1,720,981 research outputs found
La4Co4 ( =Pb, Bi, Sb): a demonstration of antagonistic pairs as a route to quasi-low dimensional ternary compounds
Full text linkWe outline how pairs of strongly immiscible elements, referred to here as antagonistic pairs, can be used to synthesize ternary compounds with quasi-reduced dimensional motifs. By identifying third elements that are compatible with a given antagonistic pair, ternary compounds can be formed in which the third element segregates the immiscible atoms into spatially separated substructures. Quasi-low dimensional structural units are a natural consequence of the immiscible atoms seeking to avoid contact in the solid-state. As proof of principle, we present the discovery and physical properties of La4Co4X (X = Pb, Bi, Sb), a new family of intermetallics based on the antagonistic pairs Co-Pb and Co-Bi. La4Co4X adopts a new orthorhombic crystal structure (space group Pbam) containing quasi-2D Co slabs and La-X layers that stack along the a-axis. Consistent with our proposal, the La atoms separate the Co and X substructures, ensuring there are no direct contacts between immiscible atoms. Within the Co slabs, the atoms occupy the vertices of corner sharing tetrahedra and triangles, and this motif produces flat electronic bands near the Fermi level that favor magnetism. The Co is moment bearing in La4Co4X, and we show that whereas La4Co4Pb behaves as a three dimensional antiferromagnet with TN = 220 K, La4Co4Bi and La4Co4Sb have behavior consistent with low dimensional magnetic coupling and ordering, with TN = 153 K and 143 K respectively. In addition to the Pb, Bi, and Sb based La4Co4X compounds, we were likely able to produce an analogous La4Co4Sn in polycrystalline form, although we were unable to isolate single crystals. We anticipate that using mutually compatible third elements with an antagonistic pair represents a generalizable design principle for discovering new materials and structure types containing low-dimensional substructures.This is a preprint from Slade, Tyler J., Nao Furukawa, Matthew Dygert, Siham Mohamed, Atreyee Das, Weiyi Xia, Cai-Zhuang Wang, Sergey L. Budko, and Paul C. Canfield. "La 4 Co 4 X (X= Pb, Bi, Sb): a demonstration of antagonistic pairs as a route to quasi-low dimensional ternary compounds." arXiv preprint arXiv:2403.00204 (2024). doi: https://doi.org/10.48550/arXiv.2403.00204. Published as Slade, Tyler J., Nao Furukawa, Matthew Dygert, Siham Mohamed, Atreyee Das, Weiyi Xia, Cai-Zhuang Wang, Sergey L. Bud'ko, and Paul C. Canfield. "La 4 Co 4 X (X= Pb, Bi, Sb): A demonstration of antagonistic pairs as a route to quasi-low-dimensional ternary compounds." Physical Review Materials 8, no. 6 (2024): 064401. doi: https://doi.org/10.1103/PhysRevMaterials.8.064401
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Strong Anharmonicity at the Origin of Anomalous Thermal Conductivity in Double Perovskite Cs2 NaYbCl6
Full text linkAnomalous thermal transport of Cs2 NaYbCl6 double-halide perovskite above room temperature is reported and rationalized. Calculations of phonon dispersion relations and scattering rates up to the fourth order in lattice anharmonicity have been conducted to determine their effective dependence on temperature. These findings show that specific phonon group velocities and lifetimes increase if the temperature is raised above 500 K. This, in combination with anharmonicity, provides the microscopic mechanism responsible for the increase in lattice thermal conductivity at high temperatures, contrary to the predictions of phonon transport theories based on solely cubic anharmonicity. The model accurately and quantitatively reproduces the experimental thermal conductivity data as a function of temperature
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Vacancy Tuned Magnetism in LaMnSb2
Full text linkThe layered ATMPn2 (A = alkali earth or rare earth atom, TM = transition metal, Pn = Sb, Bi) compounds are widely studied for their rich magnetism and electronic structure topology. Here, we characterize the physical properties of LaMnxSb2, an understudied member of the ATMPn2 family. LaMnxSb2 forms with intrinsic Mn vacancies, and we demonstrate synthetic control of the Mn occupancy to produce single crystals with x = 0.74-0.97. Magnetization and transport measurements indicate LaMnxSb2 has a rich temperature-composition (T-x) magnetic phase diagram with physical properties strongly influenced by the Mn occupancy. LaMnxSb2 orders antiferromagnetically at T1 = 130--180 K, where T1 increases with x. Below T1, the T-x phase diagram is complicated. At high x, there is a second transition T2 that decreases in temperature as x is lowered, vanishing below x ≤ 0.85. A third, first-order, transition T3 is detected at x ≈ 0.92, and the transition temperature increases as x is lowered, crossing above T2 near x ≈ 0.9. On moving below x Published as Slade, Tyler J., Aashish Sapkota, John M. Wilde, Qiang Zhang, Lin-Lin Wang, Saul H. Lapidus, Juan Schmidt, Thomas Heitmann, Sergey L. Bud'Ko, and Paul C. Canfield. "Vacancy-tuned magnetism in LaMn x Sb 2." Physical Review Materials 7, no. 11 (2023): 114203. doi: https://doi.org/10.1103/PhysRevMaterials.7.114203
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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