312 research outputs found
d0 Ferromagnetic Interface Between Non-magnetic Perovskites
We use computational and experimental methods to study d0 ferromagnetism at a
charge- imbalanced interface between two perovskites. In SrTiO3/KTaO3
superlattice calculations, the charge imbalance introduces holes in the SrTiO3
layer, inducing a d0 ferromagnetic half-metallic 2D electron gas at the
interface oxygen 2p orbitals. The charge imbalance overrides doping by
vacancies at realistic concentrations. Varying the constituent materials shows
ferromagnetism to be a gen- eral property of hole-type d0 perovskite
interfaces. Atomically sharp epitaxial d0 SrTiO3/KTaO3, SrTiO3 /KNbO3 and
SrTiO3 /NaNbO3 interfaces are found to exhibit ferromagnetic hysteresis at room
temperature. We suggest the behavior is due to high density of states and
exchange coupling at the oxygen t1g band in comparison with the more studied d
band t2g symmetry electron gas.Comment: 5 pages, 5 figure
Effects of deposition dynamics on epitaxial growth
The dynamic effects, such as the steering and the screening effects during
deposition, on an epitaxial growth (Cu/Cu(001)), is studied by kinetic Monte
Carlo simulation that incorporates molecular dynamic simulation to rigorously
take the interaction of the deposited atom with the substrate atoms into
account.
We find three characteristic features of the surface morphology developed by
grazing angle deposition:
(1) enhanced surface roughness, (2) asymmetric mound, and (3) asymmetric
slopes of mound sides.
Regarding their dependence on both deposition angle and substrate
temperature, a reasonable agreement of the simulated results with the previous
experimental ones is found.
The characteristic growth features by grazing angle deposition are mainly
caused by the inhomogeneous deposition flux due to the steering and screening
effects, where the steering effects play the major role rather than the
screening effects.
Newly observed in the present simulation is that the side of mound in each
direction is composed of various facets instead of all being in one selected
mound angle even if the slope selection is attained, and that the slope
selection does not necessarily mean the facet selection.Comment: 9 pages, 10 figure
Characterization of aluminum oxide tunnel barriers by combining transport measurements and transmission electron microscopy imaging
We present two approaches for studying the uniformity of a tunnel barrier. The first approach is based on measuring single-electron and two-electron tunneling in a hybrid single-electron transistor. Our measurements indicate that the effective area of a conduction channel is about one order of magnitude larger than predicted by theoretical calculations. With the second method, transmission electron microscopy, we demonstrate that variations in the barrier thickness are a plausible explanation for the larger effective area and an enhancement of higher order tunneling processes.Peer reviewe
Opportunities and challenges for spintronics
This is the author accepted manuscript. The final version is available from EDP Sciences via the DOI in this recordConventional electronics use the flow of electric charges and are based on standard semiconductors. Spintronic devices exploit the electrons- spin to generate and control currents and to combine electric and magnetic signals. Today there is a strong effort worldwide to integrate spintronic devices with standard CMOS technology towards hybrid spin-CMOS chips, offering advantages in terms of power consumption, compactness, and speed. Recent results (from SAMSUNG [1], TSMC [2], etc.) confirm the merit of this approach
Quasiparticle dynamics in ferromagnetic compounds of the Co-Fe and Ni-Fe systems
We report a theoretical study of the quasiparticle lifetime and the
quasiparticle mean free path caused by inelastic electron-electron scattering
in ferromagnetic compounds of the Co-Fe and Ni-Fe systems. The study is based
on spin-polarized calculations, which are performed within the
approximation for equiatomic and Co- and Ni-rich compounds, as well as for
their constituents. We mainly focus on the spin asymmetry of the quasiparticle
properties, which leads to the spin-filtering effect experimentally observed in
spin-dependent transport of hot electrons and holes in the systems under study.
By comparing with available experimental data on the attenuation length, we
estimate the contribution of the inelastic mean free path to the latter.Comment: 10 pages, 10 figure
Vicinal Surfaces, Fractional Statistics and Universality
We propose that the phases of all vicinal surfaces can be characterized by
four fixed lines, in the renormalization group sense, in a three-dimensional
space of coupling constants. The observed configurations of several Si surfaces
are consistent with this picture. One of these fixed lines also describes
one-dimensional quantum particles with fractional exclusion statistics. The
featureless steps of a vicinal surface can therefore be thought of as a
realization of fractional-statistics particles, possibly with additional
short-range interactions.Comment: 6 pages, revtex, 3 eps figures. To appear in Physical Review Letters.
Reference list properly arranged. Caption of Fig. 1 slightly reworded. Fig 3
(in color) is not part of the paper. It complements Fig.
Cardiovascular health after menopause transition, pregnancy disorders, and other gynaecologic conditions: a consensus document from European cardiologists, gynaecologists, and endocrinologists.
Women undergo important changes in sex hormones throughout their lifetime that can impact cardiovascular disease risk. Whereas the traditional cardiovascular risk factors dominate in older age, there are several female-specific risk factors and inflammatory risk variables that influence a woman's risk at younger and middle age. Hypertensive pregnancy disorders and gestational diabetes are associated with a higher risk in younger women. Menopause transition has an additional adverse effect to ageing that may demand specific attention to ensure optimal cardiovascular risk profile and quality of life. In this position paper, we provide an update of gynaecological and obstetric conditions that interact with cardiovascular risk in women. Practice points for clinical use are given according to the latest standards from various related disciplines (Figure 1)
Parallel evolution of the make–accumulate–consume strategy in Saccharomyces and Dekkera yeasts
Saccharomyces yeasts degrade sugars to two-carbon components, in particular ethanol, even in the presence of excess oxygen. This characteristic is called the Crabtree effect and is the background for the 'make–accumulate–consume' life strategy, which in natural habitats helps Saccharomyces yeasts to out-compete other microorganisms. A global promoter rewiring in the Saccharomyces cerevisiae lineage, which occurred around 100 mya, was one of the main molecular events providing the background for evolution of this strategy. Here we show that the Dekkera bruxellensis lineage, which separated from the Saccharomyces yeasts more than 200 mya, also efficiently makes, accumulates and consumes ethanol and acetic acid. Analysis of promoter sequences indicates that both lineages independently underwent a massive loss of a specific cis-regulatory element from dozens of genes associated with respiration, and we show that also in D. bruxellensis this promoter rewiring contributes to the observed Crabtree effect
- …