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Magnetism of free and supported clusters: a comparative study

100%
Šipr O. e., Minár J. n., Ebert H.
Open Physics
|
2009
|
vol. 7
|
issue 2
257-263
EN
The presented work investigates the differences in magnetic properties of free and supported clusters via ab-initio calculations. The electronic structure of the clusters was calculated using a spin polarized relativistic multiple-scattering Green’s function formalism. We focus on Fe clusters of 2–9 atoms, either free or supported by Ni(001), and on Co clusters of 2–7 atoms, either free or supported by Au(111). For the supported clusters, the spin and orbital magnetic moments depend on the cluster size nearly monotonically, while for the free clusters large quasi-oscillations of magnetic moments with the cluster size were observed. Similarly, for supported clusters, the local spin magnetic moments decrease nearly linearly with increasing coordination number, while for free clusters of the same size range the trend is much more complicated. These findings are consistent with the fact that the spectral distribution function contains much sharper features for free clusters than for supported clusters.
2
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Magnetic cluster developement in In1−x MnxSb semiconductor alloys

88%
Rednic L., Deac I., Dorolti E., Coldea M., Rednic V., Neumann M.
Open Physics
|
2010
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vol. 8
|
issue 4
620-627
EN
X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and magnetic measurements as a function of applied magnetic field and temperature for In1−x MnxSb (0.05≤x≤0.2) system are reported. Magnetic measurements performed at high and small magnetic field in ZFC and FC indicate the coexistence of ferromagnetic In1−x MnxSb solid solution and two types of magnetic cluster: ferromagnetic MnSb and ferrimagnetic Mn2Sb. XPS valence band and Mn 2p core level spectra have confirmed the presence of MnSb and Mn2Sb phases. TEM images show some manganese antimonide phase microinclusions with dimension between (30–40) nm.
3
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Organization of matter into one-dimensional units on designed media

88%
Paul K.
Open Physics
|
2011
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vol. 9
|
issue 2
360-368
EN
The organization of magnetic materials into one-dimensional micro- and nanowires on designed media is discussed, exemplified by two experiments on the microscale and nanoscale, with regard to particles as basic building blocks for the growth and development of matter. In the first organizational experiments, cobalt (Co) micro-particles are assembled on patterned media with perpendicular magnetization by acoustic vibrations onto designed shapes reflecting macroscopically the parent material. In the second experiments, semiconductor Germanium-Dysprosium (Ge98Dy2) matter is assembled on gold (Au) catalytic nuclei in a tube reactor by physical vapor transport as clusters of nanowires. The underlying mechanisms of organization are described, and similarities and distinctive features in the processes are discussed. The role of the energy-input in the form of mechanical vibrations and heat is outlined with its similar impact on the assembly and growth of matter on surfaces. The description of these experiments in view of organization allows more control over the processes of planned arrangement on designed media. Routes for further progress in this direction are briefly outlined.
4
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Determinanty i bariery w procesie zmiany ścieżki rozwoju niemieckiego regionu Brandenburgii

75%
Dąbrowska A.
Studia KPZK
|
2017
|
issue 179
5
Content available remote

Classical simulations of magnetic structures for chromium clusters: Size effects

75%
Proykova A., Stauffer D.
Open Physics
|
2005
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vol. 3
|
issue 2
209-220
EN
Classical (Heisenberg) simulations show that the total magnetization of the lowest-energy states of clusters made of antiferromagnetically coupled chromium atoms is planar, rather than collinear, depending on the arrangement of the atoms. Although the model Hamiltonian is not restrictive, many cluster configurations of various numbers of atoms do not use all three directions for the spins. This result confirms the conclusion drawn from the local-spin DFT calculation by Kohl and Bertsch that clusters of N≤13 have non-collinear magnetic moments. The present simulations show non-collinear spin ordering also for bigger clusters, designed to be as spherical as possible following the bcc arrangement, when atoms interact both with the nearest and next-nearest neighbours. Depending on the signs of the coupling constants frustration appears. The advantage of the discrete model, despite the simplicity, is that very large clusters and magnetization at finite temperatures can be studied. This model predicts that clusters with specific numbers of atoms interacting only with the nearest neighbours have collinear spins as in the bulk. We also apply the model to simulate the destruction of the anti-ferromagnetic ordering by thermal fluctuations. This model shows no unique magnetization of mixed Fe 0.33 Cr 0.67, which is consistent with experimental observations.
6
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Clusterization of water molecules as deduced from statistical mechanical approach

75%
Krasnoholovets V.
Open Physics
|
2004
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vol. 2
|
issue 4
698-708
EN
Using the methods of statistical mechanics we have shown that a homogeneous water network is unstable and spontaneously disintegrates to the nonhomogeneous state (i.e. peculiar clusters), which can be treated as an ordinary state of liquid water. The major peculiarity of the concept is that it separates the paired potential into two independent components-the attractive potential and the repulsive one, which in turn should feature a very different dependence on the distance from the particle (a water molecule in the present case). We choose the interaction potential as a combination of the ionic crystal potential and the vibratory potential associated with the elastic properties of the water system as a whole. The number ℵ of water molecules that enters a cluster is calculated as a function of several parameters, such as the dielectric constant, the mass of a water molecule, the distance between nearest molecules, and the vibrations of nearest molecules in their nodes. The number of H2O molecules that comprise a cluster is estimated as about ℵ ≈ 900, which agrees with the available experimental data.
7
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Сluster and Cluster Initiatives of Rural Tourism in Ukraine

75%
Malska M., Dubis L., Zinko Y.
Biuletyn KPZK
|
2018
|
issue 269
8
Content available remote

A thermodynamic approach to mechanical stability of nanosized particles

51%
Samsonov V., Sdobnyakov N.
Open Physics
|
2003
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vol. 1
|
issue 2
344-354
EN
Thermodynamic stability conditions for nanoparticles (resulting from non-negativity of the second variation of the free energy) have been analyzed for two cases: (i) a nonvolatile nanosized particle with the size-dependent surface tension; (ii) the limiting case of larger objects when the surface tension takes its macroscopic value. It has been shown that the mechanical stability of a nanoparticle, i.e. its stability relative to the volume fluctuations, is defined by an interplay between the excess (“surface”) free energy and the volumetric elastic energy. According to the results obtained, noble gas clusters and metal nanoparticles satisfy the mechanical stability condition. At the same time, water nanodrops, as well as nanoparticles presented by nonpolar organic molecules, correspond to the stability limit. Among the investigated systems, the stability condition is not carried out for n-Pentane clusters.
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