1,721,088 research outputs found
Domain wall displacement by current pulses injection in submicrometer Permalloy square ring structures
No full textThe magnetoresistance in submicrometer Permalloy square ring structures has been experimentally measured and modeled. The authors show that using an external field they can place a head-to-head domain wall at a selected corner of the ring and sense its position by magnetoresistance. They finally demonstrate that a domain wall can be reversibly and controllably displaced by current pulses of different polarity. Their observations can be explained by a directional spin-torque effect
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
Vortex rotation control in Permalloy disks with small circular voids
No full textWe studied the magnetization reversal of Permalloy disks with a small circular void either concentric or decentered. In both systems the reversal takes place via the nucleation and annihilation of a magnetic vortex. By applying the diffracted magneto-optic technique combined with numeric micromagnetic simulations we retrieved the information about the sense of rotation of the magnetization in the vortex state. For the disks with the concentric void no preferential rotation has been observed. For the case of decentered void, the sense of rotation of all probed disks is deterministically controlled by appropriately choosing the direction of the externally applied field and the void position with respect to the disk center
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
Chirality and stability of vortex state in Permalloy triangular ring micromagnets
No full textWe present the results of a study of the magnetization reversal in Permalloy triangular rings using diffracted magneto-optics Kerr effect combined with numerical micromagnetic simulations and in-field magnetic force microscopy. Diffracted loops show a two-step switching process for external fields along or perpendicular to any of the ring edges. The diffracted loops calculated from micromagnetic simulations reproduce the measured ones and show that the switching occurs from one asymmetric onion state to the reversed state, for both directions of the applied field. In both cases a stable intermediate vortex state appears during the switching, accounting for the diffracted loop structures. The stability and the magnetization chirality of the vortex state depend on the direction of the applied field relative to the ring orientation. Magnetization configurations occurring during reversal imaged with magnetic force microscopy operated applying an external field confirm the above reversal process
Magnetoresistance of single Permalloy circular rings
No full textWe have measured magnetoresistance in single, 1 mm external diameter, Permalloy (Ni80Fe20) circular rings with varied inner holediameter of 150, 300, and 600nm and film thickness of 25 nm. The Permalloy ring structures and the 10-nm-thick, 250-nm-wide Aunanocontacts were fabricated on a SiO2/Si substrate using e-beam lithography. Using a four contact geometry we studied the dependenceof the magnetoresistance on the direction of the applied field. The experimental data are explained by considering only the conventionalanisotropic magnetoresistance effect. Numerical simulations of the current distribution within the samples combined with micromagneticsimulations of the field dependent magnetization profile, yield good agreement with the experimental data. Upon increasing the innerhole diameter (viz. decreasing the ring width) the magnetoresistance measurements show a transition of the reversal process from the‘‘vortex nucleation–displacement–annihilation’’ sequence to the ‘‘onion state–reversed onion state’’ sequence, typical of narrownanorings.r 2007 Elsevier B.V. All rights reserved
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