1,720,965 research outputs found
Neutron scattering studies of an antiferromagnetic Kondo compound: Ce8Pd24Ga
No full textThe antiferromagnet Ce8Pd24Ga with TN = 3.1 K has been investigated using neutron diffraction, inelastic neutron scattering, electrical resistivity, magnetoresistance and magnetic susceptibility measurements. Rietveld analysis of neutron diffraction data reveals that Ce8Pd24Ga crystallizes in the cubic structure with space group Pmbar 3m. Inelastic neutron scattering (INS) studies show two well-defined crystal-field excitations at 3.2 meV and 12.8 meV. The crystal-field parameters have been estimated from the analysis of INS data. The heat capacity calculated from the crystal-field level scheme shows a Schottky peak at 15 K which agrees well with the reported experimental results. The resistivity exhibits -ln T behaviour at high temperature followed by a peak at 8 K and eventually drops at TN. The peak in the resistivity at 8 K arises due to the combined effect of crystalline electric fields and Kondo interactions. The analysis of the resistivity data in the magnetically ordered state reveals a gap of 16.1 K in the spin-wave spectrum. At 1.8 K the magnetoresistance is positive and it changes to negative at 3 K. The positive magnetoresistance at 1.8 K is consistent with the antiferromagnetic ground state. The negative magnetoresistance shows a scaling behaviour that yields a low-temperature Kondo temperature of 5.8 K. The magnetic susceptibility exhibits Curie-Weiss behaviour between 20 K and 300 K with an effective paramagnetic moment µeff = 2.33 µB and paramagnetic Curie temperature theta(p) = -18.8 K. The present studies reveal that the physical properties of Ce8Pd24Ga are governed by the Kondo, crystal-field and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions
Magnetic studies of cobalt based granular thin films
Full text linkThe magnetic recording media used for hard disks in laptops and PC's is constantly being improved, leading to rapid increases in data rate and storage density. However, by the year 2010, it is predicted that the superparamagnetic limit will be reached, which is potentially insufficient for data storage. At the beginning of this century, CoCr -based alloys are used in longitudinal media since cobalt has a high magnetocrystalline anisotropy. In this thesis, the static and dynamic properties of longitudinal recording thin films were investigated in order to explain and correlate their magnetic characteristics to their recording properties. The samples in question were test samples and some were in commercial use. Magnetic techniques such as high field ferromagnetic resonance and torque magnetometry were used to determine accurately the crystalline anisotropy field. High field ferromagnetic resonance is an ideal tool to determine the crystalline anisotropy, magnetisation, Lande g-factor and the gyromagnetic damping factor. In contrast to previous work, there are no FMR simulations and so all the relevant parameters were determined directly from measurement. Ideally, there should be no exchange interactions between the neighbouring cobalt grains; however, interactions between the grains within the CoCr-alloy recording layer exist. Previous work on the measurements of interactions in recording media involves measuring the sample's magnetisation. In this thesis, an alternative novel method involves torque magnetometry. Another technique that was used in this thesis is small angle neutron scattering, which aims to determine the size of the magnetic grains and compare that with the physical size determined from TEM, by Seagate. There is an extended section on CoxAg1-x granular thin films, which involves determining the sample's g-factor, effective anisotropy, grain size, exchange constant and comparing the FMR lineshapes at 9.5 and 92GHz
57fe Nmr Study Of Nitrided Ce2fe17
No full textThe 57Fe NMR of Ce2Fe17Nx (x = 0-1.5) was measured in the ordered magnetic state at 4.2 K. For x = 0, resonances coming from all Fe sites have been identified in the 30-45 MHz range. With nitrogenation, new lines appear in the range 37-54 MHz. Every nitrogenated sample shows three sets of lines, arising from regions where Ce atoms have 0, 2, and 3 nitrogen atoms as near neighbors.157-158186188Kapusta, Cz., Rosenberg, M., Riedi, P.C., Katter, M., Schultz, I., (1994) J. Magn. Magn. Mater., 134, p. 106Kapusta, Cz., Rosenberg, M., Zukrowski, J., Figiel, H., Jacobs, T.H., Buschow, K.H.J., (1991) J. Less-common Metals, 171, p. 101Sarthour, R., Gama, S., Colucci, C.C., Lord, J.S., Riedi, P.C., Guimarães, A.P., (1995) J. Magn. Magn. Mater., 140-144, p. 1003Colucci, C.C., Gama, S., (1994) J. Appl. Phys., 75, p. 6003Hu, B.-P., Li, H.-S., Sun, H., Coey, J.M.D., (1991) J. Phys.: Condens. Matter, 3, p. 398
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
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
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
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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