Search results for "Magnetism"
showing 10 items of 1934 documents
On the rigidity of back-to-back top quark pairs in e^+e^- annihilation
1998
We consider the effect of gluon radiation on the energy of top/antitop quarks and on the anticollinearity of top-antitop quark pairs produced in $e^+e^-$ annihilation. Our results are presented in terms of the $E_q$-dependence of the $t\bar tg$ cross section and the dependence on the cosine of the opening angle $\theta_{12}$ between top and antitop for a center of mass energy of $\sqrt{q^2}=500 GeV$. We then go on to determine mean values for the top quark's energy as well as its longitudinal and transverse projections, and for the deviation of $\sin\theta_{12}$ and $\cos\theta_{12}$ from the anticollinearity limits $\sin\theta_{12}=0$ and $\cos\theta_{12}=-1$. For a center of mass energy o…
Kl3Semileptonic Form Factor from (2+1)-Flavor Lattice QCD
2008
We present the first results for the ${K}_{l3}$ form factor from simulations with $2+1$ flavors of dynamical domain wall quarks. Combining our result, namely, ${f}_{+}(0)=0.964(5)$ with the latest experimental results for ${K}_{l3}$ decays leads to $|{V}_{us}|=0.2249(14)$, reducing the uncertaintity in this important parameter. For the $O({p}^{6})$ term in the chiral expansion we obtain $\ensuremath{\Delta}f=\ensuremath{-}0.013(5)$.
Switching nuclearity and Co(II) content through stoichiometry adjustment: {Co(II)6Co(III)3} and {Co(II)Co4(III)} mixed valent complexes and a study o…
2015
We are reporting two new mixed valent Co(ii)/Co(iii) polynuclear complexes, {Co II 6 Co III 3 } and {Co II Co III 4 }, bearing different amount of Co(ii) ions in their cores, through the employment of the multidentate triethanolamine (teaH 3 ) ligand in different stoichiometric ratios. We present a complete picture of the magnetic behaviour of both complexes through a combined usage of the susceptibility, magnetization and X-band EPR data as well as broken-symmetry DFT calculations. Compound 1 shows an atypical spin-only behaviour, probably due to the presence of four and five coordinated Co(ii) sites as well as highly distorted six coordinated Co(ii) ions, promoting a high degree of orbita…
Bistable spin-crossover nanoparticles showing magnetic thermal hysteresis near room temperature
2007
We have demonstrated that the reverse micelle technique can be applied to polymeric spin-crossover systems, such as [Fe(Htrz)2(trz)](BF4), to control the growth of the crystallites. Small nanoparticles of diameters around 10 nm and narrow size distribution were obtained. It is easy to envision that, by modifying the synthetic procedure, the size and critical temperatures of these nanoparticles can be tuned. On one hand, different ratios of solvent, water, and surfactants will lead to different micelle sizes, which will affect the particle size and, maybe, the magnetic properties. On the other hand, the critical temperatures can be lowered towards room temperature by changing the composition…
Free Charge Carriers in Mixed Valency Oxides as Possible Mediators of Magnetoelectric Effect
2009
We show, that in a substance with mixed-valence ions, which can supply free carriers and have electric dipole and spin moments, three types of long-range order (ferromagnetic, ferroelectric and magnetoelectric (ME)) can occur at low temperatures. The origin of the effect is that free charge carriers can mediate the multiferroic behavior via spin – spin (RKKY), dipole-dipole and dipole - spin interactions. We show that there is an optimal carrier concentration, at which the strength of ME interaction is maximal and comparable to that of RKKY interaction. Our analysis shows that disorder and finite conductivity in the above substances does not suppress multiferroic effects.
Chalcogen adsorption and surface magnetism
2000
Abstract Investigations concerning the electronic and magnetic properties of oxygen and sulfur adsorbed on magnetized surfaces were carried out by means of angle and spin resolving photoelectron spectroscopy. Iron(110), a polycrystalline iron alloy, and an amorphous metallic glass (Fe 79 B 16 Si 5 ) served as ferromagnetic substrates. Exchange splittings of the O 2p and S 3p derived levels could be detected, demonstrating a magnetic coupling between the chemisorbate and iron. This observation presents a prerequisite for an induced magnetic moment within the adsorbate overlayer. For sulfur an adsorbate-induced structure only in the minority spin channel near the Fermi level was observed whic…
Surface magnetism studied by photoelectron spectromicroscopy with high spatial and time resolution
2004
Abstract Photoemission electron microscopy (PEEM) is widely used for the study of magnetic surfaces and thin films. Ferromagnetic and antiferromagnetic microstructures are investigated exploiting magnetic circular and linear dichroism in the soft X-ray range using tuneable synchrotron radiation. Local dichroism spectroscopy gives access to magnetic moments of the elements in compounds or multilayer materials. Beyond these achievements, the method bears a high future potential with respect to an increased lateral resolution via aberration correction of the electron optics and a high time resolution in the 100 ps range for the study of dynamic processes. In addition, photoelectron spin polari…
Magnetometry of buried layers—Linear magnetic dichroism and spin detection in angular resolved hard X-ray photoelectron spectroscopy
2012
Abstract The electronic properties of buried magnetic nano-layers were studied using the linear magnetic dichroism in the angular distribution of photoemitted Fe, Co, and Mn 2p electrons from a CoFe–Ir78Mn22 multi-layered sample. The buried layers were probed using hard X-ray photoelectron spectroscopy, HAXPES, at the undulator beamline P09 of the 3rd generation storage ring PETRA III. The results demonstrate that this magnetometry technique can be used as a sensitive element specific probe for magnetic properties suitable for application to buried ferromagnetic and antiferromagnetic magnetic materials and multilayered spintronics devices. Using the same instrument, spin-resolved Fe 2p HAXP…
CAD of complex passive devices composed of arbitrarily shaped waveguides using Nyström and BI-RME methods
2004
In this paper, a novel computer-aided design (CAD) tool of complex passive microwave devices in waveguide technology is proposed. Such a tool is based on a very efficient integral-equation analysis technique that provides a full-wave characterization of discontinuities between arbitrarily shaped waveguides defined by linear, circular, and/or elliptical arcs. For solving the modal analysis of such arbitrary waveguides, a modified version of the well-known boundary integral-resonant-mode expansion (BI-RME) method using the Nyström approach, instead of the traditional Galerkin version of the method of moments, is proposed, thus providing significant savings on computational costs and implement…
RbBr and CsBr doped with Eu2+ as new competitive X-ray storage phosphors
2001
Abstract After X-irradiation of the alkali halides RbBr and CsBr doped with divalent Eu a significant photostimulated luminescence (PSL) effect was found. In both systems the electron trap centre is an F centre, the hole trap centre is still unknown. The Eu 2+ aggregation with cation vacancies plays an important role. Although all of the different Eu 2+ aggregates seem to show PSL effects, they have different PSL efficiencies, decay times and spectral characteristics. In the case of RbBr:Eu 2+ it was possible to investigate the different Eu 2+ -cation vacancy aggregate states by magnetic circular dichroism of the optical absorption (MCDA) and MCDA-detected electron paramagnetic resonance. I…