23,467 research outputs found
Magneto–Optical Kerr Effect Microscopy Investigation on Permalloy Nanostructures
No full textThis thesis focuses on the investigation of magnetic domains in ultrasmall permalloy (Ni80Fe20) structures down to nanometre size. Magnetic domains and domain walls in nano objects are often observed using a very high resolution and high power microscope such as magnetic soft x-ray microscope, magnetic force microscopy imaging and photoemission electron microscopy. A reason for this is because the Kerr signal in nanostructures is very weak. However the results from this thesis demonstrate that magnetic domains in permalloy magnetic nanostructures can still be observed with very good contrast using a Magneto-optical Kerr effect (MOKE) microscope. The constructed Kerr microscope is a home-build wide field microscope and is able to produce magnetic domains image of permalloy nanowire as small as 245 nm, although the resolution limit of the microscope is 505 nm. For the first time, a magnetic domain in nanowire with width of 245 nm is observed using a wide-field microscope. The combination of hysteresis loops and magnetic domains observations for studying a magnetic sample provides a three-dimensional understanding of the magnetic characteristic of the sample. This is crucial in investigating nano samples as the theoretical arguments with the experimental results are always constrained by the experimental part. Three kinds of nanostructure sample were observed using the Kerr microscope; a cross nanowire, zigzag nanowire and a nanowire with notch and a nucleation pad at one end. It was found that a cross nanowire can form magnetic domains upon reversal and the junction forms a magnetisation vortex. Findings from zigzag nanowire demonstrate a complex, multiple magnetic domains formation upon magnetisation reversal. A weak domain wall pinning effect was observed in the nanowire, causing a multiple domains formation in the nanowire upon reversal. It can be confirmed that this effect was caused by the high coercivity of the nucleation pad. For the nanowire with notch, it was demonstrated that the coercivities were different at negative and positive field. But for such case, there is a relationship observed between the percentage notch depth and the coercivity at the junction
Food Safety Incidents, Collateral Damage and Trade Policy Responses: China-Canada Agri-Food Trade
No full textAs markets become globalized, food safety policy and international trade policy are increasingly intertwined. Globalization also means that food safety incidents are widely reported internationally. One result is that food safety incidents can negatively impact products where no food safety issue exists as consumers lose trust in both foreign and domestic food safety institutions. While the policy framework for dealing with directly effected imported foods is well understood, how to deal with the market failure associated with indirectly affected products within the existing trade policy rules has not been explored. Using the example of China’s 2007 problems with a spate of products safety incidents, a theoretical framework is developed and the response of both the Chinese and Canadian governments analyzed. A cooperative approach to the issues appears to have a number of advantages and does not contravene trade policy commitments.Canada, China, cooperation, food safety, market failure, trade policy, Agricultural and Food Policy, International Development, International Relations/Trade,
CE Challenges: Work to Do
No full textCE has been used for more than two decades now. Despite many successes and advantages, there are still many challenges to be addressed. These challenges are both technical and organisational. In the paper we will address the current challenges of CE. Many challenges are related to the exchange of data and knowledge and to the systems that make data and knowledge exchange possible. Although much progress has been made in enabling extensive data and knowledge exchange and use, much remains to be wished. For example, there are still barriers to data exchange. Technically, these barriers may consist of different formats, differences in infrastructures and systems, and different semantics. There are also organisational and political barriers. For example, investment in information system may heavily impact upstream suppliers, while revenues of better information exchange may predominantly be gained by downstream actors. Without sharing costs and revenues, chain-wide information exchange will not be easily realised. Another barrier is the possible lack of willingness to share information, because of potential misuse of knowledge and loss of power. The paper is organised as follows. First we will describe the current manifestation of CE as described in a recent book. Second, we will list current trends in CE. Third, we will present some Critical Success Factors (CSFs) that are considered relevant for implementing and adapting CE practices. Last, we indicate some research and practical questions to be addressed, especially for areas that have a high potential and actual impact. </p
MAGNETIC PROPERTIES AND KERR ROTATION IN AMORPHOUS Ce-Fe AND Pr-Fe ALLOYS
No full textSeveral amorphous Ce-Fe and Pr-Fe alloys were prepared by means of vapour-deposition and their magnetic properties were studied. The Ce1-xFex alloys are ferromagnetic with magnetic ordering temperatures below room temperature, even for Fe concentrations as high as 90 at% Fe. In the Pr1-xFex alloys magnetic ordering appears to be more complex than ferromagnetic. Magnetic ordering temperatures are in excess of room temperature. At low temperatures the intrinsic coercive force is appreciable. At higher temperature it decreases strongly according to the relation IHc-1αT. Due to the low ordering temperature the room temperature Kerr rotation is very low in Ce1-xFex. Much higher values are observed in Pr1-xFex. Here the concentration dependence of the Kerr rotation gives rise to a maximum near 80 at% Fe
Synthesis optimization and charge carrier transfer mechanism in LiLuSiO<sub>4</sub>:Ce, Tm storage phosphor
No full textLiLuSiO4:Ce and LiLuSiO4:Ce, Tm show very efficient charge carrier storage properties upon beta irradiation after samples have received treatment in vacuum. They outperform the commercial storage phosphor BaFBr(I):Eu2+ in many aspects. The influence of the synthesis conditions, Ce and Tm concentration, nonstoichiometry and codoping with Ca, Hf, Al and Ge are reported. Based on the results of the synthesis optimization, thermoluminescence (TL) emission and TL excitation spectra a mechanism of charge carrier transfer, storage, and recombination during irradiation and thermal or optical readout is proposed.Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Luminescence Material
Element-specific magnetization reversal in Fe/Ce multilayers: a study by X-ray magnetic circular dichroism and the magneto-optic Kerr effect
No full textFe/Ce multilayers are magnetically soft with coercive fields of a few Oersteds. In this artificial system, the itinerant 5d electrons of Ce are magnetically polarized by hybridization with the spin-split 3d states of Fe. To obtain an insight into the magnetization reversal process, the element selectivity of X-ray magnetic circular dichroism was used to measure the magnetization of the Ce-Sd electrons as a function of an applied magnetic field. Comparison with the magnetization curves studied by the magneto-optic Kerr effect, which averages over the whole system, revealed that the coercivity in the hysteresis of the ordered Ce-Sd moments is reduced by 50%. We propose that this is an effect of the magnetically disturbed interface or of the complex non-collinear magnetic structure of the Ce layers detected by recent experiments of X-ray resonant magnetic scattering. The results are compared to the X-ray dichroic and Kerr hysteresis loops of the multilayers Fe/La/Ce/La and Fe/CeH2-delta. These systems are magnetically harder and their coercivities are identical. (C) 2000 Elsevier Science B.V. All rights reserved
The impact of P(NDI2OD-T2) crystalline domains on the open-circuit voltage of bilayer all-polymer solar cells with an inverted configuration
No full textWe fabricated P(NDI2OD-T2)/PTB7 bilayer all-polymer solar cells with an inverted configuration, where the annealing temperature was systematically varied. The current density-voltage behavior was investigated and the structural properties of the P(NDI2OD-T2) layers were characterized. Absorption spectroscopy, surface morphology, and crystallite analysis showed that increasing phase segregation of P(NDI2OD-T2) films occurred as the annealing temperature increased. We found that, as the P(NDI2OD-T2) stacking improved, with larger domains, the open-circuit voltage decreased and the saturation dark current density increased. This work provides a guide for the processing of P(NDI2OD-T2) layers to maximize the power conversion efficiency of all-polymer solar cells. (C) 2015 Author(s).open1186sciescopu
Magneto-optical Kerr Effect of Gd-Co Amorphous Films
No full textThe magneto-optical Kerr effect of Gd-Co films prepared by rf magnetron sputtering is investigated for films with Gd concentration from about 10% to 50% within a wavelength range of 400∿1000[nm]. The Kerr rotation θ_K is well approximatd by a formura θ_K=C_|M_|+C_|M_| within a compositional range studied, where C_ and C_ are Kerr rotation coefficients depending only on the wavelength and M_ and M_ are subnetwork magnetizations of Co and Gd, rspectively. The spectra for C_ and C_ are determind, which depend only slightly on the wavelength with values of about -0.3 [deg/T] for C_ and -0.045 [deg/T] for C_ at 600 [nm]. It is also found that the magneticmoment of Co atom in the Gd-Co alloy decreases very slowly with increasing Gd concentration, the fact which is far different from the cases of other RE-Co films of RE=La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, and Tm
On the nature of the absolute maximal observable magneto-optical Kerr rotation of CeSb
No full textWe report first-principles calculations of
the polar magneto-optical (MO) Kerr spectra of the Ce compounds
CeSb, , CeTe, and CeSe,
using the
local-density approximation (LDA) of density-functional theory
as well as its generalization which contains
an explicit Coulomb interaction U
(LDA+U).
Although the LDA predicts a large Kerr rotation of about 20
in CeSb, we find that
the LDA+U
gives a better description of the Kerr spectra of all four compounds.
For CeSb the LDA+U predicts a colossal
Kerr rotation of 45 up to 60,
in agreement with the recent discovery of the maximal observable
rotation
of 90 in CeSb by
Pittini et al. (Phys. Rev. Lett., 77 (1996) 944).
The origin of the colossal Kerr rotation realized in CeSb is examined
Data and code for: Variational Graph Author Topic Modeling
No full textThis is the tensorflow implementation of KDD-2022 paper "Variational Graph Author Topic Modeling" by Delvin Ce Zhang and Hady W. Lauw.
VGATM is a Graph Neural Network model that extracts interpretable topics for documents with authors and venues. Topics of documents then fulfill document classification, citation prediction, etc.
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