Search results for "Polarization"

Vertical Beam Polarization at MAMI

2017

For the first time a vertically polarized electron beam has been used for physics experiments at MAMI in the energy range between 180 and 855 MeV. The beam-normal single-spin asymmetry $A_{\mathrm{n}}$, which is a direct probe of higher-order photon exchange beyond the first Born approximation, has been measured in the reaction $^{12}\mathrm C(\vec e,e')^{12}\mathrm C$. Vertical polarization orientation was necessary to measure this asymmetry with the existing experimental setup. In this paper we describe the procedure to orient the electron polarization vector vertically, and the concept of determining both its magnitude and orientation with the available setup. A sophisticated method has …

Polarization-Dependent Disappearance of a Resonance Signal -- Indication for Optical Pumping in a Storage Ring?

2021

We report on laser spectroscopic measurements on Li$^+$ ions in the experimental storage ring ESR at the GSI Helmholtz Centre for Heavy Ion Research. Driving the $2s\,^3\!{S}_1\;(F=\frac{3}{2}) \,\leftrightarrow\,2p\,^3\!P_2\;(F=\frac{5}{2}) \leftrightarrow 2s\,^3\!{S}_1\;(F=\frac{5}{2})$ $\Lambda$-transition in $^7$Li$^+$ with two superimposed laser beams it was found that the use of circularly polarized light leads to a disappearance of the resonance structure in the fluorescence signal. This can be explained by optical pumping into a dark state of polarized ions. We present a detailed theoretical analysis of this process that supports the interpretation of optical pumping and demonstrate…

High-spin polarization of Heusler alloys

2006

Fermi surface of a half-metal compound with cubic Fm–3m symmetry: Heusler alloy or double perovskite.The inset shows the spin resolved density of state for a CCFA Heusler compound. ( This illustration appears on the cover of the print edition. ) This cluster issue of Journal of Physics D: Applied Physics is devoted to magnetic Heusler alloys. This class of materials is currently considered to contain the most attractive half-metallic ferromagnets due to their high Curie temperatures and their structural relation to conventional semiconductors. The first compound to be identified as a half-metallic ferromagnet, by de Groot et al back in 1983, was the half-Heusler alloy NiMnSb. After a period…

Effects of post-growth annealing on structural and compositional properties of the Co2Cr0.6Fe0.4Al surface and its relevance for the surface electron…

2009

In this study we investigate the influence of post-growth annealing on different Co2Cr0.6Fe0.4Al samples. We find strong changes in the geometric surface structure as well as in the element specific concentrations during the annealing process. These irreversible changes go in hand with characteristic changes in the electron spin polarization (ESP) at the surface: as observed in Cinchetti et al (2007 J. Phys. D: Appl. Phys. 40 1544), the iron buffered sample shows the largest spin polarization at the Fermi level. The latter remains positive as a consequence of the reduced density of states for the minority carriers due to the predicted minority gap, which can be clearly seen for all samples …

A spatially resolved investigation of the local, micro-magnetic domain structure of single and polycrystalline Co2FeSi

2007

The Heusler compound Co2FeSi is a promising material for magneto-electronic devices. With a Curie temperature of 1100?K and a saturation magnetization of 6?Bohr magnetons and a high spin polarization at the Fermi edge it fulfils the essential requirements for magnetic sensors or spin valve structures. An essential feature for such devices is the micro-magnetic domain structure. X-ray magnetic circular dichroism?photo emission electron microscopy has been used for a direct observation of the domain structure of single- and polycrystalline samples. The polycrystalline material exhibits a micro-magnetic ripple structure, as it is well known for pure Co and other polycrystalline Heusler compoun…

Off-stoichiometry in Co2FeSi thin films sputtered from stoichiometric targets revealed by nuclear magnetic resonance

2009

Co2FeSi is predicted to be a half-metallic ferromagnet with an extraordinary high magnetic moment and Curie temperature. However, a low tunnel magneto-resistance ratio, a lower spin polarization and a lower magnetic moment were experimentally observed in thin film samples. Consequently, thin Co2FeSi films of different groups were studied using spin-echo nuclear magnetic resonance (NMR). NMR probes the local hyperfine fields of the active atoms, which strongly depend on the local environment. NMR is thus able to reveal the next neighbouring shells of the Co-59 nuclei in the Co2FeSi thin films. As expected, our NMR study shows the main resonance line corresponding to Co-59 nuclei in the L2(1)…

High spin polarization in Co2CrAl–Cr superlattice

2009

The electronic structure, magnetic properties and interface effects in Co2CrAl?Cr superstructures have been investigated by the use of first principle calculations. The results show that at the interface, a large magnetic moment and a high spin polarization can be induced by a strong ferromagnetic exchange interaction at the Cr?Co interface. However, at the CrAl?Cr interface, both the magnetic moment and the spin polarization of the Cr atoms are decreased due to a Cr?Cr antiferromagnetic interaction. It can also be found that the interface effect is only a short range effect. So, high spin polarization in Co2CrAl?Cr superlattice can be obtained. Based on this theoretical analysis, a large g…

The relation between neuronal chloride transporter activities, GABA inhibition, and neuronal activity

2020

Abstract The intracellular chloride concentration [Cl−]i in neurons is regulated by a set of transmembrane transporters, with the Cl−-loader NKCC1 and the Cl−-extruder KCC2 as most relevant members. The expression of these transporters is tightly regulated, with the general trend that KCC2 expression is low in immature neurons, which are thus characterized by a high [Cl−]i. As [Cl−]i is the main factor determining the polarity of GABAergic responses, such a high [Cl−]i is related to depolarizing GABAergic responses. However, depolarizing GABAergic responses are not per se excitatory, but can also contribute to shunting inhibition. The excitatory/inhibitory action of GABAergic responses is m…

Gradual complement protein adsorption and macrophage polarization: inflammation & dental implants

2020

Expanded gentamicin volume of distribution in critically ill adult patients receiving total parenteral nutrition

1995

Aminoglycoside antibiotics distribute into the extracellular fluid compartment and are eliminated by the kidney via glomerular filtration. Malnutrition and total parenteral nutrition influence the fluid and electrolyte status of the patient, and cause organ changes. The purpose of this clinical study was to characterize the kinetic behaviour of gentamicin in the parenterally fed critically ill adult patient. Eighty-six critically ill adult patients treated with gentamicin for severe Gram-negative infections were enrolled in the study (mean +/- SD): age, 60 +/- 14 years; weight, 69.4 +/- 10.2 kg; height, 163 +/- 10 cm; 22 females and 64 males. Four study groups were defined (2 x 2): total pa…