Ethological Remarks on Mannerisms

Brüne, Martin

doi:10.1159/000029039

Cited by 161 publications

(305 citation statements)

References 18 publications

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“…The harmonic approximation should only be expected to work well at sufficiently low temperatures, where all modes can be considered harmonic (excluding possible quantum effects at very low temperatures), but several studies have shown that it is often applicable even at rather high temperatures 19,20 and in highly complex systems. 21 The quantum nature of the hydrogen atoms must also be considered.…”

Section: A Transition State Theorymentioning

confidence: 99%

Locating the rate-limiting step for the interaction of hydrogen withMg(0001)using density-functional theory calculations and rate theory

2004

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The dissociation of molecular hydrogen on a Mg͑0001͒ surface and the subsequent diffusion of atomic hydrogen into the magnesium substrate is investigated using Density Functional Theory (DFT) calculations and rate theory. The minimum energy path and corresponding transition states are located using the nudged elastic band method, and rates of the activated processes are calculated within the harmonic approximation to transition state rate theory, using both classical and quantum partition functions based atomic vibrational frequencies calculated by DFT. The dissociation/recombination of H 2 is found to be rate-limiting for the ab-and desorption of hydrogen, respectively. Zero-point energy contributions are found to be substantial for the diffusion of atomic hydrogen, but classical rates are still found to be within an order of magnitude at room temperature.

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Section: A Transition State Theorymentioning

confidence: 99%

Locating the rate-limiting step for the interaction of hydrogen withMg(0001)using density-functional theory calculations and rate theory

2004

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“…To construct such small particles we have exploited the epitaxial growth of Co on Pt(111) in ultra-high-vacuum (UHV), which allows us to obtain a narrow size distribution by means of kinetically controlled growth [23]. This technique exploits the energetic hierarchy of the different diffusion and dissociation processes of adatoms at surfaces, and their dependence on the substrate symmetry.…”

Section: Orbital Magnetic Moment and Magnetic Anisotropy Of Single Comentioning

confidence: 99%

“…This technique exploits the energetic hierarchy of the different diffusion and dissociation processes of adatoms at surfaces, and their dependence on the substrate symmetry. Control is achieved by means of external parameters such as, e.g., the substrate temperature and deposition flux, allowing atoms to diffuse and nucleate forming aggregates of defined size and shape [23]. The Co/Pt system was chosen in order to maximize the MAE effects, since hcp-Co presents the largest MAE among 3d ferromagnetic elements (0.045 meV/atom compared to, e.g., 0.005 meV/atom for Fe).…”

Section: Orbital Magnetic Moment and Magnetic Anisotropy Of Single Comentioning

confidence: 99%

“…Surface-supported nanoparticles offer additional degrees of freedom to tune the magnetic anisotropy by ad-hoc modifications of the particle size, shape, and coupling with the substrate, making nanometer sized systems attractive for basic investigations as well as for miniaturized data storage applications [20][21][22]. In this respect, self-assembled magnetic clusters grown on metal surfaces constitute an ideal system since their size, shape, and composition can be controlled with relative ease while producing them in numbers large enough for investigation with spatially integrating techniques [23,24]. In the following we present an extensive study of the evolution of the magnetic anisotropy energy in surface supported aggregates when their sizes evolve from one to about one thousand atoms.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic anisotropy from single atoms to large monodomain islands of Co/Pt(111)

Gambardella

Rusponi

Cren

et al. 2005

Comptes Rendus. Physique

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By studying the magnetic behavior of self-assembled Co islands on a single-crystal metal surface, Pt(111), we show how the magnetic anisotropy evolves from isolated atoms to monolayer islands and films. Single Co adatoms are found to have a giant magnetocrystalline anisotropy energy of E a = 9.3 ± 1.6 meV/atom arising from the combination of partly preserved orbital moments (m L = 1.1 µ B ) and strong spin-orbit coupling induced by the Pt substrate. Combined scanning tunneling microscopy and X-ray magnetic circular dichroism experiments performed for differently sized small two-dimensional Co islands establish a clear connection between E a and m L , both quantities decrease sharply with the lateral coordination of the magnetic atoms. In accordance with this, Kerr magnetometry experiments, again performed in conjunction with scanning tunneling microscopy, reveal that the anisotropy energy of large two-dimensional Co islands is almost entirely determined by the relatively low number of perimeter atoms, having E a = 0.9 ± 0.1 meV/atom. These results confirm theoretical predictions and are of fundamental value the understanding of how the magnetic anisotropy develops in finite-size magnetic particles. Identification of the role of perimeter and surface atoms opens up new opportunities for engineering the anisotropy and the moment of a magnetic nanostructure. RésuméAnisotropie magnétique de l'atome isolé aux îlots monocouches de Co/Pt(111). En étudiant les propriétés magnétiques de particules de Co auto assemblées sur une surface d'orientation (111) d'un monocristal de Pt, nous montrons comment l'anisotropie magnétique évolue de l'atome isolé aux îlots monocouches et aux films ultraminces. Nous trouvons que les atomes de Co isolés adsorbés en surface ont une énergie d'anisotropie magnétocrystalline de E a = 9.3 ± 1.6 meV/atome provenant de la combinaison d'un moment orbital conservé (m L = 1.1 µ B ) et d'un fort couplage spin-orbite induit par le substrat de Pt. Des expériences combinées de microscopie à effet tunnel et de dichroïsme circulaire magnétique à rayons X, effectués sur des îlots de Co de petit taille établissent une connexion claire entre E a et m L , chacune de ces quantités décroissant rapidement avec la coordination latérale des atomes magnétiques. En conformité avec ceci, nous trouvons en employant la magnétométrie par effet Kerr et le microscope à effet tunnel que l'énergie d'anisotropie de grands îlots bidimensionnels de Co est presque entiè-rement déterminée par le nombre relativement faible d'atomes au périmètre, ayant E a = 0.9 ± 0.1 meV/atome. Ces résultats confirment les prédictions théoriques et sont d'un intérêt fondamental pour comprendre comment l'anisotropie magnétique se développe dans les particules magnétiques de taille finie. L'identification du rôle des atomes au périmètre et des atomes de surface ouvre de nouvelles opportunités pour l'ingénierie de l'anisotropie et du moment de nanostructures magnétiques. Pour citer cet article : P. Gambardella et al., C. R. Physique 6 (200...

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“…Strain-relief patterns formed by heteroepitaxial films act as templates for the self-assembly of highly ordered nanostructure superlattices. 1 The first system where the growth kinetics has been studied is a superlattice of Ag islands grown on a trigonal network (TN) formed by two monolayers (ML) of Ag/Pt(111). 2,3 The system has been modeled by assuming a network of surface Shockley partial dislocations 4 acting as repulsive line defects and thus confining the deposited Ag adatoms into the (25 × 25) unit cells.…”

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confidence: 99%

Interface-confined mixing and buried partial dislocations for Ag bilayer on Pt(111)

et al. 2012

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The trigonal strain-relief pattern formed by an Ag bilayer on Pt(111) is a prominent example for dislocation networks and their use as nanotemplates. However, its atomic structure has not been solved. Combining scanning tunneling microscopy, low-energy ion scattering, and x-ray photoelectron diffraction, we demonstrate that, unexpectedly, about 22% of the atoms exchange across the Ag/Pt interface, and that the partial dislocations defining the trigonal network are buried in the Pt interface layer. We present an embedded-atom-method simulation identifying the lowest energy structure compatible with all experimental findings. Strain-relief patterns formed by heteroepitaxial films act as templates for the self-assembly of highly ordered nanostructure superlattices. 1 The first system where the growth kinetics has been studied is a superlattice of Ag islands grown on a trigonal network (TN) formed by two monolayers (ML) of Ag/Pt(111). 2,3 The system has been modeled by assuming a network of surface Shockley partial dislocations 4 acting as repulsive line defects and thus confining the deposited Ag adatoms into the (25 × 25) unit cells. 2,3 However, the topmost Ag layer of the TN has recently been shown to be nearly perfectly hexagonal; hence there are no partial dislocations at the surface. 5,6 Nevertheless, the TN exhibits remarkable template functions. Well-ordered sputter holes 5 and adsorbed organic molecules, 6-8 as well as strong spatial variations of the local work function 9 have been reported. A fundamental understanding of any template function evidently requires knowledge of its atomic structure. 10 Despite considerable efforts, a realistic atomistic model has not yet been developed for the 2 ML Ag/Pt(111) TN.Silver on Pt(111) is a system with a particularly rich surface phase diagram. Submonolayers deposited at room temperature (RT) are pseudomorphic for islands smaller than 20 nm, whereas larger islands form surface partial dislocations. 11,12 Counterintuitively, the dislocations disappear at a full monolayer (defined as one Ag atom per Pt substrate atom), where the stress resulting from the misfit is largest. This has been related to the chemical adatom potential and to the presence of an adatom gas. 11 Further growth at RT leads to a striped phase (SP) 4,13 with pairs of partial dislocations. Upon annealing to 800 K the SP transforms into the stable TN structure. 4 Deposition of Ag submonolayers at higher temperature, or their annealing at T > 620 K, leads to a real mixture formed by monolayer Ag clusters embedded into the uppermost atomic substrate layer for a coverage < 0.5 ML and the reverse for 0.5 ML < < 1.0 ML. 14 This mixing has been confirmed by CO titration 15 and He-atom scattering 16 and is confined to the uppermost layer; hence, the name "surface alloy". 17 For 1.0 ML, especially for = 2 ML, Ag and Pt were believed to be phase separated up to the Ag desorption temperature.In this paper we report the surprising observation that the system mixes again for 2 ML Ag in the TN structure. This mi...

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Ethological Remarks on Mannerisms

Cited by 161 publications

References 18 publications

Locating the rate-limiting step for the interaction of hydrogen withMg(0001)using density-functional theory calculations and rate theory

Locating the rate-limiting step for the interaction of hydrogen withMg(0001)using density-functional theory calculations and rate theory

Magnetic anisotropy from single atoms to large monodomain islands of Co/Pt(111)

Interface-confined mixing and buried partial dislocations for Ag bilayer on Pt(111)

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