Dissertations / 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.
Full textCass, 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.
Full textMartin, 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.
Full textKayali, Mohammad Amin. "Spontaneous vortex phase and pinning in ferromagnetic-superconducting systems." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/409.
Full textMejia-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.
Full textMaster of Science
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.
Full textQC 20101209
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.
Full textFelaktigt ISBN i den tryckta versionen: 9789155497149
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.
Full textSpintronic 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
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.
Full textRouco, 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.
Full textSince 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.
Elias, Ricardo. "Solitons magnétiques et transitions topologiques." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4712/document.
Full textIn this thesis we study the magnetic solitons and its topological transitions, both theoretically and numerically. In the first part, we find a particular configuration of what is denominated the Bloch Point, a three-dimensional solution of the Free Energy minimization with exchange, Landau and dipolar terms. Oscillations around the Bloch point are found and quantized in order to understand the role of quantum fluctuations over its stability.In the second part, we look at the evolution of a system coupling ferromagnetic textures with nontrivial topology, with itinerant electrons. The interaction between the magnetic texture and the electrons is understood by means of spin-torque phenomena. This physical system is modeled with the equation Landau-Lifshitz-Gilbert equation coupled with Schrödinger equation for quantum electrons. Topological transitions are observed and understood in a general framework that unifies older works done in a more classical context. Among the large amount of topological transitions observed, we can distinguish the different roles played by electrons depending on parameters. The orders of magnitude of time and space in the topological transition events show the importance of quantum effects as well as the fundamental role of discretization
Petrişor, Traian. "Structures magnétiques modulés pour le pinning magnétique dans les supraconducteurs à haute température." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10086/document.
Full textThe present thesis deals with the fabrication and study of hybrid, ferromagnetic/superconducting, interface systems. Magnetic mezoscopic systems, whose magnetic properties were modulated by the dimensionality (thickness and lateral size) of the systems was studied. Two types of structures were considered. The first consisted of perovskite-like epitaxial LaSrMnO thin films. We have demonstrated the direct correlation between oxygen incorporation in the LaSrMnO lattice and the evolution of its structural, magnetic and electric properties. A second class of magnetic materials that has been studied consisted of transition metals (Co) and alloys (Ni80Fe20). We have defined micronic objects from the as-deposited films, by means of optical lithography and ion beam etching. These structures were then integrated to form an interface with thin epitaxial high Tc superconducting films: YBaCuO. The ultimate goal of the above studies was the control of vortex dynamics within the superconducting layer by two mechanisms: the first, intrinsic, in which flux pinning is achieved by structural defects within the superconducting film, and a second one, extrinsic, correlated with influence of the magnetic field modulations created by the adjacent mezoscopic magnetic structure
Ray, Soumya Jyoti. "Nanoscale investigation of superconductivity and magnetism using neutrons and muons." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3190.
Full textBurgos, Parra Erick Omar. "Time resolved and time average imaging of magnetic nano-structures." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34251.
Full textHamadeh, Abbass. "Synchronization of spin trasnsfer nano-oscillators." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112262/document.
Full textSpin transfer nano-Oscillators (STNOs) are nanoscale devices capable of generating high frequency microwave signals through spin momentum transfer. Although they offer decisive advantages compared to existing technology (spectral agility, integrability, etc.), their emitted power and spectral purity are quite poor. In view of their applications, a promising strategy to improve the coherence and increase the emitted microwave power of these devices is to mutually synchronize several of them. A first step is to understand the synchronization of a single STNO to an external source. For this, we have studied a circular nanopillar of diameter 200~nm patterned from a Cu60|Py15|Cu10|Py4|Au25 stack, where thicknesses are in nm. In the saturated state (bias magnetic field > 0.8 T), we have identified the auto-Oscillating mode and its coupling to an external source by using a magnetic resonance force microscope (MRFM). Only the uniform microwave field applied perpendicularly to the bias field is efficient to synchronize the STNO because it shares the spatial symmetry of the auto-Oscillation mode, in contrast to the microwave current passing through the device. The same sample was then studied under low perpendicular magnetic field, with the two magnetic layers in the vortex state. In this case, it is possible to excite a highly coherent mode (F/∆F>15000) with a linewidth below 100 kHz. By analyzing the harmonic content of the spectrum, we have determined that the non-Linear amplitude-Phase coupling of the excited mode is almost vanishing, which explains the high spectral purity observed. Moreover, the oscillation frequency can still be widely tuned thanks to the Oersted field created by the dc current. We have also shown that the synchronization of this mode to a microwave field source is very robust, the generation linewidth decreasing by more than five orders of magnitude compared to the autonomous regime. From these findings we conclude that the magneto-Dipolar interaction is promising to achieve mutual coupling of vortex based STNOs, the dipolar field from a neighboring oscillator playing the role of the microwave source. We have thus experimentally measured a system composed of two STNOs laterally separated by 100 nm. By varying the different configurations of vortex polarities, we have observed the mutual synchronization of these two oscillators
Vaňatka, Marek. "Statické a dynamické vlastnosti nanostrukturovaných magnetických materiálů." Doctoral thesis, Vysoké učení technické v Brně. CEITEC VUT, 2021. http://www.nusl.cz/ntk/nusl-438773.
Full textMeglicki, Zdzislaw. "Analysis and Applications of Smoothed Particle Magnetohydrodynamics." Phd thesis, 1995. http://hdl.handle.net/1885/49346.
Full textBanholzer, Anja. "Magnetische Charakterisierung von Vortex-Dreifachlagen mittels Röntgentransmissionsmikroskopie, Magnetowiderstand und ferromagnetischer Resonanz." Doctoral thesis, 2015. https://tud.qucosa.de/id/qucosa%3A28139.
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