Academic literature on the topic 'Magnetised vortex'
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Journal articles on the topic "Magnetised vortex"
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Shelyag, S., V. Fedun, F. P. Keenan, R. Erdélyi, and M. Mathioudakis. "Photospheric magnetic vortex structures." Annales Geophysicae 29, no. 5 (May 23, 2011): 883–87. http://dx.doi.org/10.5194/angeo-29-883-2011.
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Abstract. Using direct numerical magneto-hydrodynamic (MHD) simulations, we demonstrate the evidence of two physically different types of vortex motions in the solar photosphere. Baroclinic motions of plasma in non-magnetic granules are the primary source of vorticity in granular regions of the solar photosphere, however, there is a significantly more efficient mechanism of vorticity production in strongly magnetised intergranular lanes. These swirly motions of plasma in intergranular magnetic field concentrations could be responsible for the generation of different types of MHD wave modes, for example, kink, sausage and torsional Alfvén waves. These waves could transport a relevant amount of energy from the lower solar atmosphere and contribute to coronal plasma heating.
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Lega, E., A. Morbidelli, R. P. Nelson, X. S. Ramos, A. Crida, W. Béthune, and K. Batygin. "Migration of Jupiter mass planets in discs with laminar accretion flows." Astronomy & Astrophysics 658 (January 27, 2022): A32. http://dx.doi.org/10.1051/0004-6361/202141675.
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Context. Migration of giant planets in discs with low viscosity has been studied recently. Results have shown that the proportionality between migration speed and the disc’s viscosity is broken by the presence of vortices that appear at the edges of the planet-induced gap. Under some conditions, this ‘vortex-driven’ migration can be very slow and eventually stops. However, this result has been obtained for discs whose radial mass transport is too low (due to the small viscosity) to be compatible with the mass accretion rates that are typically observed for young stars. Aims. Our goal is to investigate vortex-driven migration in low-viscosity discs in the presence of radial advection of gas, as expected from angular momentum removal by magnetised disc winds. Methods. We performed three dimensional simulations using the grid-based code FARGOCA. We mimicked the effects of a disc wind by applying a synthetic torque on a surface layer of the disc characterised by a prescribed column density ΣA so that it results in a disc accretion rate of ṀA = 10−8 M⊙ yr−1. We have considered values of ΣA typical of the penetration depths of different ionising processes. Discs with this structure are called ‘layered’ and the layer where the torque is applied is denoted as ‘active’. We also consider the case of accretion focussed near the disc midplane to mimic transport properties induced by a large Hall effect or by weak Ohmic diffusion. Results. We observe two migration phases: in the first phase, which is exhibited by all simulations, the migration of the planet is driven by the vortex and is directed inwards. This phase ends when the vortex disappears after having opened a secondary gap, as is typically observed in vortex-driven migration. Migration in the second phase depends on the ability of the torque from the planet to block the accretion flow. When the flow is fast and unimpeded, corresponding to small ΣA, migration is very slow, similar to when there is no accreting layer in the disc. When the accretion flow is completely blocked, migration is faster (typically ṙp ~ 12 AU Myr−1 at 5 au) and the speed is controlled by the rate at which the accretion flow refills the gap behind the migrating planet. The transition between the two regimes, occurs at ΣA ~ 0.2 g cm−2 and 0.65 g cm−2 for Jupiter or Saturn mass planets at 5.2 au, respectively. Conclusions. The migration speed of a giant planet in a layered protoplanetary disc depends on the thickness of the accreting layer. The lack of large-scale migration apparently experienced by the majority of giant exoplanets can be explained if the accreting layer is sufficiently thin to allow unimpeded accretion through the disc.
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Liu, Jixing, and Wendell Horton. "The intrinsic electromagnetic solitary vortices in magnetized plasma." Journal of Plasma Physics 36, no. 1 (August 1986): 1–24. http://dx.doi.org/10.1017/s0022377800011557.
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Several Rossby-type vortex solutions constructed for electromagnetic perturbations in magnetized plasma encounter the difficulty that the perturbed magnetic field and the parallel current are not continuous on the boundary between two regions. We find that fourth-order differential equations must be solved to remove this discontinuity. Special solutions for two types of boundary value problem for the fourth-order partial differential equations are presented. By applying these solutions to different nonlinear equations in magnetized plasma, the intrinsic electromagnetic solitary drift-Alfvén vortex (along with solitary Alfvén vortex) and the intrinsic electromagnetic solitary electron vortex (along with short-wavelength drift vortex) are constructed. While still keeping a localized dipole structure, these new vortices have more complicated radial structures in the inner and outer regions than the usual Rossby-wave vortex. The new type of vortex guarantees the continuity of the perturbed magnetic field δB⊥ and the parallel current j‖ on the boundary between inner and outer regions of the vortex. The allowed regions of propagation speeds for these vortices are analysed, and we find that the complementary relation between the vortex propagating speeds and the corresponding phase velocities of the linear modes no longer exists.
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Kono, M., B. Krane, H. L. Pécseli, and J. Trulsen. "Vortex Dynamics in Magnetized Plasmas." Physica Scripta 58, no. 3 (September 1, 1998): 238–45. http://dx.doi.org/10.1088/0031-8949/58/3/008.
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Maslov, V. I., O. K. Cheremnykh, A. P. Fomina, R. I. Kholodov, O. P. Novak, and R. T. Ovsiannikov. "Vortex Structures and Electron Beam Dynamics in Magnetized Plasma." Ukrainian Journal of Physics 66, no. 4 (May 12, 2021): 310. http://dx.doi.org/10.15407/ujpe66.4.310.
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We investigate the formation of vortex structures at the refl ection of an electron beam from the double layer of the Jupiter ionosphere. The infl uence of these vortex structures on the formation of dense upward electron fl uxes accelerated by the double layer potential along the Io flux tube is studied. The phase transition to the cyclotron superradiance mode becomes possible for these electrons. The conditions of the formation of vortex perturbations are considered. The nonlinear equation that describes the vortex dynamics of electrons is constructed, and its consequences are studied.
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Russell, Craig L., P. J. Blennerhassett, and P. J. Stiles. "Strongly nonlinear vortices in magnetized ferrofluids." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 40, no. 2 (October 1998): 146–70. http://dx.doi.org/10.1017/s0334270000012443.
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AbstractNonlinear convective roll cells that develop in thin layers of magnetized ferrofluids heated from above are examined in the limit as the wavenumber of the cells becomes large. Weakly nonlinear solutions of the governing equations are extended to solutions that are valid at larger distances above the curves of marginal stability. In this region, a vortex flow develops where the fundamental vortex terms and the correction to the mean are determined simultaneously rather than sequentially. The solution is further extended into the nonlinear region of parameter space where the flow has a core-boundary layer structure characterized by a simple solution in the core and a boundary layer containing all the harmonics of the vortex motion. Numerical solutions of the boundary layer equations are presented and it is shown that the heat transfer across the layer is significantly greater than in the conduction state.
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Bergmans, J., B. N. Kuvshinov, V. P. Lakhin, T. J. Schep, and E. Westerhof. "Current-vortex filaments in magnetized plasmas." Plasma Physics and Controlled Fusion 41, no. 3A (January 1, 1999): A709—A717. http://dx.doi.org/10.1088/0741-3335/41/3a/064.
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MAMUN, A. A. "Nonlinear propagation of dust-acoustic waves in a magnetized dusty plasma with vortex-like ion distribution." Journal of Plasma Physics 59, no. 3 (April 1998): 575–80. http://dx.doi.org/10.1017/s002237789800645x.
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A theoretical investigation has been made of the nonlinear propagation of dust-acoustic waves in a magnetized three-component dusty plasma consisting of a negatively charged dust fluid, free electrons and vortex-like distributed ions. It is found that, owing to the departure from the Boltzmann ion distribution to a vortex-like one, the dynamics of small- but finite-amplitude dust-acoustic waves in a magnetized dusty plasma is governed by the modified Korteweg–de Vries equation. The latter admits a stationary dust-acoustic solitary-wave solution that has larger amplitude, smaller width and higher propagation velocity than that involving adiabatic ions. The effects of external magnetic field, trapped ions and free electrons on the properties of these dust-acoustic solitary waves are briefly discussed.
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SHUKLA, P. K., T. FARID, L. STENFLO, and O. G. ONISHCHENKO. "Sheared-flow-driven vortices in a magnetized dusty electron–positron plasma." Journal of Plasma Physics 64, no. 4 (October 2000): 427–31. http://dx.doi.org/10.1017/s0022377800008667.
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It is shown that sheared plasma flows can generate nonthermal electrostatic waves in a magnetized dusty electron–positron plasma. Linearly excited modes attain large amplitudes and start interacting among themselves. Nonlinearly coupled modes self-organize in the form of coherent vortices comprising a vortex chain and a double vortex. Conditions under which the latter appear are given. The relevance of our investigation to space, astrophysical, and laboratory plasmas is pointed out.
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Khizar, M., Arshad M. Mirza, M. Salahuddin, and M. S. Qaisar. "Magnetic electron drift vortex in magnetized plasma." Physica Scripta 55, no. 5 (May 1, 1997): 599–603. http://dx.doi.org/10.1088/0031-8949/55/5/012.
Full textDissertations / Theses on the topic "Magnetised vortex"
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Meglicki, Zdzislaw, and Zdzislaw Meglicki [gustav@perth ovpit indiana edu]. "Analysis and Applications of Smoothed Particle Magnetohydrodynamics." The Australian National University. Research School of Physical Sciences, 1995. http://thesis.anu.edu.au./public/adt-ANU20080901.114053.
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Smoothed Particle Hydrodynamics (SPH) is analysed as the weighted residual method. In particular the analysis focuses on the collocation aspect of the method. Using Monte Carlo experiments we demonstrate that SPH is highly sensitive to node disorder, especially in its symmetrised energy and momentum conserving form. This aspect of the method is related to low [Beta] MHD instabilities observed by other authors. A remedy in the form of the Weighted Differences Method is suggested, which addresses this problem to some extent, but at a cost of losing automatic conservation of energy and momentum.
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The Weighted Differences Method is used to simulate propagation of Alfven and magnetosonic wave fronts in [Beta] = 0 plasma, and the results are compared with data obtained with the NCSA Zeus3D code with the Method of Characteristics (MOC) module.
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SPH is then applied to two interesting astrophysical situations: accretion on to a white dwarf in a compact binary system, which results in a formation of an accretion disk, and gravitational collapse of a magnetised vortex. Both models are 3 dimensional.
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The accretion disk which forms in the binary star model is characterised by turbulent flow: the Karman vortex street is observed behind the stream-disk interaction region. The shock that forms at the point of stream-disk interaction is controlled by the means of particle merges, whereas Monaghan-Lattanzio artificial viscosity is used to simulate Smagorinsky closure.
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The evolution of the collapsing magnetised vortex ends up in the formation of an expanding ring in the symmetry plane of the system. We observe the presence of spiralling inward motion towards the centre of attraction. That final state compares favourably with the observed qualitative and quantitative characteristics of the circumnuclear disk in the Galactic Centre. That simulation has also been verified with the NCSA Zeus3D run.
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In conclusions we contrast the result of our Monte Carlo experiments with the results delivered by our production runs. We also compare SPH and Weighted Differences against the new generation of conservative finite differences methods, such as the Godunov method and the Piecewise Parabolic Method. We conclude that although SPH cannot match the accuracy and performance of those methods, it appears to have some advantage in simulation of rotating flows, which are of special interest to astrophysics.
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Cass, Ann C. "Experiments on vortex symmetrization in magnetized electron plasma columns /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9906488.
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Martin, Norbert. "Herstellung und Charakterisierung von magnetisch heterogenen Schichten und Elementen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-78070.
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In der vorliegenden Dissertation wurden magnetisch heterogene, weichmagnetische Schichten hergestellt und in ihren magnetischen Eigenschaften gezielt modifiziert. Zu Beginn wurden in makroskopischen Bereichen Strukturen mit lateral in Streifen modulierter magnetischer Anisotropie im Mikrometermaßstab hergestellt, um den Einfluss der inneren Grenzflächen auf die magnetische Hysterese zu charakterisieren. Dazu wurden über Ionenimplantation in einer funktionalen Deckschicht lokal zusätzliche mechanische Spannungen generiert, ohne die intrinsischen Eigenschaften der magnetischen Schicht zu verändern. Mit der entwickelten Methode können rein über das gezielte Induzieren mechanischer Spannungen hybride magnetische Eigenschaften mit periodisch alternierenden, magnetisch leichten Achsen erzeugt werden.
Im mesoskopischen Bereich beeinflussen zusätzlich die äußere Form und die Größe der magnetisch heterogenen Elemente die magnetischen Eigenschaften. In dieser Dissertation wurde für streifenstrukturierte Quadrate ein analytisches Modell entwickelt, um die Wechselwirkungen von Grenzflächen innerhalb der Elemente und der lateralen Elementgrenzen auf das Ummagnetisierungsverhalten zu simulieren. Das modellierte Ummagnetisierungsverhalten wurde mit experimentell gemessenen Daten unterlegt und bestätigt. Im Vergleich zwischen Modell und Experiment zeigte sich, dass die Größe der externen Felder, bei denen die Magnetisierung innerhalb der Elemente schaltet, voneinander abweicht. Dies ist bedingt durch die bevorzugte Nukleation magnetischer Domänen an den lateralen Begrenzungen der quadratischen Elemente.
Ein Aspekt, der die Nukleation von Domänen wesentlich beeinflusst, ist die Form der lateralen Begrenzung. Durch gezielte Manipulation des Kantenwinkels wurde das Ummagnetisierungsverhalten weichmagnetischer Kreisscheiben gesteuert. Dabei nukleiert der für Kreisscheiben charakteristische Vortexzustand bevorzugt in Elementen mit abgeschrägten Kanten.
Die Gesamtheit der Daten zeigt, dass die magnetischen Eigenschaften heterogener Strukturen nicht nur von den Eigenschaften der Ausgangsmaterialien abhängen, sondern entscheidend von den Größen und Formen der Strukturierungen und der Elemente bestimmt werden.
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Kayali, Mohammad Amin. "Spontaneous vortex phase and pinning in ferromagnetic-superconducting systems." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/409.
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Heterogeneous ferromagnetic-superconducting systems such as a regular array of ferromagnetic nano dots deposited on the top of a superconducting thin film have attracted many research teams both experimental and theoretical. The interest in these systems does not only stem from being good candidates for technological applications, but also because they represent a new class of physical systems where two competing order parameters can coexist. This work focuses on the theoretica laspects of these systems by studying the static and dynamics of few model systems. In the first part, the static properties of a superconducting thin film interacting with a ferromagnetic texture are considered within the London approximation. In particular, the ferromagnetic textures considered here are a circular dot of submicrometer size with in-plane magnetization, an elliptical dot magnetized in the direction perpendicular to the superconductor, and a ferromagnetic dot magnetized in the direction normal to the superconducting film and containing non magnetic cavities. I also consider the interaction of vortices in the superconductor with a ferromagnetic columnar defect which penetrates the supercondcting film. In each case the vector potential and magnetic field of the ferromagnet in the presence of the superconductor are calculated. Afterward the presence of vortices in the superconductor is assumed and the energy of vortex-texture system is found. The pinning potential and force supplied by the texture are then derived from the energy of interaction between the ferromagnet and superconductor. I show that if the magnetization of the ferromagnet exceeds a critical value then vortices are spontaneously created in the ground state of the system. Such spontaneous creation of vortices is possible mostly in a close vicinity of the superconducting transition temperature Ts. For every case, the threshold value of the magnetization at which vortices start to be spontaneously created in the SC is calculated as a function of the parameters of the texture geometry. The phase diagrams for transitions from vortexless regime to regimes with one or more vortices are determined for all cases. In the second problem, the transport properties of a ferromagnetic superconducting bilayer with alternating magnetization and vortex density are studied within a phenomenological model. I show that pinning forces do not appear for continuous distribution of vortices, so a discrete model for the bilayer system is constructed. Afterward, I calculate the pinning forces acting on vortices and antivortices resulting from highly inhomogeneous distribution of flux lines and prove that this system has strong transport anisotropy. In the absence of random pinning, the system displays a finite resistance for the current in the direction perpendicular to the domains while its resistance vanishes for the parallel current. The transport anisotropy strongly depends on temperature. I study this dependence and show that the ratio of parallel to perpendicular critical current is largest close to the superconducting transition temperature Ts and the vortex disappearance temperature Tv while it has a minimum in between them.
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Mejia-Ariza, Raquel. "Design, Synthesis, and Characterization of Magnetite Clusters using a Multi Inlet Vortex Mixer." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/45432.
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Superparamagnetic nanoparticles have potential applications in targeted drug delivery and as magnetic resonance imaging contrast agents. Magnetite clusters are of particular interest for these applications because they provide higher magnetic flux (under a magnetic field) than individual magnetite nanoparticles, are biocompatible, and their size and compositions can be controlled. This thesis involves the controlled synthesis and characterization of clusters composed of magnetite nanoparticles stabilized with an amphiphilic block copolymer. It outlines a method to design and form well-defined and colloidally stable magnetite clusters. A Multi Inlet Vortex mixer (MIVM) was used because it is a continuous process that yields particles with relatively narrow and controlled size distributions. In the MIVM, four liquid streams collide under turbulent conditions in the mixing chamber where clusters form within milliseconds. The formation of magnetite clusters was studied in the presence of amphiphilic block copolymers containing poly (ethylene oxide) to provide steric stabilization and control of size distributions using flash nanoprecipitation.
First, the mixer was tested using β-carotene as a model compound to form nanoparticles stabilized with an amphiphilic triblock copolymer poly(propylene oxide)-b-poly(ethylene oxide) (F127) at different Reynolds numbers and supersaturation values. Size analysis was done using dynamic light scattering and nanoparticle tracking analysis techniques. The cluster structure was studied using electron microscopy and magnetite compositions were measured using thermogravimetric analysis. Finally, the stability of magnetite clusters was studied over time and the effect of an applied magnetite field on the colloidal stability was investigated.Master of Science
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Cherepov, Sergiy. "Resonant switching and vortex dynamics in spin-flop bi-layers." Doctoral thesis, KTH, Nanostrukturfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27193.
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This thesis is a study of the static and dynamic behavior of the magne-tization in spin-flop bi-layers, which consist of two soft ferromagnetic layerscoupled by dipolar forces through a thin nonmagnetic spacer. The focus ofthe work is three fold: collective spin dynamics in the anti-parallel groundstate; resonant switching in the presence of thermal agitation; and static anddynamic behavior of the system in the vortex-pair state, with a particularemphasis on the interlayer core-core interaction. Two collective spin-flop resonance modes are observed and interpreted asacoustical and optical spin precessions, in which the moments of the two lay-ers oscillate in phase and out of phase, respectively. An analytical macrospinmodel is developed to analyze the experimental results and is found to ac-curately predict the resonance frequencies and their field dependence in thelow-field anti-parallel state and the high-field near saturated state. A micro-magnetic model is developed and successfully explains the static and dynamicbehavior of the system in the entire field range, including the C- and S-typespin-perturbed scissor state of the bi-layer at intermediate fields. The optical spin-flop resonance at 3-4 GHz is used to demonstrate resonantswitching in the system, in the range of the applied field where quasi-staticswitching is forbidden. An off-axis field of relatively small amplitude canexcite large-angle scissor-like oscillations at the optical resonance frequency,which can result in a full 180-degree reversal, with the two moments switchingpast each other into the mirror anti-parallel state. It is found that the switch-ing probability increases with increasing the duration of the microwave fieldpulse, which shows that the resonant switching process is affected by thermalagitation. Micromagnetic modeling incorporating the effect of temperature isperformed and is in good agreement with the experimental results. Vortex pair states in spin-flop bi-layers are produced using high amplitudefield pulses near the optical spin resonance in the system. The stable vortex-pair states, 16 in total, of which 4 sub-classes are non-degenerate in energy, areidentified and investigated using static and dynamic applied fields. For AP-chirality vortex-pair states, the system can be studied while the two vortexcores are coupled and decoupled in a single field sweep. It is found thatthe dynamics of the AP-chirality vortex pairs is critically determined by thepolarizations of the two vortex cores and the resulting attractive or repulsivecore-core interaction. The measured spin resonance modes in the system areinterpreted as gyrational, rotational, and vibrational resonances with the helpof the analytical and micromagnetic models developed herein. A significant effort during this project was made to build two instrumentsfor surface and transport characterization of magnetic nanostructures: a high-current Scanning Tunneling Microscope for studying transport in magneticpoint contacts, and a Current In Plane Tunneling instrument for characteriz-ing unpatterned magnetic tunnel junctions. The design and implementationof the instruments as well as the test data are presented.QC 20101209
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Edström, Alexander. "Theoretical and Computational Studies on the Physics of Applied Magnetism : Magnetocrystalline Anisotropy of Transition Metal Magnets and Magnetic Effects in Elastic Electron Scattering." Doctoral thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304666.
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In this thesis, two selected topics in magnetism are studied using theoretical modelling and computational methods. The first of these is the magnetocrystalline anisotropy energy (MAE) of transition metal based magnets. In particular, ways of finding 3d transition metal based materials with large MAE are considered. This is motivated by the need for new permanent magnet materials, not containing rare-earth elements, but is also of interest for other technological applications, where the MAE is a key quantity. The mechanisms of the MAE in the relevant materials are reviewed and approaches to increasing this quantity are discussed. Computational methods, largely based on density functional theory (DFT), are applied to guide the search for relevant materials. The computational work suggests that the MAE of Fe1-xCox alloys can be significantly enhanced by introducing a tetragonality with interstitial B or C impurities. This is also experimentally corroborated. Alloying is considered as a method of tuning the electronic structure around the Fermi energy and thus also the MAE, for example in the tetragonal compound (Fe1-xCox)2B. Additionally, it is shown that small amounts (2.5-5 at.%) of various 5d dopants on the Fe/Co-site can enhance the MAE of this material with as much as 70%. The magnetic properties of several technologically interesting, chemically ordered, L10 structured binary compounds, tetragonal Fe5Si1-xPxB2 and Hexagonal Laves phase Fe2Ta1-xWx are also investigated. The second topic studied is that of magnetic effects on the elastic scattering of fast electrons, in the context of transmission electron microscopy (TEM). A multislice solution is implemented for a paraxial version of the Pauli equation. Simulations require the magnetic fields in the sample as input. A realistic description of magnetism in a solid, for this purpose, is derived in a scheme starting from a DFT calculation of the spin density or density matrix. Calculations are performed for electron vortex beams passing through magnetic solids and a magnetic signal, defined as a difference in intensity for opposite orbital angular momentum beams, integrated over a disk in the diffraction plane, is observed. For nanometer sized electron vortex beams carrying orbital angular momentum of a few tens of ħ, a relative magnetic signal of order 10-3 is found. This is considered realistic to be observed in experiments. In addition to electron vortex beams, spin polarised and phase aberrated electron beams are considered and also for these a magnetic signal, albeit weaker than that of the vortex beams, can be obtained.Felaktigt ISBN i den tryckta versionen: 9789155497149
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Menshawy, Samh. "Réponse dynamique d’un nano-oscillateur spintronique à un signal rf pour le développement de nouveaux détecteurs rf ultra-miniatures." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS076/document.
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Les nano-oscillateurs spintroniques présentent des propriétés remarquables en termes de détection radiofréquence. Leurs tailles nanométriques, leur fonctionnement à température ambiante et leurs compatibilité CMOS en font des candidats sérieux pour apporter la fonction d’analyse spectrale instantanée dans des systèmes embarqués. Les travaux de cette thèse portent sur les propriétés de détection des STNOs à base de vortex magnétiques. Un des effets conférant aux STNOs la possibilité de détecter un signal rf est l’effet diode de spin. Une source rf permet de créer le signal à détecter. Lorsque la fréquence du courant rf injecté dans le STNO correspond à sa fréquence de résonance, une tension de rectification est créée à ses bornes. La mesure de cette tension par un simple voltmètre permet alors de déterminer la présence d’un courant rf. L’étude de l’évolution de la fréquence de résonance en fonction du rayon du STNO, du courant dc et du champ magnétique a mis en avant la possibilité de choisir la fréquence de résonance et de l’accorder avec ces paramètres. Dans une perspective applicative, cette propriété est essentielle pour allouer un STNO à une fréquence spécifique à détecter. De plus, la taille nanométrique des STNOs permettent d’envisager un système composé d’un réseau de milliers, voire de millions de STNOs contenues sur une puce fonctionnant à température ambiante. Cependant plusieurs problématiques se posent. La sensibilité du STNOs à un signal rf extérieur doit permettre de déterminer l’état d’occupation d’un canal de fréquence par une simple mesure de la tension ou par un comparateur de tension. Cela nécessite une variation de tension de l’ordre de la dizaine de mV. L’effet diode de spin ne permettant pas d’atteindre de telle variation, un autre effet, mesuré pour la première fois à l’Unité Mixte de Physique CNRS/Thales, appelé expulsion de vortex magnétique, est étudié. Ce phénomène a lieu quand le cœur de vortex franchit les bords du STNO lors de sa dynamique induite par transfert de spin. Grâce à cet effet, l’amplitude de la variation de tension peut atteindre jusqu’à 25 mV dans les STNOs caractérisés dans le cadre de nos travaux. De plus, ce phénomène est également accordable en fréquence. Dans une perspective applicative, un réseau de STNO doit être crée afin d’allouer un STNO à une gamme de fréquence spécifique et ainsi couvrir une large bande de fréquence. La répartition du courant rf vers tous les STNOs est donc une problématique à laquelle nous avons apporté une solution. L’excitation du cœur de vortex par un champ rf nous permet en effet d’exciter un grand nombre de STNO grâce à une ligne inductive lithographiée au-dessus des STNOs. La possibilité d’expulser le cœur de vortex, dans ces conditions, a été démontré. Nous avons alors étudié la dynamique du cœur de vortex induite par un champ rf lors de l’expulsion. Ces études temporelles et fréquentielles nous ont non seulement apporté des informations sur le temps de détection d’un signal rf par le STNO mais aussi sur son aimantation dans le régime d’expulsion. De plus, l’accord en fréquence du STNO est possible même lors de l’excitation du cœur de vortex par un champ rf. Enfin, ces études nous ont permis de mettre en place, étape après étape une preuve de concept démontrant la faisabilité de la détection rf avec des nano-oscillateurs spintronique. Les différentes études du phénomène d’expulsion du cœur de vortex alliées à un travail technique de conception et de fabrication considérable a permis de converger vers une solution qui constitue un point de départ vers le développement d’un détecteur d’occupation de spectre spintronique large bande, tenant sur une puce et fonctionnant à température ambianteSpintronic nano-oscillators have remarkable properties in terms of radio frequency detection. Their nanoscale sizes, room temperature operation, and CMOS compatibility make them serious candidates for providing instantaneous spectral analysis in embedded systems. This thesis concerns the detection properties of magnetic vortex-based STNOs. One of the effects conferring on STNOs the possibility of detecting a rf signal is the spin diode effect. An rf source is used to create the signal to be detected. When the rf current frequency injected into the STNO corresponds to its resonant frequency, a rectification voltage is created at its terminals. The measurement of this voltage by a simple voltmeter makes possible to determine the rf current presence. The evolution study of the resonance frequency as a function of the STNO radius, the dc current and the magnetic field has highlighted the possibility of choosing the resonant frequency and tuning it with these parameters. From an application point of view, this property is essential for allocating an STNO to a specific frequency to be detected. Furthermore, the STNO nanometric allows us to envisage a network of thousands, even millions of STNOs contained on a chip operating at ambient temperature. However, several problems arise. The STNO sensitivity to an external rf signal must allow to determine the occupancy state of a frequency channel by a simple measurement of the voltage or with a voltage comparator. This requires a voltage variation of ten mV order. The spin diode effect doesn’t allow to achieve such variation. Another effect, measured for the first time at the Unité Mixte de Physique CNRS/Thales, called magnetic vortex expulsion, is studied. This phenomenon occurs when the vortex core crosses the STNO edges during its spin transfer induced dynamics. Thanks to this effect, the voltage amplitude variation can reach up to 25 mV in the STNOs characterized during this thesis. Moreover, this phenomenon can be tuned. From an application perspective, a network of STNOs must be created in order to allocate an STNO to a specific frequency range and thus cover a broad frequency band.The rf current distribution to all STNOs is therefore a problem to which we have brought a solution. The excitation of the vortex core by a rf field allows us to excite a large number of STNO thanks to an inductive line lithographed above the STNOs. The possibility of expelling the vortex core under these conditions has been demonstrated. We then studied the vortex core dynamics induced by an rf field during the expulsion. A time and frequency domain studies not only provided us detection time information of an rf signal by the STNO but also on its magnetization in the expulsion regime. Moreover, the STNO frequency tuning is possible even when the vortex core is excited by an rf field. Finally, these studies enabled us to implement step by step a proof of concept demonstrating the rf detection feasibility with spintronic nano-oscillators. The various studies of vortex core expulsion combined with a considerable technical work of design and manufacture finally allowed us to converge towards a solution that constitutes a starting point towards the development of a broadband spintronic spectrum occupancy detector, contained on a chip and operating at room temperature
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Banholzer, Anja. "Magnetische Charakterisierung von Vortex-Dreifachlagen mittels Röntgentransmissionsmikroskopie, Magnetowiderstand und ferromagnetischer Resonanz." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-193802.
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In dieser Arbeit werden magnetische Vortex-Dreifachlagen-Systeme untersucht. Mittels Magnetfeld, Strom und Röntgenzirkulardichroismus kann erstmals die magnetische Konfiguration der Vortexlagen mit dem simultan gemessenen Magnetowiderstand verglichen werden. Die senkrecht mit Strom durchflossenen Kobalt-Kupfer-Permalloy Scheiben werden in einem Mehrschrittprozess mittels Elektronenstrahllithographie auf einer Membran hergestellt, um mit Rastertransmissions-Röntgenmikroskopie untersuchbar zu sein. Die Auswertung der STXM-Bilder zeigt das gleiche Verhalten wie die Widerstandsmessungen und erlaubt eine eindeutige Zuordnung.
Um auch die kleinsten scheibenförmigen Dreifachlagensysteme mittels ferromagnetischer Resonanz zu messen, wurde die Mikroresonator FMR optimiert. Damit können bereits etwa 2.3*10^7 Kobaltatome gemessen werden, wobei die Empfindlichkeit bis zu 4*10^6 Atomen ausreichend sein sollte. Durch 6-fache Mittelung lässt sich ein Kobaltwürfel mit einer Kantenlänge von 12,5nm detektieren. Dabei sind nicht nur die uniforme Mode, sondern auch lokal angeregte Moden sichtbar. Mittels mikromagnetischer Simulationen lassen sich den Resonanzen Modenbilder zuordnen. Die scheibenförmige Dreifachlage wird mit den FMR-Messungen sowohl mit verringertem Durchmesser, als auch mit reduzierter Zwischenschicht untersucht.
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Rouco, Gómez Víctor. "Controlling Vortex Pinning and Dynamics of Nanostructured YBCO Thin Films Grown by Chemical Solution Deposition." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/133329.
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Desde el descubrimiento de los Superconductores de Alta Temperatura (SCAT), se ha realizado un gran esfuerzo con tal de optimizar las propiedades eléctricas de estos materiales. A diferencia de los Superconductores convencionales de Baja Temperatura (SCBT), algunos de los SCAT son capaces de alcanzar el estado superconductor a la temperatura de ebullición del nitrógeno (77K) haciéndolos mucho más atractivos en cuanto a aplicaciones tecnológicas dados los reducidos costes de operación.
Una de las principales aplicaciones de los SCAT es el transporte eléctrico. La ausencia de resistencia eléctrica de estos materiales cuando están por debajo de su temperatura crítica, Tc, hacen que puedan transportar hasta 10 veces más de potencia que los cables convencionales, o proporcionar una misma potencia con niveles muy inferiores de voltaje.
Por otro lado, los SCAT han sido profundamente estudiados en el ámbito de la electrónica. En particular, nanohilos de SCAT pueden ser escalados a tamaños menores debido a sus pequeñas longitudes intrínsecas. Además, sus rápidos coeficientes de relajación permiten altos niveles de adquisición en experimentos de fotodetección cuando éstos son comparados con SCBT.
No obstante, una de las características más importantes en el estudio de los SCAT es la presencia de líneas de flujo magnético cuantificadas, denominadas vórtices, en su diagrama de fase. Su mayor diferencia con respecto a los SCBT surge cuando se tienen en cuenta las altas excitaciones térmicas. Como consecuencia, una gran variedad de defectos de anclaje son necesarios con la finalidad de evitar (o controlar) la dinámica de los vórtices y por lo tanto, la disipación eléctrica resultante.
El control del anclaje y la dinámica de los vórtices es la finalidad de esta tesis donde los principales resultados están presentados en los capítulos 3, 4 y 5. Previamente, en el capítulo 1 presentamos las principales propiedades superconductoras y en particular, las referidas al comportamiento de los vórtices en muestras de YBa2Cu3O7-x (YBCO -superconductor con el más amplio rango de operación-) crecidas por el método de deposición de soluciones químicas (DSQ). En el capítulo 2 exponemos las técnicas experimentales utilizadas así como los procedimientos de medida.
En el capítulo 3, un gran análisis sobre el anclaje de vórtices es presentado. Un fenómeno sin precedentes en el anclaje de vórtices es demostrado el cual permite mejorar la densidad de corriente crítica y su anisotropía en presencia de fases secundarias no-superconductoras dentro de la matriz de YBCO. Además, un análisis de la dinámica de los vórtices con respecto a los defectos naturales de muestras de YBCO-DSQ es expuesto.
En los capítulos 4 y 5 nos focalizamos en el control de la dinámica de los vórtices en capas finas de YBCO. En el capítulo 4 demostramos un sentido preferencial para el movimiento de los vórtices cuando nanoestructuras asimétricas son diseñadas en la capa de YBCO. Como consecuencia, una rectificación AC-DC es obtenida.
En el capítulo 5, los estudios están centrados en la interacción entre materiales superconductores y ferromagnéticos. Se demuestra como introduciendo nanocilindros ferromagnéticos dentro de la matriz del YBCO, un enorme control sobre la densidad de corriente crítica es posible en función del estado magnético de los nanocilindros.
Las conclusiones generales están expuestas y resumidas en el último capítulo. Finalmente, el procedimiento analítico utilizado en una simulación teórica presentada en el capítulo 5 es explicado en el apéndice.Since the discovery of High-Temperature Superconductors (HTS) a huge effort has been devoted in order to optimize the electric power properties of these materials. As a difference from conventional Low-Temperature Superconductors (LTS), some HTS are able to achieve the superconducting state at the boiling point of nitrogen (77K), making these materials much more attractive for technological applications due to their reduced operating costs. One of the main applications of HTS is the electrical transport. Due to the zero electrical resistance of these materials when they are below the critical temperature, Tc, they can transmit up to 10 times more power than conventional cables or can carry equivalent power at much lower voltages. On the other hand, HTS materials have been deeply studied in the field of electronics. In particular, HTS nanowires can be functionally scaled to smaller sizes due to their extremely short intrinsic lengths. Furthermore, their characteristic fast relaxation rates offer higher counting rates in photodetection experiments when compared to LTS. However, one of the most important issues to take into account in the study of HTS, is the presence of quantified magnetic flux lines, referred as vortex, into their phase diagram. The main difference from LTS concerning the vortex behavior arises from the high thermal excitations. Consequently a great variety of different pinning centers are needed in order to avoid (or control) the vortex dynamics and therefore, the resulting electrical dissipation. Controlling vortex pinning and dynamics is the aim of this thesis where the main results are presented in chapters 3, 4 and 5. Previously, in chapter 1 we present the main superconducting properties, and in particular, the regarding to vortex behavior in YBa2Cu3O7-x (YBCO -HTS with the widest operating range-) samples grown following the Chemical Solution Deposition (CSD) technique. In chapter 2 we show the experimental techniques used in our analysis and the measurement procedure. In chapter 3, a huge analysis of vortex pinning is presented. An unprecedented phenomenon for vortex pinning is demonstrated which allows improving the critical current density and its anisotropy in the presence of non-superconducting secondary phases into the YBCO matrix. Furthermore, an analysis of the vortex dynamics with YBCO-CSD natural defects is performed. In chapters 4 and 5 we have focused in controlling vortex dynamics in YBCO thin films. In chapter 4 a preferential sense for the vortex movement is demonstrated when asymmetric nanostructures are patterned in the YBCO layer. Consequently, a controlled AC-DC rectification is obtained. In chapter 5, the studies are centered in the interaction between superconducting and ferromagnetic materials. It is demonstrated that by inserting ferromagnetic nanorods into the YBCO matrix, a huge control of the critical current density is possible as a function of the magnetic state of the nanorod. General conclusions of the thesis are presented and summarized in the last chapter. Finally, the analytical procedure used in a theoretical simulation presented in chapter 5 is exposed in the appendix.
Books on the topic "Magnetised vortex"
1
Bontemps, Nicole. The Vortex State. Dordrecht: Springer Netherlands, 1994.
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Huebener, R. P. Vortices in Unconventional Superconductors and Superfluids. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002.
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service), SpringerLink (Online, ed. Scanning SQUID Microscope for Studying Vortex Matter in Type-II Superconductors. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012.
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Allan, Poe Edgar. Tales of Science. Fairfield: 1st World Library, 2006.
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Allan, Poe Edgar. Histoires extraordinaires. Paris: Géo Ado, 2006.
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Baudelaire, Charles, and Poe Edgar Allan. Histoires extraordinaires. Paris: GF Flammarion, 1993.
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Allan, Poe Edgar. Histoires extraordinaires. Paris: Gallimard, 2005.
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Allan, Poe Edgar. Racconti del terrore. Roma: Newton Compton, 2013.
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Allan, Poe Edgar. Tales of Mystery and Imagination. New York: Gramercy Books, 1994.
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Allan, Poe Edgar. Ten Great Mysteries by Edgar Allan Poe. New York: Scholastic Inc., 1989.
Find full textBook chapters on the topic "Magnetised vortex"
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Michels, Andreas. "Magnetic Sans of Nanoparticles and Complex Systems." In Magnetic Small-Angle Neutron Scattering, 172–222. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198855170.003.0005.
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This chapter provides an overview on the magnetic SANS of nanoparticles and complex systems, which include ferrofluids, magnetic steels, and spin glasses and amorphous magnets. The underlying assumptions of the conventional particle-matrix-based model of magnetic SANS, which assumes uniformly magnetized domains, characteristic e.g., for superparamagnets, are discussed and we provide a complete specification of the micromagnetic boundary-value problem. First attempts to provide analytical expressions for the vortex-state-related magnetic SANS of thin circular discs are considered.
Conference papers on the topic "Magnetised vortex"
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Lyuksyutov, Igor F., and Valery L. Pokrovsky. "Magnetism-coupled vortex matter." In SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, edited by Ivan Bozovic and Davor Pavuna. SPIE, 1998. http://dx.doi.org/10.1117/12.332461.
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Kono, Mitsuo, Hideaki Shibahara, and Kentaro Yabuki. "Point vortex dynamics in a magnetized plasma." In U.S.-Japan workshop on ion temperature gradient-driven turbulent transport. AIP, 1994. http://dx.doi.org/10.1063/1.44523.
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TANAKA, M. Y. "PLASMA HOLE — A SINGULAR VORTEX IN A MAGNETIZED PLASMA." In Statistical Physics, High Energy, Condensed Matter and Mathematical Physics - The Conference in Honor of C. N. Yang'S 85th Birthday. WORLD SCIENTIFIC, 2008. http://dx.doi.org/10.1142/9789812794185_0081.
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Kawai, Yosuke, Yasuhito Kiwamoto, James R. Danielson, and Thomas Sunn Pedersen. "Turbulent Cascade in Vortex Dynamics of Magnetized Pure Electron Plasmas." In NON-NEUTRAL PLASMA PHYSICS VII: Workshop on Non-Neutral Plasmas 2008. AIP, 2009. http://dx.doi.org/10.1063/1.3122271.
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LAKE, B., T. E. MASON, G. AEPPLI, K. LEFMANN, N. B. CHRISTAINSON, D. F. MCMORROW, K. N. CLAUSEN, et al. "VORTEX MAGNETISM IN THE HIGH-TEMPERATURES SUPERCONDUCTOR LA2-xSRxCUO4." In Physical Phenomena at High Magnetic Fields - IV. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812777805_0062.
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Es'kin, V. A., and A. V. Kudrin. "Diffraction of an electromagnetic vortex bessel beam by the end of a semi-infinite magnetized plasma cylinder." In 2017 Progress In Electromagnetics Research Symposium - Spring (PIERS). IEEE, 2017. http://dx.doi.org/10.1109/piers.2017.8261963.
Full textReports on the topic "Magnetised vortex"
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Tajima, T., W. Horton, P. Morrison, J. Schutkeker, T. Kamimura, K. Mima, and Y. Abe. Instabilities and vortex dynamics in shear flow of magnetized plasmas. Office of Scientific and Technical Information (OSTI), March 1990. http://dx.doi.org/10.2172/7055389.
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