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Articoli di riviste sul tema "Light-Induced magnetic effects":
1
Ayadi, M., e J. Ferré. "Light induced magnetic effects in insulating amorphous spin glasses". Journal of Magnetism and Magnetic Materials 54-57 (febbraio 1986): 91–92. http://dx.doi.org/10.1016/0304-8853(86)90499-3.
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A.F. Kabychenkov e F.V. Lisovsky. "Light-induced flexoantiferomagnetic effect in centroantisymmetric antiferromagnets". Technical Physics 92, n. 3 (2022): 369. http://dx.doi.org/10.21883/tp.2022.03.53267.276-21.
Abstract (sommario):
It is shown that an inhomogeneous circularly polarized light wave induces components of the antiferromagnetism vector in centroantisymmetric antiferromagnets; a narrow beam of light can create a skyrmion. The analysis of the possibility of practical use of the predicted effects is carried out. Keywords: optomagnetic effect, polyharmonic light field, light-induced magnetic field, centroantisymmetric antiferromagnet, circularly polarized light wave, flexoantiferromagnetic effect.
3
Liguori, R., e A. Rubino. "Metastable light induced effects in pentacene". Organic Electronics 15, n. 9 (settembre 2014): 1928–35. http://dx.doi.org/10.1016/j.orgel.2014.05.040.
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Betancur, Catalina, Giacomo Dell'Omo e Enrico Alleva. "Magnetic field effects on stress-induced analgesia in mice: modulation by light". Neuroscience Letters 182, n. 2 (dicembre 1994): 147–50. http://dx.doi.org/10.1016/0304-3940(94)90784-6.
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Li, Wenbing, Dong Wan, Guanghua Wang, Lulu Lu e Xiaobi Wei. "Visible light induced photocatalytic degradation of rhodamine B by magnetic bentonite". Water Science and Technology 73, n. 10 (11 febbraio 2016): 2345–52. http://dx.doi.org/10.2166/wst.2016.083.
Abstract (sommario):
The photocatalytic activity of magnetic bentonite, Fe3O4 nanoparticles decorated Al-pillared bentonite (Fe3O4/Al-B), for the degradation of rhodamine B (RhB) in the presence of H2O2 under visible light (VL) was evaluated. The effects of different reaction parameters such as catalyst dose, dye concentration and externally added H2O2 were also investigated. The magnetic bentonite showed good photocatalytic activity, magnetic separability and stability for repeated use. More than 95% of 40 mg/L RhB was converted within 3 h under VL with a catalyst dose of 0.5 g/L. Suitable mechanisms have been proposed to account for the photocatalytic activities in the presence and absence of H2O2. The efficiency of H2O2 in VL process was much higher than that of the dark process. Results obtained in the current study may be useful to develop a suitable photocatalyst for photocatalytic remediation of different water contaminants including organic dyes.
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Pardavi-Horváth, M., P. E. Wigen e P. DeGasperis. "Light-induced time-dependent electrical and magnetic effects in charge-uncompensated Ca2+: YIG". Journal of Magnetism and Magnetic Materials 83, n. 1-3 (gennaio 1990): 425–26. http://dx.doi.org/10.1016/0304-8853(90)90571-7.
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MOTOC, CORNELIA, e GABRIELA IACOBESCU. "MAGNETO-OPTIC EFFECTS IN NEMATIC LIQUID CRYSTAL DOPED WITH AZO-DYES". Modern Physics Letters B 20, n. 17 (30 luglio 2006): 1015–22. http://dx.doi.org/10.1142/s0217984906011013.
Abstract (sommario):
Nematic liquid crystal cells were subjected to different DC magnetic fields and the optical transmission of a He-Ne laser beam was recorded for different field values. It was found that a small addition of Methyl Orange (MO) induced optical activity into the nematic sample. When the cells were subjected to increasing magnetic field, the rotatory power (rotation angle) varied periodically; the same occurred for the light transmission and ellipticity. We found that the light emerging from the liquid crystal cell is elliptically polarized and in some cases circularly polarized. After UV light irradiation (365 nm) the rotatory power of the sample increases. The position of rotation angle maxima and minima is slightly affected by the irradiation.
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Wang, Bing-Yen, Sheng-Yang Huang, Ya-Shing Hsiao, Pei-Ching Wei, Chia-Man Chou e Vincent K. S. Hsiao. "Pulsed-Laser Induced Photolysis of Synthesizing Magnetic Fe3O4 Nanoparticles for Visible-Light Photocatalysis". Catalysts 12, n. 11 (17 novembre 2022): 1459. http://dx.doi.org/10.3390/catal12111459.
Abstract (sommario):
Our report is the first example describing the successful synthesis of magnetic Fe3O4 nanoparticles (NPs), for which we used pulsed-laser induced photolysis (PLIP). Compared with the previous method of using pulsed-laser ablation of a target, or strong energy of pulsed-laser light to decompose precursors in generating a solvated-ion reaction, the PLIP method used here is dependent on hydrogen peroxide (H2O2) to generate a hydrolysis reaction. Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were used to demonstrate the Fe3O4 crystalline structure of the synthesized NPs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the average size of the NPs was about 20–50 nm. Regarding their magnetic characteristics, the synthesized NPs exhibited a saturation magnetization of 5.62 emu/g, remanence of 3.82 emu/g, and coercive force of 49.8 Oe. The photocatalytic experiments confirmed that the synthesized magnetic Fe3O4 NPs have visible light-degradation effects based on their ability to photocatalytically degrade methylene blue (MB). The MB degradation efficiency was 60–80% under white-light exposure for 180 min. This study presents a new route for synthesizing magnetic Fe3O4 NPs for their potential use in photocatalysis.
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Shukla, P. K., R. Fedele, M. Onorato e N. L. Tsintsadze. "Envelope solitons induced by high-order effects of light-plasma interaction". European Physical Journal B - Condensed Matter 29, n. 4 (1 ottobre 2002): 613–18. http://dx.doi.org/10.1140/epjb/e2002-00344-1.
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Zellama, Kacem, J. David Cohen e Thomas Walsh. "Capacitance studies of light induced effects in undoped a-Si:H". Journal of Non-Crystalline Solids 77-78 (dicembre 1985): 381–84. http://dx.doi.org/10.1016/0022-3093(85)90679-9.
Tesi sul tema "Light-Induced magnetic effects":
1
Real, Elgueda Bastián Maximiliano. "Transport and driven-dissipative localization in exciton-polariton lattices". Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR025.
Abstract (sommario):
La simulation des Hamiltoniens de réseaux dans les plateformes photoniques a permis de mieux comprendre les nouvelles propriétés de transport et de localisation dans le contexte de la physique de l'état solide. En particulier, les exciton-polaritons constituent un système polyvalent permettant d'étudier ces propriétés dans des réseaux avec des structures de bande intrigantes en présence de pertes et de gains, et d'interactions entre particules. Les polaritons sont des quasi-particules hybrides lumière-matière résultant du couplage fort entre les photons et les excitons dans les microcavités semi-conductrices, dont les propriétés peuvent être directement accessibles dans les expériences de photoluminescence. Dans cette thèse, nous étudions premièrement les caractéristiques des réseaux en nid d'abeille déformés, composés de résonateurs de polaritons couplés, à haut contenu photonique. Dans un réseau déformé de façon critique, nous mettons en évidence à la fois un transport semi-Dirac et une localisation anisotrope des photons. Deuxièmement, nous montrons qu'un forçage judicieux dans des réseaux de résonateurs à pertes permet l'apparition de nouveaux modes localisés. En utilisant des réseaux de polaritons sous un forçage résonant par plusieurs faisceaux optiques, nous démontrons la possibilité de localiser la lumière sur différentes géométries, voir jusqu'à un seul site. Enfin, nous profitons de l'interaction de polaritons dépendant de la polarisation pour démontrer un effet optique de type Zeeman dans un seul micropilier. En combinant le couplage spin-orbite optique, inhérent aux microstructures semi-conductrices, avec l'effet Zeeman, induit par l'interaction, nous montrons l'émission de faisceaux de vortex avec une chiralité bien définie. Cette thèse met en lumière la puissance des plateformes de polaritons pour étudier les Hamiltoniens de réseaux avec des propriétés sans précédent. Elle apporte également un premier pas vers la génération, entièrement optique, de phases topologiques dans les réseauxThe simulation of lattice Hamiltonians in photonic platforms has been enlightening in the understanding of novel transport and localization properties in the context of solid-state physics. In particular, exciton-polaritons provide a versatile system to investigate these properties in lattices with intriguing band structures in the presence of gain and loss, and particle interactions. Polaritons are hybrid light-matter quasiparticles arising from the strong coupling between photons and excitons in semiconductor microcavities, whose properties can be directly accessed in photoluminescence experiments. In this thesis, we firstly study the features of strained honeycomb lattices made of coupled polariton resonators having high photonic content. In a critically strained lattice, we evidence both a semi-Dirac transport and an anisotropic localization of photons. Secondly, we show that a judicious driving in lattices of lossy resonators allows the appearance of novel localized modes. Using polariton lattices driven resonantly with several optical beams, we demonstrate the localization of light in at-will geometries down to a single site. Finally, we take advantage of the polarization-dependent polariton interaction to demonstrate an optical Zeeman-like effect in a single micropillar. In combination with optical spin-orbit coupling inherent to semiconductor microstructures, the interaction-induced Zeeman effect results in emission of vortex beams with a well-defined chirality. This thesis brings to light the power of polariton platforms to study lattice Hamiltonians with unprecedented properties and it also provides a first step towards the fully-optical generation of topological phases in lattices
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Guo, Wenbin. "Nouveaux composés à conversion de spin et polymorphisme pour une approche multi-échelle vers les hautes T(LIESST)". Thesis, Bordeaux, 2021. http://www.theses.fr/2021BORD0015.
Abstract (sommario):
L'effet LIESST (Light-Induced Excited Spin-State Trapping) apparaît comme l'un des phénomènes les plus prometteurs et les plus excitants pour les dispositifs applicatifs basés sur les complexes à transition de spin (TS). Cependant, la compréhension fondamentale du LIESST doit encore être approfondie avant toute conception rationnelle. Par exemple, il est encore très difficile d'établir les relations structure-propriétés, bien que cette approche soit cruciale pour découvrir des matériaux à TS ayant une température de relaxation T(LIESST) élevée. L'objectif de ce travail est donc de comprendre comment augmenter la valeur de T(LIESST) vers une plage de température de la vie quotidienne. Nous avons choisi de l’atteindre en tentant d’augmenter la distorsion de la sphère de coordination du métal par deux stratégies basées sur la chimie : i) influer à l'échelle moléculaire via des contraintes stériques induites par des ligands halogénés et ii) moduler la contrainte moléculaire via du polymorphisme. La partie I présente quelques aspects fondamentaux et les parties II et III sont consacrées à la synthèse, à la cristallographie et aux études (photo)magnétiques des nouveaux composés moléculaires, y compris des polymorphes, de la famille [Fe(PM-L)2(NCX)2]. Ces nouveaux composés offrent tout d'abord un large éventail de comportements innovants, comme par exemple des expansions volumiques négatives ou nulles à la TS et l'absence de transition à plusieurs étapes malgré des sites métalliques indépendants au sein du cristal. Ces travaux élargissent considérablement la richesse des perspectives du phénomène de TS. De plus, l'examen approfondi des paramètres pertinents pour l’obtention d’un T(LIESST) élevé, tel que discutés dans la partie IV, apporte de nouvelles caractéristiques et prouve définitivement que toutes les échelles physiques doivent être prises en compte, ce qui conduit à proposer un concept multi-échelle de l'effet LIESSTThe Light-Induced Excited Spin-State Trapping effect (LIESST) appears as one of the most promising and exciting phenomena for applicative devices based on Spin-CrossOver (SCO) complexes. However, the fundamental understanding of the LIESST effect must be yet deeply completed prior to any rational design of any efficient material. For instance, it is still a great challenge to establish the structure-properties relationships corresponding to the LIESST process, though this approach is crucial to discover SCO materials with a high relaxation temperature T(LIESST). The target of this work is therefore to understand how to increase T(LIESST) towards a daily-life temperature range. We choose to reach this goal by increasing the distortion of the metal coordination sphere through two chemistry-based strategies: i) playing at the molecular scale via steric strains produced by halogen-substituted ligands and ii) controlling the molecular stress through polymorphism. Part I displays some fundamental knowledge on SCO and Part II and III are devoted to the synthesis, crystallography and (photo)magnetic studies of new molecular compounds, including polymorphs, of the [Fe(PM-L)2(NCX)2] family. First these new compounds offer a large panel of innovative behaviours, such as, for instance, negative or zero volume expansions at the SCO and the absence of multi-step transition despite independent metal sites within the crystal. This work enlarges significantly the richness of the SCO based perspectives. Second, the deep examination of the relevant parameters to high T(LIESST) as discussed in Part IV brings new features and, overall, definitively proves that all physical scales must be taken into account, leading to a multiscale concept of the LIESST effect
3
Bhattarai, Mangesh. "Light and magnetic field induced coherence effects in atoms". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4932.
Abstract (sommario):
In this thesis, we have studied the coherence effects in atoms induced by light and a magnetic field. After giving an introduction to the contents of the thesis, details about the theory and the experimental setup used are given. The next few chapters contain the experimental results backed by a theoretical understanding. Only the joint work with the Armenian group (paper titled “Study of EIT resonances in an anti-relaxation coated Rb vapor cell” published in Physics Letters A) is one where they did the experiment and we did the theory. The thesis ends with a discussion about the various results presented.
In the first work, the magnetic field induced coherence effect is studied in the light of the Hanle effect. We have studied the transformation of a Hanle EIT to a Hanle EIA for a circularly polarized beam in presence of a spatially separated control beam whose ellipticity is varied. A density matrix model describing three regions of interaction is developed to reproduce the experimental results.
The second work describes the use of CPT/EIT system in a double-lambda configuration to interfere beams in one lambda system while the other lambda system acts as a phase reference. This process of light interference mediated by atomic coherence is extended to propose a system in which interference between two beams 10s of GHz apart in frequency could be detected on a low bandwidth (10s of MHz) optical detector.
The third work describes an observation of EIA in a vee + ladder system in 87Rb. The vee system is formed by using the D1 line of 87Rb as control and the D2 line as the probe, and the ladder system is formed by the same probe as in vee system and a beam on the transition from 5P3/2 to 5D5/2 as control.
The fourth work, done along with our collaborators in Armenia, shows splitting of EIT into dark and bright resonance in the presence of a strong transverse magnetic field in an anti-relaxation coated cell in the D1 line of 87Rb. We have performed a density matrix analysis using all the magnetic sublevels to reproduce the experimental results. The tunability of such a system between super-luminal and sub-luminal propagation for a probe beam is also theoretically discussed.
Libri sul tema "Light-Induced magnetic effects":
1
Adapa, Ram, e Anthony Absalom. Central nervous system physiology in anaesthetic practice. A cura di Jonathan G. Hardman. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0006.
Abstract (sommario):
How and where consciousness is generated and maintained remains an unsolved scientific mystery, and this has impeded progress in understanding anaesthesia. In recent years, however, significant progress has been made in understanding the neurobiology of anaesthetic-induced loss of consciousness. This has been made possible by advances in molecular biology techniques, which have helped shed light on the molecular mechanisms of action of the anaesthetic agents. In parallel, the development of neuroimaging techniques, such as functional magnetic resonance imaging and positron emission tomography, has also provided an enormous impetus. These techniques are providing new insights into the neural correlates of consciousness, and new insights into the alterations in neurophysiology associated with impaired consciousness caused by sleep, sedation, and anaesthesia. The information being gained from these studies on the neurobiology of impairments of attention, awareness, and memory will hopefully eventually not only lead to improvements in our understanding of consciousness and anaesthesia, but also to better clinical care. Understanding of memory functions during sedation and anaesthesia may, for example, lead to better strategies for preventing awareness with subsequent explicit recall of intraoperative events. Further, a better understanding of the neurobiology of anaesthetic-induced unconsciousness may inform future development of better anaesthetic agents, with a broader therapeutic index, and fewer unwanted effects.
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Rai, Dibya Prakash, a cura di. Advanced Materials and Nano Systems: Theory and Experiment - Part 2. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/97898150499611220201.
Abstract (sommario):
The discovery of new materials and the manipulation of their exotic properties for device fabrication is crucial for advancing technology. Nanoscience, and the creation of nanomaterials have taken materials science and electronics to new heights for the benefit of mankind. Advanced Materials and Nanosystems: Theory and Experiment covers several topics of nanoscience research. The compiled chapters aim to update students, teachers, and scientists by highlighting modern developments in materials science theory and experiments. The significant role of new materials in future technology is also demonstrated. The book serves as a reference for curriculum development in technical institutions and research programs in the field of physics, chemistry and applied areas of science like materials science, chemical engineering and electronics. This part covers 12 topics in these areas: 1. Recent advancements in nanotechnology: a human health Perspective 2. An exploratory study on characteristics of SWIRL of AlGaAs/GaAs in advanced bio based nanotechnological systems 3. Electronic structure of the half-Heusler ScAuSn, LuAuSn and their superlattice 4. Recent trends in nanosystems 5. Improvement of performance of single and multicrystalline silicon solar cell using low-temperature surface passivation layer and antireflection coating 6. Advanced materials and nanosystems 7. Effect of nanostructure-materials on optical properties of some rare earth ions doped in silica matrix 8. Nd2Fe14B and SmCO5: a permanent magnet for magnetic data storage and data transfer technology 9. Visible light induced photocatalytic activity of MWCNTS decorated sulfide based nano photocatalysts 10. Organic solar cells 11. Neodymium doped lithium borosilicate glasses 12. Comprehensive quantum mechanical study of structural features, reactivity, molecular properties and wave function-based characteristics of capmatinib
Capitoli di libri sul tema "Light-Induced magnetic effects":
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Lippmann, Morton, Beverly S. Cohen e Richard B. Schlesinger. "Nonionizing Electromagnetic Radiation". In Environmental Health Science, 310–30. Oxford University PressNew York, NY, 2003. http://dx.doi.org/10.1093/oso/9780195083743.003.0010.
Abstract (sommario):
Abstract Electromagnetic radiation is emitted from sources in space and from anthropogenic sources on earth. It travels at a constant speed, i.e., the speed of light. The overall electromagnetic spectrum is illustrated in Figure 10–1. Energy is transmitted as a sinusoidal wave form, by time varying electric and magnetic fields. The transmission velocity, c, is described by the formula: The health effects of exposures to the various components of the electromagnetic spectrum vary greatly with frequency, and the discussion that follows outlines the sources, as well as the nature and extent of the effects that they produce. There are separate discussions on component bands within the overall spectrum, i.e., ionizing radiation, UV, visible, IR, and radio frequency (RF). The electric and magnetic fields induced by these radiations can also produce biological responses, and these responses will also be reviewed.
2
Castel, B., e I. S. Towner. "Single-Particle and Shell-Model Theories of Quadrupole Moments". In Modern Theories of Nuclear Moments, 188–211. Oxford University PressOxford, 1990. http://dx.doi.org/10.1093/oso/9780198517283.003.0006.
Abstract (sommario):
Abstract We now turn our attention to electric quadrupole moments. These moments have traditionally been invoked as good indicators of collective effects in contrast to magnetic moments. The reason for that is simple and has to do with the difference in the nature of the two relevant operators. The magnetic dipole operator leads to opposite contributions from a state |ψ⟩ and its time-reversed conjugate |ψ˜⟩ (since both currents and spin change sign in the |ψ⟩→|ψ˜⟩ conjugation). Thus one member of the paired-off nucleon cancels the contribution from the other. Such is not the case for the quadrupole operator since its contributions are invariant under time reversal. Thus if nuclear correlations can be induced by some deformation, a coherent buildup of quadrupole moment can be expected. As we shall see, this coherence can lead to sizeable effects which will be examined in this chapter in the light of single-particle and various shell models. The next chapter will be devoted to a survey of the macroscopic models currently available for the study of quadrupole moments and nuclear deformations.
3
Shahinpoor, Mohsen. "Shape Memory Polymers (SMPs) as Smart Materials". In Fundamentals of Smart Materials, 160–69. The Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/bk9781782626459-00160.
Abstract (sommario):
Chapter 14 reviews shape memory polymers (SMPs). Shape memory polymers belong to the family of shape memory materials (SMMs), which can be deformed into a predetermined shape under some imposed specific conditions such as temperature, electric or magnetic field, as well as strain and stress. These shapes can be relaxed back to their original field-free shapes under thermal, electrical, magnetic, strain, stress, temperature, laser, or environmental stimuli. These transformations are essentially due to the elastic energy stored in SMMs during initial deformation. As a member of SMMs, SMPs are stimuli-sensitive polymers. Shape memory polymers normally use either heat or laser light energy as a stimulant to change shape. The thermally-induced shape memory effect can be observed by irradiation with infrared light, exposure to alternating magnetic fields, application of an electric field or immersion in water.
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Freeman, Ray. "Detection of magnetic resonance". In Magnetic Resonance in Chemistry and Medicine, 33–53. Oxford University PressOxford, 2003. http://dx.doi.org/10.1093/oso/9780199260614.003.0003.
Abstract (sommario):
Abstract We first observe the magnetic resonance response from the nuclei as a tiny voltage induced on a coil surrounding the sample-the receiver coil. How does this arise? In most forms of spectroscopy there are three possible mechanisms to describe the interaction of radiation with matter. Stimulated absorption or stimulated emission describe the absorption or emission of radiation by the sample provoked by the radiation field itself. Spontaneous emission occurs in the absence of any imposed radiation field, for example, the light emitted from a heated metallic filament. Spontaneous emission is far too weak an effect to be relevant to magnetic resonance experiments. The free precession NMR signal occurs after extinction of the radiofrequency pulse used for excitation and subsequently evolves in the absence of any imposed radiation field, so none of these three phenomena can properly account for magnetic resonance signals.
Atti di convegni sul tema "Light-Induced magnetic effects":
1
Davidenko, I. I., M. Fally, R. A. Rupp e B. Sugg. "Magnetic and Optical Anisotropy in Garnets Induced by Linearly Polarized Light". In Photorefractive Effects, Materials, and Devices. Washington, D.C.: OSA, 2001. http://dx.doi.org/10.1364/pemd.2001.528.
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Sochava., S. L., e S. I. Stepanov. "Non-steady-state Photocurrent in GaAs in the Presence of an External Magnetic Field". In Photorefractive Materials, Effects, and Devices II. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/pmed.1993.fre.2.
Abstract (sommario):
Excitation of an alternating through current inside a photoconductive crystal illuminated by an. oscillating interference patυβrn was first- observed in 1986 [1). It is caused by a time-dependent phase shift between the free carrier and space charge field distributions.. Investiga tions of this current give information about such important parameters of the light-induced charge transfer as the sign of ths charge carriei3, diffusion length, M-xwell relaxation time, free charge carrier lifetime, etc. Originally this so-called "non-steady-state photocurrent technique was proposed to characterize the sillenite type crystals (BSO). Later it was used for investigation of semiconductor GaAs [2] and ferroelectric EaTiOj [3] crystals. In this contribution we report the first, to our knowledge, results of the study of the non-steady-state photocurrent ir the presence of an external magnetic field.
3
Briat, B. "Magnetic Circular Dichroism Study of Intrinsic and Impurity Centers in Bi12MO20 (M=GE,Ti,Si) : an Overview". In Photorefractive Materials, Effects, and Devices II. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/pmed.1993.fre.4.
Abstract (sommario):
What are the defects or impurities responsible for the photorefractive effect in Bii2MO2o (BMO 6:1)? What happens during illumination at various wavelengths? What are the microscopic centers, either diamagnetic or paramagnetic, responsible for ±e intrinsic or light / impurity induced absorption bands? One must obviously try to answer such questions if one wants to understand the observed effects and to optimize the materials for improved performances. Since 1990 *, we have conducted a systematic spectroscopic study of photochromic effects in a large variety of undoped and doped BMO 6:1 crystals of two origins As already briefly demonstrated in previous communications χ3.4, magnetic circular dichroism (MCD) offers an elegant and powerful means for a microscopic study of charge transfer processes and the identification of donnor/acceptor levels. The technique has also long been established 5 as an invaluable tool (i) to characterize the charge state and local environment of a doping rm nation metal ion; (ii> to discriminate among paramagnetic and diamagnetic centers. MCD can be defined as the differential absorption Δα (cm4) for left and right circularly polarized light when the sample is subπüted to a longitudinal magnetic field B. In zero field, BMO crystals present also a natural CD which contains interesting information. My goal here is to present an overview of our most significant results since the Aussois Topical Meeting. Quite naturally, MCD.and CD spectra have been complemented by low temperature absorption experiments in the visible and near IR regions. Note that previous CD 6,7 and MCD 8 work on BMO materials, although scarce, has all been conducted in Eastern Europe.
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Silverman, M. P. "Test of gyrotropic constitutive relations by specular light reflection". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.fs7.
Abstract (sommario):
Gyrotropic media are generally characterized by skew symmetric (electric) permittivity and (magnetic) permeability tensors. There is wide belief, however, as expressed In both expository and research literature, that only the permittivity takes a tensorial form for intrinsically nonmagnetic materials whose electrooptic behavior is of interest. I show that neglect or inclusion of light-induced magnetic anisotropy leads to qualitatively different physical predictions (even in the simplest case of an isotropic optically active medium) for gyrotropic effects manifested in specular reflection from the surface of the medium rather than in light propagation through the interior of the medium. In particular, differential reflection of circularly polarized light differs markedly as a function of incident angle, reaching peak value either beyond Brewster angle or near normal incidence, depending on whether a tensorial or scalar expression, respectively, relates vectors H and B. A scalar relation also leads to internal inconsistencies such as slight violations of energy conservation. The differences in constitutive relations are most significant on implementation of electromagnetic boundary conditions. This accounts for why light-induced magnetic anisotropy Influences differential light reflection but not optical rotation or circular dichroism.
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Sablong, R., E. Grillon, O. Hugon e J. Derouard. "Non invasive optical monitoring of rat brain and effects of the injection of tracers for blood flow measurements". In European Conference on Biomedical Optics. Washington, D.C.: Optica Publishing Group, 2001. http://dx.doi.org/10.1364/ecbo.2001.4432_236.
Abstract (sommario):
Near infrared spectroscopy using either broad band reflectance spectrophotometry or monochromatic illumination has been carried out to monitor non invasively the changes of the concentrations of chromophores in rat brain induced by the intravenous injection of various contrast agents (indocyamne green, ultrasmall magnetic particles suspension, albumine, dextran, or saline solution alone). Depending of the wavelength and of the absorption spectrum of the injected compound the bolus can be seen either by a decrease or an increase of the transmitted light, this latter due to induced dilution of the blood by the bolus. We suggest that this could be used to determine the arterial input function the contrast agent needed to perform absolute cerebral blood flow imaging by nuclear magnetic resonance.
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Wang, Hongbo, e William S. Oates. "A Phase Field Model of Photo-Induced Trans-Cis-Trans Bending of Liquid Crystal Elastomer Films". In ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2010. http://dx.doi.org/10.1115/smasis2010-3657.
Abstract (sommario):
A new class of glassy liquid crystal elastomers are studied to understand their light-coupled deformation characteristics. In particular, the photomechanics of azobenzene liquid crystal elastomers is modeled using a nonlinear continuum mechanics approach coupled with time-dependent liquid crystal domain structure evolution to understand light polarization effects on deformation. Light propagation and absorption within the elastomer is modeled using Maxwell’s electro-magnetic equations. By consideration of electric energy due to light absorption, light-induced electrical stresses are introduced which provide the driving force for mechanical deformation via coupling with the azobenzene liquid crystals. A liquid crystal director (i.e., orientation of the liquid crystal molecule) is used to describe liquid crystal evolution and elastomer deformation. This aspect of the model is extended to include 3D effects to accommodate trans-cis-trans photoisomerization. This is coupled to plane stress, nonlinear mechanics to demonstrate key field-coupled mechanics relations governing this class of smart materials. The results show that the model successfully predicts large, bi-directional bending of the polymer film by controlling the polarization of light. The results are consistent with recent experimental data given in the literature.
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Boardman, A. D., e Xie Kang. "Nonlinear reflection of TM polarized plane waves and beams by a magneto-optic interface". In Integrated Photonics Research. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/ipr.1990.wc6.
Abstract (sommario):
The reflectivity of the TM wave from magneto-optic nonlinear interfaces between magnetized films of media like nickel, iron, or YIG bounded by a nonmagnetic, nonlinear substrate or cladding, or mixed with nonmagnetic, nonlinear films is calculated for the widely used1,2ATR configuration. The results mainly concern prism coupling but with the much less studied third-order nonlinear TM polarization3 being used. Progress toward extending the theory to include gratings is also discussed, however. Traditionally, magnetic-field orientations include transverse, polar, and longitudinal orientations, and these are the principal ones analyzed here. Longitudinal orientations involve some complex and novel nonlinear calculations because in such a case, even in the linear limit, TM and TE polarizations cannot be decoupled so that a linear Kerr rotation of the plane of polarization occurs. Questions concerning the optimum signal-to-noise ratio are addressed in order to try and arrange the highest value to coincide with the resonant angle positions. In this connection detailed comments on the trade-off between nonlinear and magneto-optic effects are given. Nonlinear ATR curves, the power flow along the surface, the first-order magneto-optical parameter, and the magnetic-field-induced rotation of the plane of polarization are all calculated for both plane waves and for finite beams with nonlocal nonlinearity. Again, because the latter is a difficult calculation to perform, the method alone is of great interest. The simpler transverse case can be cited as an example here. The ATR curves, as might be expected, break into branches at critical power levels, but this now feeds through into the relative change of the reflected intensity of light owing to the magnetization of the film. Any sharp decrease in this first-order magneto-optic quantity is now delayed by the nonlinearity, and a critical light intensity causes two or more branches to appear. For this same case we show that the forward field reflectivity actually switches to a second branch a little earlier than for the reverse field direction; hence, the resonance angles are not matched. Finally, comments on the exploitation of nonlinear magneto-optic effects in thin-film guided-wave geometries are included.
8
KUBO, TOSHIHIRO, e YASUHIRO TOKURA. "MANY-BODY EFFECTS ON TUNNELING OF ELECTRONS IN MAGNETIC-FIELD-INDUCED QUASI ONE-DIMENSIONAL SYSTEMS IN QUANTUM WELLS". In Proceedings of the International Symposium on Mesoscopic Superconductivity and Spintronics — In the Light of Quantum Computation. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812701619_0007.
9
Tsai, Chen S., C. L. Wang e Y. Pu. "Bismuth-doped yttrium iron garnet-gadolinium gallium garnet waveguides with application to magneto-optic Bragg cells". In Integrated Photonics Research. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/ipr.1990.tud1.
Abstract (sommario):
Similar to guided-wave acousto-optic (AO) interactions1 in which the surface acoustic waves (SAWs) induce a moving optical grating through the photoelastic effect, guided-wave magneto-optic (MO) interactions result from the moving optical grating induced by the magnetostatic waves (MSW) through the Faraday and the Cotton-Mouton effects.2 Of particular interest to us is a noncollinear coplanar geometry2 in YIG-GGG waveguides,3 as shown in Fig. 1 in which an incident guided-light wave is Bragg diffracted and mode-converted (TE- to TM-mode and vice versa). The Bragg-diffracted light is scanned in the waveguide plane as the frequency of the MSW is tuned. Analogous to the AO Bragg diffraction in which the resulting modulator is called the AO Bragg cell, the resulting MO modulator is called the MO Bragg cell.2
10
Rahman, Mosfequr, Masud Nawaz e John E. Jackson. "Experimental Investigation on the Use of Photostrictive Optical Actuator for MEMS Devices and Verification With the FEA Modeling Results". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65581.
Abstract (sommario):
Photostrictive materials are lanthanum-modified lead zirconate titanate (Pb, La)(Zr, Ti) O3 ceramics doped with WO3, called PLZT, exhibit large photostriction under uniform illumination of high-energy light. Photostrictive materials are ferrodielectric ceramics that have a photostrictive effect. Photostriction arises from a superposition of the photovoltaic effect, i.e. the generation of large voltage from the irradiation of light, and the converse-piezoelectric effect, i.e. expansion or contraction under the voltage applied. When non-centrosymmetric materials, such as ferroelectric single crystals or polarized ferroelectric ceramics, are uniformly illuminated, a high voltage, considerably exceeding the band gap energy, is generated. Along with this photovoltage, mechanical strain is also induced due to the converse piezoelectric effect. Photostrictive materials offer the potential for actuators with many advantages over traditional transducing electromechanical actuators made of shape memory alloys and electroceramics (piezoelectric and electrostrictive). Drawback of traditional actuators is that they require hard-wired connections to transmit the control signals which introduce electrical noise into the control signals; on the other hand PLZT actuators offer non-contact actuation, remote control, and immune from electric/magnetic disturbances. Some experimental research has been conducted on the use of PLZT materials, such as optical motor as an electromechanical device suitable for miniaturization, micro-waking machine, photo driven relay device using PLZT bimorphs and high speed (less than 10 ns), low-voltage, low power consumption optical switch. Authors have developed a computational method and implemented in an in-house finite element code which will be useful for designing systems incorporating thin film photostrictive actuators. The purpose of this current research work is to design and develop an experimental test set-up for photostriction effect measurement of PLZT thin film of different thickness, size and location on silicon wafer as smart beams, which may be useful for various MEMS device as optical actuator. The experimental results will be verified by comparing with the FEA modeling results.
Rapporti di organizzazioni sul tema "Light-Induced magnetic effects":
1
Johra, Hicham. Performance overview of caloric heat pumps: magnetocaloric, elastocaloric, electrocaloric and barocaloric systems. Department of the Built Environment, Aalborg University, gennaio 2022. http://dx.doi.org/10.54337/aau467469997.
Abstract (sommario):
Heat pumps are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water production. Conventional heat pumps are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The heat pump market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional heat pumps can have a large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression heat pump technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining large attention. These caloric effects are characterized by a phase transition varying entropy in the material, resulting in a large adiabatic temperature change. This phase transition is induced by a variation of a specific external field applied to the solid refrigerant. Therefore, the magnetocaloric, elastocaloric, electrocaloric and barocaloric effects are adiabatic temperature changes in specific materials when varying the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. Heat pump cycle can be built from these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not a mature technology yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and domestic hot water production. This technical report (and the paper to which this report is supplementary materials) aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression heat pumps for building applications.