1,228 research outputs found
Industrielle Realisierung von TMR-Elementen
No full textGerken A. Realization of TMR devices in an industrial environment. Bielefeld (Germany): Bielefeld University; 2010.Magnetoresistive sensors are widely used in sensor applications for magnetic field measurements. Currently these sensors mostly use the Anisotropic Magnetoresistive Effect (AMR) or the Giant Magnetoresistive Effect (GMR). Due to their unique properties sensors based on the TMR effect could be advantageous: They offer a higher MR-ratio, smaller lateral dimensions and a higher resistance which reduces the power consumption.
The work presented here is a purely industrial work, i.e. all experiments were performed directly on production tools at Sensitec GmbH in Mainz. In contrast to university research the focus was shifted to reproducibility and wafer uniformity instead of creating single perfect samples.
In this thesis a TMR layer stack consisting of sputtered CoFeB electrodes, one of them being exchange-coupled with IrMn, and an ion beam deposited MgO barrier is presented. This system was studied by many research groups and is now transferred to an industrial environment. In contrast to most publications, the MgO barrier is being prepared by ion beam deposition, a novel preparation method for TMR stacks.
Additionally Co2MnSi films for the use as potential electrodes were prepared by ion beam deposition and characterized structurally and magnetically
Ausbreitung von Jets und Entstehung von Machkegeln in (3+1) dimensionaler idealer Hydrodynamik
No full textThis thesis investigates the jet-medium interactions in a Quark-Gluon Plasma using a hydrodynamical model. Such a Quark-Gluon Plasma represents a very early stage of our universe and is assumed to be created in heavy-ion collisions. Its properties are subject of current research. Since the comparison of measured data to model calculations suggests that the Quark-Gluon Plasma behaves like a nearly perfect liquid, the medium created in a heavy-ion collision can be described applying hydrodynamical simulations. One of the crucial questions in this context is if highly energetic particles (so-called jets), which are produced at the beginning of the collision and traverse the formed medium, may lead to the creation of a Mach cone. Such a Mach cone is always expected to develop if a jet moves with a velocity larger than the speed of sound relative to the medium. In that case, the measured angular particle distributions are supposed to exhibit a characteristic structure allowing for direct conclusions about the Equation of State and in particular about the speed of sound of the medium. Several different scenarios of jet energy loss are examined (the exact form of which is not known from first principles) and different mechanisms of energy and momentum loss are analyzed, ranging from weak interactions (based on calculations from perturbative Quantum Chromodynamics, pQCD) to strong interactions (formulated using the Anti-de-Sitter/Conformal Field Theory Correspondence, AdS/CFT). Though they result in different angular particle correlations which could in principle allow to distinguish the underlying processes (if it becomes possible to analyze single-jet events), it is shown that the characteristic structure observed in experimental data can be obtained due to the different contributions of several possible jet trajectories through an expanding medium. Such a structure cannot directly be connected to the Equation of State. In this context, the impact of a strong flow created behind the jet is examined which is common to almost all jet deposition scenarios. Besides that, the transport equations for dissipative hydrodynamics are discussed which are fundamental for any numerical computation of viscous effects in a Quark-Gluon Plasma.Diese Arbeit untersucht Jet-Medium-Wechselwirkungen in einem Quark-Gluon-Plasma mittels eines hydrodynamischen Modells. Ein solches Quark-Gluon-Plasma repräsentiert eine Frühphase unseres Universums und kann in Schwerionenkollisionen erzeugt werden. Seine Eigenschaften sind Gegenstand der aktuellen Forschung. Da der Vergleich von Meßdaten und Modellrechnungen nahelegt, dass sich das Quark-Gluon-Plasma wie eine nahezu ideale Flüssigkeit verhält, läßt sich das bei einer Schwerionenkollision gebildete Medium mittels hydrodynamischer Simulationen beschreiben. Eine der in diesem Zusammenhang grundlegenden Fragestellungen ist, ob energiereiche Teilchen (sogenannte Jets), die zu Beginn einer Kollision erzeugt werden und das Medium durchqueren, zur Bildung eines Machkegels führen. Dieser kann theoretisch immer erwartet werden, wenn sich ein Jet mit Überschallgeschwindigkeit relativ zum Medium bewegt. Die gemessene Winkelverteilung der aus der Kollision hervorgehenden und in den Detektoren gemessenen Teilchen sollte dann eine charakteristische Struktur aufweisen, aus der man auf direktem Wege Rückschlüsse auf die Zustandsgleichung des Mediums, im Besonderen auf seine Schallgeschwindigkeit, ziehen kann. Es werden unterschiedliche Szenarien eines Jetenergieverlustes betrachtet, dessen exakte Form und der ihm zugrundeliegenden Wechselwirkungen unbekannt sind. Dazu werden verschiedene Quellterme untersucht, die eine solche Wechselwirkung des Jets mit dem Medium repräsentieren und die Abgabe von Energie und Impuls an das Medium beschreiben. Dabei werden sowohl Mechanismen einer schwachen Wechselwirkung (basierend auf Rechnungen der perturbativen Quantenchromodynamik, pQCD) als auch einer starken Wechselwirkung (welche anhand der sogenannten "Anti-de-Sitter/Conformal Field Theory''-Korrespondenz, AdS/CFT, ermittelt wird) behandelt. Obwohl diese in unterschiedlichen Winkelverteilungen resultieren und somit (für Einzeljetereignisse) eine Unterscheidung der zugrundeliegenden Prozesse ermöglichen könnten, zeigt sich, dass die für die gemessenen Teilchenspektren charakteristische Struktur durch die Überlagerung verschiedener Jettrajektorien beschrieben werden kann. Eine solche Struktur lässt sich nicht direkt mit der Zustandsgleichung in Verbindung bringen. In diesem Zusammenhang werden die Auswirkungen eines starken Flusses diskutiert, der sich bei nahezu allen betrachteten Jetenergieverlustszenarien entlang der Trajektorie des Jets bildet. Darüber hinaus werden die Transportgleichungen der dissipativen Hydrodynamik diskutiert, welche die Grundlage einer numerischen Berechung von viskosen Effekten innerhalb eines Quark-Gluon-Plasmas bilden
80th Annual Meeting of the DPG and DPG-Frühjahrstagung (Spring Meeting) of the Condensed Matter Section (SKM) together with the Divisions Environmental Physics, Microprobes, and Working Groups Energy, Equal Opportunities, Industry and Business, Information, Physics and Disarmament, young DPG : March 6-11, 2016, University of Regensburg
No full textEstimation of statistical moments for single point measurements in the Scrape Off Layer
No full textPoster presented at the 78th Annual Meeting of the DPG and DPG Spring Meeting, German Physical Society (DPG)
Predicting volatile wind energy: Stochastic forward modeling and machine learning
No full textPoster presented at the 86. Annual Meeting of DPG and DPG-Frühjahrstagung (DPG Spring Meeting) of the Matter and Cosmos Section (SMuK) - Dresden, Germany - 20.03. - 24.03.202
DPG-Fruehjahrstagung ASDEX contributions to the DPG Fruehjahrstagung
No full textSIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Characterization and investigation of Fe:STO thin films prepared by pulsed laser deposition
No full textAdhesive wear mechanisms in the presence of weak interfaces
No full textDespite the relevance of wear in many engineering applications, our understanding of the connection between mechanisms at the nanoscale and the observed wear rates of contacting parts at the macroscale remains limited. Recent work in our group has therefore focused on physics-based models of adhesive wear mechanisms, identifying a material-dependent critical length scale for wear particle formation. Upscaling of these findings, though, still remains challenging. One problem is that only strong adhesive bonds between contacting solids were considered. In the present contribution, we therefore extent this framework to include weaker interfaces, which are expected at typical contacts due to lattice mismatch, surface passivation, or lubrication. We use atomistic simulations on an amorphous model material to propose a mechanism map based on material properties and local contact geometry for wear particle formation and surface damage at the single-asperity scale. Our results imply that the local slopes of rough surfaces govern a transition from asperity collisions with plastic damage and wear particle formation at high roughness to slip without significant damage for flatter surfaces, comparable to a run-in process.LSM
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