1,720,961 research outputs found
Spin waves in the two-dimensional honeycomb lattice XXZ-type van der Waals antiferromagnet CoPS3
No full text© 2020 American Physical Society. The magnetic excitations in CoPS3, a two-dimensional van der Waals (vdW) antiferromagnet with Co2+ ion on a honeycomb lattice, have been measured using powder inelastic neutron scattering. The absence of spin-orbit exciton around 30 meV indicates that Co2+ ions in CoPS3 have an S = 3/2 state rather than a spin-orbital entangled J(eff) = 1/2 ground state. And, clear dispersive spin waves are observed with a large spin gap of similar to 13 meV. The magnon spectra were fitted using an XXZ-type J(1)-J(2)-J(3) Heisenberg Hamiltonian with single-ion anisotropy assuming no magnetic exchange interaction between the honeycomb layers. The best-fit parameters show ferromagnetic exchange interactions J(1) = -2.08 meV and J(2) = 0.26 meV for the nearest- and second-nearest neighbors and a sizable antiferromagnetic exchange interaction J(3) = 4.21 meV for the third-nearest neighbor with the strong easy-axis anisotropy K = - 2.06 meV. The anisotropic XXZ-type Hamiltonian could only achieve a suitable fitting. The exchange interaction for the out-of-plane spin component is smaller than that for the in-plane one by a ratio alpha = J(2)/J(x) = 0.6. Our result directly shows that CoPS3 is an experimental realization of the XXZ model with a honeycomb lattice in two-dimensional vdW magnets11sciescopu
Effects of Mn-substitution on the valence bond solid in Li2RuO3
No full textLi2RuO3 with a honeycomb structure undergoes a drastic transition from a regular honeycomb lattice with the C2/m space group to a valence-bond solid state of the P2(1)/m space group with an extremely strong dimerization at 550 K. We synthesized Li2Ru1-xMnxO3 with a full solid solution and investigated doping effects on the valence-bond solid state as a function of Mn content. The valence-bond solid state is found to be stable up to x = 0.2, based on our extensive experiments: structural studies, resistivity, and magnetic susceptibility. On the other hand, the extended x-ray absorption fine-structure analyses show that the dimer local structure remains robust even above x = 0.2 with a minimal effect on the dimer bond length. This indicates that the locally disordered dimer structure survives well into the Mn-rich phase even though the thermodynamically stable average structure has the C2/m space group. Our results prove that the dimer formation in Li2RuO3 is predominantly a local phenomenon driven by the formation of orbitally assisted metal-metal bonds and that these dimers are relatively robust against doping-induced disorder.11Nsciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Pressure-induced transition from J(eff)=1/2 to S=1/2 states in CuAl2O4
No full textThe spin-orbit entangled (SOE) J(eff) state has been a fertile ground to study quantum phenomena. Contrary to the conventional weakly correlated J(eff) = 1/2 state of 4d and 5d transition metal compounds, the ground state of CuAl2O4 hosts a J(eff) = 1/2 state with a strong correlation of Coulomb U. Here, we report that, surprisingly, Cu2+ ions of CuAl2O4 overcome the otherwise usually strong Jahn-Teller distortion and instead stabilize the SOE state, although the cuprate has relatively small spin-orbit coupling. From the x-ray absorption spectroscopy and high-pressure x-ray diffraction studies, we obtained definite evidence of the J(eff )= 1/2 state with a cubic lattice at ambient pressure. We also found the pressure-induced structural transition to a compressed tetragonal lattice consisting of the spin-only S = 1/2 state for pressure P-c > 8 GPa. This phase transition from the Mott insulating J(eff) = 1/2 to the S = 1/2 states is a unique phenomenon. Our study offers an example of the SOE J(eff) state under strong electron correlation and its pressure-induced transition to the S = 1/2 state.11Nsciescopu
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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