Nanoclusters Downloaded from www.worldscientific.com by KAINAN UNIVERSITY on 03/11/15. For personal use only.Magnetism 319 subshells are separated by the exchange interaction. These atoms have nonzero spins, and since the spin magnetic moment of an electron is 1 Bohr magneton (µ B ), the atoms have substantial moments. When the atoms come together in a cluster or in a metal, the overlap between the atomic orbitals of neighbor atoms gives rise to energy bands. The levels corresponding to 4s electrons produce a free electron-like band with a width in the solid of W = 20-30 eV, while the d electrons stay localized on the atomic sites, and the d band width is much smaller, typically 5-10 eV in the bulk. The crystal potential stabilizes the d and s states by different amounts. This, plus spd hybridization, leads to charge transfer from s to d states, and the number of s electrons for systems other than the atom is close to 1. Assuming that the 3d orbitals are atomic-like, Hund's rule requires the majority 3d ↑ sub-band to be fully occupied with five electrons per atom while the minority 3d ↓ sub-band has two, three, and four electrons per atom in Fe, Co and Ni, respectively. The difference in the number of spin ↑ and spin ↓ 3d electrons per atom is n d ( ↑ ) -n d ( ↓ ) = 3, 2, 1 for Fe, Co, and Ni, respectively, and the magnetic moments per atom are µ (Fe) = 3 µ B , µ (Co) = 2 µ B , µ (Ni) = 1µ B . These values are quite close to the magnetic moments of very small clusters. The bulk moments, µ (Fe) = 2.2 µ B , µ (Co) = 1.7 µ B , µ (Ni) = 0.64µ B , are smaller, and their noninteger values originate in the partial delocalization of the 3d electrons, which also contributes to the mutual alignment of the moments. This is known as itinerant exchange. The onset of delocalization of the d electrons has been studied by comparing the photoelectron spectra of Ni N − and Pd N − to those of Cu N − [11,12]. In small Cu clusters the orbitals of the 3d 10 shell are well localized, and bonding is due mainly to the 4s electrons. The photoelectron spectra of Ni N − clusters with N ≤ 6 are similar to the spectra for Cu N − . The reason is that the 3d orbitals of Ni clusters (N < 7)are well localized and the interaction between the 3d 9 cores of different atoms is negligible. The spectra of larger clusters reflects the delocalization of the 3d electrons. Data for small Pd N − clusters presents some similarities to Ni N − . Structure and Properties of Atomic Nanoclusters Downloaded from www.worldscientific.com by KAINAN UNIVERSITY on 03/11/15. For personal use only. Structure and Properties of Atomic Nanoclusters Downloaded from www.worldscientific.com by KAINAN UNIVERSITY on 03/11/15. For personal use only.

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Magnetic Properties of Atomic Clusters of the Transition Elements

Alonso

2007

Reviews in Computational Chemistry

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Orbital polarization, surface enhancement and quantum confinement in nanocluster magnetism

Cited by 33 publications

References 34 publications

Magnetic moments, exchange coupling, and crossover temperatures of Co clusters on Pt(111) and Au(111)

Magnetic moments, exchange coupling, and crossover temperatures of Co clusters on Pt(111) and Au(111)

Magnetism

Magnetic Properties of Atomic Clusters of the Transition Elements

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