1,720,967 research outputs found
Visible range colossal magnetorefractive effect in (La-1 (-) Pr-y(y))(2/3)Ca1/3MnO3 films
No full textWe report a colossal magnetorefractive effect (MRE) in epitaxial thin films of a classical colossal magnetoresistance (CMR) manganite, (La-1 (-) Pr-y(y))(2/3)Ca1/3MnO3 (y = 0.375 and 0.7). Close to the ferromagnetic (FM) phase transition a moderate applied magnetic field, H similar to 10 kOe, results in a reduction of the optical reflectance by similar to 18% for the photon energy E similar to 2.7 eV. The MRE spectral behavior with three pronounced maxima at E = 1.6, 2.7 and 4.0eV points out an inter-site nature of the involved optical transitions. The results are discussed within a phase separation scenario with coexisting FM metallic nanodomains antiferromagnetically coupled by correlated polarons. The probability of MRE optical transitions is maximal for antiparallel alignment of Mn3+/Mn4+-spins realized for the coercive field, H-c similar to 200-800 Oe, and is suppressed by stronger fields, which favor FM metallic behavior. As a result, both the optical reflectivity and the electrical resistance decrease, yielding a close similarity between the CMR and MRE behavior.Open Access Publikationsfonds 201
Exchange bias in La0.7Sr0.3MnO3/SrMnO3/La0.7Sr0.3MnO3 trilayers
No full textExchange bias (EB) has been observed for all-manganite La0.7Sr0.3MnO3/SrMnO3/La0.7Sr0.3MnO3 trilayers with ferromagnetic La0.7Sr0.3MnO3 and G-type antiferromagnetic SrMnO3 (SMO) layers, grown on (001) SrTiO3 substrates by metalorganic aerosol deposition. The field shift of the magnetic hysteresis loop H-E and the coercivity H-C decay exponentially with temperature. H-E exhibits a global maximum as a function of SMO interlayer thickness at t(SMO) approximate to 4.5 nm. We argue that EB behaviour can be explained by the interplay of a spinglass state at the interface and theoretically proposed mechanism based on the Dzyaloshinskii-Moriya interaction. (C) 2013 American Institute of Physics
Phase problem in the B-site ordering of La2CoMnO6: impact on structure and magnetism
No full textEpitaxial double perovskite La2CoMnO6 (LCMO) films were grown by metalorganic aerosol deposition on SrTiO3(111) substrates. A high Curie temperature, T-C = 226 K, and large magnetization close to saturation, M-S(5 K) = 5.8 mu(B)/f.u., indicate a 97% degree of B-site (Co,Mn) ordering within the film. The Co/Mn ordering was directly imaged at the atomic scale by scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDX). Local electron-energy-loss spectroscopy (EELS) measurements reveal that the B-sites are predominantly occupied by Co2+ and Mn4+ ions in quantitative agreement with magnetic data. Relatively small values of the (1/2 1/2 1/2) superstructure peak intensity, obtained by X-ray diffraction (XRD), point out the existence of ordered domains with an arbitrary phase relationship across the domain boundary. The size of these domains is estimated to be in the range 35-170 nm according to TEM observations and modelling the magnetization data. These observations provide important information towards the complexity of the cation ordering phenomenon and its implications on magnetism in double perovskites, and similar materials
Interface-controlled magnetism and transport of ultrathin manganite films
No full textWe report ferromagnetic, T-C = 240 K, and metallic, T-MI = 250 K, behaviors of a three unit cell thick interface engineered lanthanum manganite film, grown by metalorganic aerosol deposition technique on SrTiO3(100) substrates. Atomically resolved electron microscopy and chemical analysis show that ultrathin manganite films start to grow with La-O layer on a strongly Mn/Ti-intermixed interface, engineered by an additional deposition of 2 u.c. of Sr-Mn-O. Such interface engineering results in a hole-doped manganite layer and stabilizes ferromagnetism and metallic conductivity down to the thickness of d = 3 u.c. The films with d = 8 u.c. demonstrate a bulk-like transport behavior with T-MI similar to T-C = 310 - 330 K. (C) 2013 American Institute of Physics
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
thin films: field enhancement and depolarization effects
No full textPolarization-dependent tip-enhanced Raman spectroscopy (TERS) was carried out on double perovskite La2CoMnO6 (LCMO) thin films to determine the contributions of the enhancement by the excitation of surface plasmon polariton and tip-induced polarization effects. Due to B-site ordering and the resulting monoclinic P12(1)/n1 structure, the spectra exhibit a strong A(g) mode around 644cm(-1) originated from (Co/Mn)O-6 stretching vibrations. The TERS contrast C, defined as the ratio of the total-field (the sum of the near field and the far field) to the far-field intensity, up to C similar to 60-110 for a cross-polarized configuration (incident light polarization perpendicular to the detected one), reveals a possible breakdown of polarization-dependent selection rules for the Raman scattering due to a tip-induced near-field depolarization component. We disentangled a significant enhancement for all observed modes in a parallel configuration with a TERS contrast of C similar to 2-5 due to general near-field amplification, strongly affected also by the film thickness. With B-site ordering and highly dielectric behavior, LCMO therefore provides an excellent test system to study TERS phenomena on oxide surfaces. Copyright (c) 2016 John Wiley & Sons, Ltd.Deutsche Forschungsgemeinschaft DFG [Sonderforschungsbereich SFB 1073
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
Modeling of colossal magnetoresistance in La0.67Ca0.33MnO3/Pr0.67Ca0.33MnO3 superlattices: Comparison with individual (La1−yPry)0.67Ca0.33MnO3 films
No full textColossal magnetoresistance (CMR) and nm-scale electronic inhomogeneity close to the first order phase transition in perovskite manganites, e.g., (La1-yPry)(0.67)Ca0.33MnO3 still remain a puzzling phenomenon. We experimentally model a metal-insulator phase coexistence by growing a short period (LCMOn/PCMOn)(m) superlattices (SLs) with the same thickness for both components. CMR effect was studied as a function of the individual layer thickness n = 2-8 and then compared with chemically homogeneous (La1-yPry)(0.67)Ca0.33MnO3 LPCMO films. We show that SLs can be superimposed in the phase diagram of LPCMO. The results also point out the importance of the nm-scale electronic rather than chemical separation for realization of the CMR effect as well as limits the lowest boundary for the thickness of an individual manganite material to n similar to 4u.c. (C) 2013 American Institute of Physics
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