Search results for "circular"
showing 10 items of 856 documents
Element-specific magnetic moments from core-absorption magnetic circular dichroism of the doped Heusler alloyCo2Cr0.6Fe0.4Al
2003
The magnetic circular dichroism (MCD) of core-level absorption (x-ray absorption spectroscopy, XAS) spectra in the soft x-ray region has been measured for the ferromagnetic Heusler alloy ${\mathrm{Co}}_{2}{\mathrm{Cr}}_{0.6}{\mathrm{Fe}}_{0.4}\mathrm{Al}$ at the Co, Fe, and Cr ${L}_{II,III}$ edges. The comparison of XAS spectra before and after in situ cleaning of polished surfaces revealed a pronounced selective oxidation of Cr in air. For clean surfaces we observed a MCD for all three elements with Fe showing the largest moment per atom. The MCD can be explained by the density of states of the $3d$ unoccupied states, predicted by linear muffin-tin orbital atomic sphere approximation. For …
New Materials with High Spin Polarization Investigated by X-Ray Magnetic Circular Dichroism
2013
We investigate element-specific spin and orbital magnetic moments of polycrystalline bulk Heusler alloys that are predicted to be half-metallic with composition Co2YZ (Y = Ti, Cr, Mn, Fe and Z = Al, Ga, Si, Ge, Sn, Sb) using magnetic circular dichroism in X-ray absorption spectroscopy (XAS/XMCD). In addition to stoichiometric compounds we also investigate composition series with partly replaced elements on the Y-site (Co2Fe x Cr1−x Si, Co2Mn x Ti1−x Si and Co2Mn x Ti1−x Ge) and on the Z-site (Co2MnGa1−x Ge x ) promising a tailoring of the Fermi level with respect to the minority band gap. We compare experimental results with theoretical predictions elucidating the influence of local disorde…
Persistent currents in a circular array of Bose-Einstein condensates
2002
A ring-shaped array of Bose-Einstein condensed atomic gases can display circular currents if the relative phase of neighboring condensates becomes locked to certain values. It is shown that, irrespective of the mechanism responsible for generating these states, only a restricted set of currents are stable, depending on the number of condensates, on the interaction and tunneling energies, and on the total number of particles. Different instabilities due to quasiparticle excitations are characterized and possible experimental setups for testing the stability prediction are also discussed.
Valence band photoemission from thin iron films - A comparison of experimental and theoretical results
1998
Abstract In this contribution, we report on photoemission data from thin iron films on W(110) that have been carried out by means of spin-resolved photoelectron spectroscopy as well as Magnetic Circular Dichroism in valence band photoemission at the storage ring BESSY. These techniques give complementary information on the electronic and magnetic properties, such as exchange and spin–orbit splitting. We compare our experimental data to new photoemission calculations, which have been obtained in the framework of a fully relativistic one-step theory for ferromagnetic materials.
Investigation of a novel material for magnetoelectronics: Co2Cr0.6Fe0.4Al
2003
Heusler compounds are promising candidates for future spintronics device applications. The electronic and magnetic properties of Co2Cr0.6Fe0.4Al, an electron-doped derivative of Co2CrAl, are investigated using circularly polarized synchrotron radiation and photoemission electron microscopy (PEEM). Element specific imaging reveals needle shaped Cr rich phases in a homogeneous bulk of the Heusler compound. The ferromagnetic domain structure is investigated on an element-resolved basis using x-ray magnetic circular dichroism (XMCD) contrast in PEEM. The structure is characterized by micrometre-size domains with a superimposed fine ripple structure; the lateral resolution in these images is abo…
A new BEDT-TTF salt and polypyrrole films containing the chiral polyoxometalate [H4Co2Mo10O38]6−
2005
Abstract The chiral polyoxometalate [H4Co2Mo10O38]6− has been used in the preparation of hybrid materials in the form of crystals or polymeric films. A new radical salt of the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) containing the two enantiomers of this polyoxometalate has been obtained by electrocrystallization. This radical salt shows semiconducting behavior with room temperature conductivity of 9 S.cm−1 and activation energy of 40 meV. Polypyrrole films doped with a racemic mixture of polyoxometalates and also the enantiomerically pure (+)589-[H4Co2Mo10O38]6− have been prepared electrochemically. Circular dichroism experiments suggest that the chiral polyoxometalate…
Alkali-activated mortars for sustainable construction material: effects of binder-to-aggregate ratio and curing conditions
2019
Valorisation and reuse of industrial wastes has become a worldwide compelling topic to improve the sustainability of processes and materials. This paper discusses an alternative way to recycle the biomass fly ash, generated by the kraft pulp industry, to manufacture novel geopolymeric mortars intended for applications in construction. Biomass fly ash was used as a raw material, in partial substitution of the commonly used metakaolin, natural siliceous sand as aggregate. The followed manufacture process is highly simple and reproducible. Various proportions binder to aggregate were tested to study the effect on the final mortars properties. The mortars mechanical resistance was also studied …
ALKALI-ACTIVATED MORTARS FOR SUSTAINABLE CONSTRUCTION MATERIAL: EFFECTS OF BINDER-TO- AGGREGATE RATIO AND CURING CONDITION
2019
Valorisation and reuse of industrial wastes has become a worldwide compelling topic to improve the sustainability of processes and materials. This paper discusses an alternative way to recycle the biomass fly ash, generated by the kraft pulp industry, to manufacture novel geopolymeric mortars intended for applications in construction. Biomass fly ash was used as a raw material, in partial substitution of the commonly used metakaolin, natural siliceous sand as aggregate. The followed manufacture process is highly simple and reproducible. Various proportions binder to aggregate were tested to study the effect on the final mortars properties. The mortars mechanical resistance was also studied …
Plastic or not plastic? That’s the problem: analysing the Italian students purchasing behavior of mineral water bottles made with eco-friendly packag…
2022
Abstract European Strategy for Plastics in a Circular Economy draws new shapes of economy in order to protect the environment and reduce marine pollution, GHGs and countries’ dependence on imported fossil fuels. The core of EU Strategy is also to try to transform the way plastic products are designed, produced, used and recycled in the EU. Italy is the first country in Europe and the second in the world for consumption of bottled water, with remarkable environmental impacts, from production to distribution. Starting from social science theory, this work aims to investigate consumers' behavior and the related factors that influence their behavior pertaining to the purchase of. mineral water …
Optimal Starting Conditions for the Rendezvous Maneuver, Part 1: Optimal Control Approach
2008
We consider the three-dimensional rendezvous between two spacecraft: a target spacecraft on a circular orbit around the Earth and a chaser spacecraft initially on some elliptical orbit yet to be determined. The chaser spacecraft has variable mass, limited thrust, and its trajectory is governed by three controls, one determining the thrust magnitude and two determining the thrust direction. We seek the time history of the controls in such a way that the propellant mass required to execute the rendezvous maneuver is minimized. Two cases are considered: (i) time-to-rendezvous free and (ii) time-to-rendezvous given, respectively equivalent to (i) free angular travel and (ii) fixed angular trave…