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Perpendicular Magnetic Anisotropy Induced by Tetragonal Distortion of FeCo Alloy Films Grown on Pd(001)

Physical Review Letters 2006年第25期96卷 257205-257205页

作者： Aimo Winkelmann Marek Przybylski Feng Luo Yisheng Shi Jochen Barthel Max-Planck Institut für Mikrostrukturphysik Weinberg 2 D-06120 Halle (Saale) Germany Solid State Physics Department Faculty of Physics and Applied Computer Science AGH University of Science and Technology Mickiewicza 30 30-059 Krakow Poland

We grew tetragonally distorted FexCo1−x alloy films on Pd(001). Theoretical first-principles calculations for such films predicted a high saturation magnetization and a high uniaxial magnetic anisotropy energy for specific values of the lattice distortion c/a and the alloy composition x. The magnetic anisotropy was investigated using the magneto-optical Kerr effect. An out-of-plane easy axis of magnetization was observed for Fe0.5Co0.5 films in the thickness range of 4 to 14 monolayers. The magnetic anisotropy energy induced by the tetragonal distortion is estimated to be almost 2 orders of magnitude larger than the value for bulk FeCo alloys. Using LEED Kikuchi patterns, a change of the easy axis of magnetization can be related to a decrease of the tetragonal distortion with thickness.

关键词： Iron alloys

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Co-localization of copper, zinc and lead with calcium in their accumulation sites in the housefly's abdomen by micro-PIXE

Co-localization of copper, zinc and lead with calcium in the...

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作者： Tylko, Grzegorz Borowska, Joanna Banach, Zuzanna Pyza, Elzbieta Przybylowicz, Wojciech J. Mesjasz-Przybylowicz, Jolanta Materials Research Group IThemba LABS Somerset West South Africa Department of Cytology and Histology Jagiellonian University Kraków Poland Faculty of Physics and Applied Informatics AGH University of Science and Technology Kraków Poland

Our previous study showed that treatment of Musca domestica larvae with semi-lethal doses of Cu, Zn or Pb leads to their accumulation in the adult fly's abdomen. Now we report that the distribution pattern of heavy metals is similar to that of Ca. The housefly's larvae were reared on media contaminated with semi-lethal doses of Cu (800∈ppm), Zn (2000∈ppm) or Pb (10,000∈ppm) and on control medium. Ten days after eclosion, adult houseflies were prepared for X-ray microanalysis. Analyses were performed on the whole freeze-dried abdomen specimens using a nuclear microprobe (PIXE and RBS) at iThemba LABS, South Africa. GeoPIXE II software was used to obtain quantitative elemental maps by the Dynamic Analysis method. On the basis of Cu, Zn and Pb accumulation sites, the concentrations of these elements were correlated with the concentration of Ca. There was a clear relationship between Ca and all heavy metals examined, indicating Ca co-localization in their deposition sites. In the control animals, Zn and Ca deposition sites were significantly correlated. Association of heavy metals with Ca in their accretion sites suggests the presence of metal-accumulating granules, the so-called "concretions" probably in the Malpighian tubules, midgut epithelium or in the fat body.

关键词： Heavy metals

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Broken one-particle symmetry in few-electron coupled quantum dots

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Physical Review B 2006年第7期73卷 075422-075422页

作者： T. Chwiej S. Bednarek B. Szafran J. Adamowski F. M. Peeters Faculty of Physics and Applied Computer Science AGH University of Science and Technology PL-30059 Kraków Poland Departement Fysica Universiteit Antwerpen (UA/CGB) Groenenborgerlaan 171 B-2020 Antwerpen Belgium

Few-electron systems confined in vertically coupled quantum dots are studied by exact methods and through the local spin density approximation (LSDA). Special attention is paid to the recovering of the one-particle symmetry properties in the LSDA. It is shown that—in spite of accurate energy estimates—the LSDA does not reproduce the one-particle parity and the relative probability of finding a definite number of electrons in the different quantum dots. This symmetry breaking appears for certain electron configurations and intermediate thickness of the interdot barrier and is a direct result of electron-electron correlation. We discuss the effect of correlation on the symmetry properties of the few-electron wave function and determine the limits of the applicability of the LSDA for coupled quantum dots.

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Functionalized carbazole AZO dyes for nonlinear optical application

Functionalized carbazole AZO dyes for nonlinear optical appl...

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8th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2006

作者： Sahraoui, B. Czaplicki, R. Kajzar, F. Nizioll, Jacek Bednarz, Monika Laboratoire POMA UMR CNRS 6136 Universite d'Angers 2 Boulevard Lavoisier 49045 Angers Cedex France Faculty of Physics and Applied Computer Science AGH- University of Science and Technology al. Mickiewicza 30 30-059 Krakow Poland Department of Polymer Science and Technology Cracow University of Technology ul. Warszawska 24 31-155 Krakow Poland

ISBN: (纸本)1424402336

Nonlinear optics has been the subject of intensive research, because of its wide applications in field of photonics, nanophotonics and optoelectronics such as optical signal processing, broadband optical communications, integrated optics, optical sensing, optical poling, optical limiting, optical computing etc. Optical materials, with large coefficients of TPA and nonlinear refraction, are of prime importance in nonlinear optical applications Recently the carbazole azo dyes have attracted much attention because they are forming a spacious group of products which shows a wide range of colours and shades. These compounds are of significant importance for chemistry and technological applications particularly for optoelectronics applications. They are mostly obtained by the coupling reaction of diazonium salts and amines or phenols. We show that such compounds could be suitable candidate and promising materials for nonlinear optical application. In this talk third nonlinear optical properties using DFWM and THG will be discussed. Additionally in this talk illustration of new system for optical recording and erasing of holograms under weak laser illumination will be discussed. © 2006 IEEE.

关键词： Dyes

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DEDIX - Development of Fully Integrated Multichannel ASIC for High Count Rate Digital X-ray Imaging Systems

DEDIX - Development of Fully Integrated Multichannel ASIC fo...

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IEEE Symposium on Nuclear science (NSS/MIC)

作者： P. Grybos P. Maj R. Szczygiel L. Ramello M. Idzik K. Swientek T. Stobiecki Faculty of Electrical Engineering Automatics Computer Science and Electronics Department of Measurement and Instrumentation AGH University of Science and Technology Cracow Poland Dipartimento Scienze e Tecnologie Avanzate Universita del Piemonte Orientale and INFN Alessandria Italy Faculty of Physics and Applied Computer Science AGH University of Science and Technology Cracow Poland Faculty of Electrical Engineering Automatics Computer Science and Electronics Department of Electronics AGH University of Science and Technology Cracow Poland

We present the development of a 64 channel readout ASIC called DEDIX for high count rate position-sensitive measurements using semiconductor detectors. The ASIC is designed in 0.35 mum CMOS process and its total area is 3400 times 5000 mum 2 . The DEDIX has a binary readout architecture. Each channel is built of a charge sensitive amplifier (CSA) with a pole-zero cancellation circuit, a shaper, two independent discriminators and two independent 20-bit counters. The size of the input device in CSA has been optimized for a detector capacitance in the range of 1-3 pF per strip. An equivalent noise charge of 110 el rms has been achieved for a total detector capacitance of 1 pF at the shaper peaking time of 160 ns. Internal correction DAC implemented in each channel independently ensures the low spread of effective threshold of discriminators at 0.4 mV on one sigma level. The mean gain in the multichannel ASIC is 54 muV/el, with a good uniformity from channel to channel (sd/mean = 0.8%). Low noise performance and high rate capability have been demonstrated by the measurement up to and above 1 MHz of average rate of input signals.

关键词： Application specific integrated circuits X-ray imaging Capacitance Semiconductor device noise Position measurement Integrated circuit measurements Position sensitive particle detectors CMOS process Counting circuits Strips

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Magnetisation and electron spin resonance of the colossal magnetoresistive la0.67Ca0.33Mn1-xFexO3

Magnetisation and electron spin resonance of the colossal ma...

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作者： ZajĄc, T. Folcik, L. Chmist, J. Kolodziejczyk, A. Drulis, H. Krop, K. Gritzner, G. Faculty of Physics and Applied Computer Science AGH University of Science and Technology 30-059 Cracow Poland Institute of Low Temperature and Structure Research Polish Academy of Sciences 50-950 Wroclaw Poland Institut für Chemische Technologie Anorganischer Stoffe Johannes Kepler Universität A-4040 Linz Austria

We report magnetisation and electron spin resonance (ESR) measurements on the colossal magnetoresistive manganites Lao0.67Ca 0.33Mn1-xFexO3, with x = 0, 0.01, 0.03, 0.06, 0.10, and 0.15, in the vicinity of their magnetic (TC) and metal-insulator (TMI) transition temperatures. Above T C, the resonance lines with g 2 are caused by ferromagnetic metallic clusters exhibiting a double exchange interaction between Mn 3+-Mn4+ ions. The lines were observed with cooling far below both TC and TMI, and were fitted by the Dysonian line-shape. The temperature dependences of the line-widths exhibited a minimum value at Tmin 1.25TC, followed by an increase with further cooling toward TC. The anomalous behaviour of the line-width below Tmin is due to the appearance of a ferromagnetic metallic phase within the paramagnetic matrix. The role of phase segregation, in which the compounds are phase-separated into a mixture of ferromagnetic and paramagnetic regions, is discussed.

关键词： Colossal magnetoresistance

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Dependence of the vortex structure in quantum dots on the range of the inter-electron interaction

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Physical Review B 2006年第7期73卷 075315-075315页

作者： T. Stopa B. Szafran M. B. Tavernier F. M. Peeters Departement Fysica Universiteit Antwerpen Groenenborgerlaan 171 B-2020 Antwerpen Belgium Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Kraków Poland

The internal structure of a composite fermion is investigated for a two-dimensional parabolic quantum dot containing three electrons. A Yukawa screened Coulomb interaction is assumed, which allows us to discuss the evolution of the electron-vortex correlations from the Coulomb interaction limit to the contact potential limit. The vortex structure approaches the Laughlin limit nonmonotonically through the formation of intermediate composite fermions in which a flip of the spatial orientation of the vortices with respect to the position of the electrons is observed. Only when we limit ourselves to the lowest Landau level (LLL) approximation the flip appears through the formation of an intermediate giant vortex at specific values of the screening length. Beyond the LLL approximation antivortices appear in the internal structure of the intermediate composite fermions which prevent the nucleation of giant vortices. We also studied the system of five electrons and show that the mechanism of the flip of the vortex orientation found for three-electron system is reproduced for higher number of electrons.

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Charged black holes coupled to non-linear electrodynamics in scalar-tensor theories of gravity with massive scalar field

Charged black holes coupled to non-linear electrodynamics in...

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4th Summer School in Modern Mathematical physics, MPHYS 2006

作者： Stefanov, Ivan Zh. Yazadjiev, Stoytcho S. Todorov, Michail D. Dept. of Theoretical Physics Faculty of Physics University of Sofia St. Kliment Ohridski 5 James Bourchier Blvd. 1164 Sofia Bulgaria Faculty of Applied Mathematics and Computer Science Technical University of Sofia 8 Kliment Ohridski Blvd. 1000 Sofia Bulgaria

The no-scalar-hair theorems do not apply in the case when non-linear electrodynamics is included in the theory. In the current work, some preliminary numerical results describing charged black holes coupled to Born-In... 详细信息

关键词： Electrodynamics

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Topology-dependent interface contribution to magneto-optical response from ultrathin Co films grown on the (001), (110), and (111) surfaces of Pd

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Physical Review B 2006年第8期73卷 085413-085413页

作者： M. Przybylski L. Yan J. Żukrowski M. Nyvlt Y. Shi A. Winkelmann J. Barthel M. Waśniowska J. Kirschner Max-Planck-Institut für Mikrostrukturphysik Weinberg 2 06120 Halle Germany Solid State Physics Department Faculty of Physics and Applied Computer Science AGH University of Science and Technology Mickiewicza 30 30-059 Krakow Poland Faculty of Mathematics and Physics Institute of Physics Charles University Ke Karlovu 5 12116 Praha 2 Czech Republic

We have grown ultrathin epitaxial Co films on three low-index surfaces of Pd. Their magnetic properties studied by the magneto-optical Kerr effect are correlated with the surface morphology analyzed by scanning tunneling microscopy. A perpendicular magnetic anisotropy in the films appeared after exposure to residual gas atmosphere at low temperature, after coverage with an Au overlayer or after annealing at 370K and above. For one- and two-monolayer-thick films the hysteresis loops are reversed with respect to those of thicker Co films. This is due the negative polar Kerr rotation contribution from the Co∕Pd interface dominating over the positive polar Kerr rotation contribution from the noninterface part of the Co film. Reversed loops are not seen when the Co films grow in a three-dimensional mode. This indicates a clear correspondence between the mode of growth and the magneto-optical response. Near the film thickness where the Kerr rotation changes sign a remarkable temperature behavior is observed which is discussed as a superposition of two different magneto-optical contributions. The results qualitatively agree with the available ab initio band-structure calculations for the Co∕Pd multilayer structures with variable thickness of the Co layers.

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Spin- and charge-density waves around Ru impurities in α−Fe alloys studied by Fe57 Mössbauer spectroscopy

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Physical Review B 2006年第10期73卷 104423-104423页

作者： A. Błachowski K. Ruebenbauer J. Żukrowski Mössbauer Spectroscopy Division Institute of Physics Pedagogical University PL-30-084 Cracow ulica Podchorążych 2 Poland Solid State Physics Department Faculty of Physics and Applied Computer Science AGH University of Science and Technology PL-30-059 Cracow Aleja Mickiewicza 30 Poland

A random solid solution of ruthenium in the α-iron has been investigated by means of the Mössbauer spectroscopy using 14.4keV transition in Fe57. Measurements were performed at room temperature versus ruthenium concentration varying up to about 12at.%. Contributions to the iron hyperfine magnetic field and isomer shift due to the ruthenium impurity located at various distances from the resonant iron atom were determined. It was found that these contributions vary in sign depending upon the actual distance from the iron atom. The nearest neighbor ruthenium atom contributes −1.99T. On the other hand, the second neighbor contributes −0.09T, while the third neighbor contributes +0.52T. Corresponding contributions to the isomer shift are as follows: −0.019, +0.072, and +0.005mm∕s. The above behavior is a strong indication for the presence of the spin and charge density waves in the vicinity of the ruthenium impurity in the α-iron.

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