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Ferromagnetic Domains
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Ferromagnetic Domains ab 39.49 € als Taschenbuch: . Aus dem Bereich: Bücher, English, International, Englische Taschenbücher,

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Magnetic Domains in the Ferromagnetic Semicondu...
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Magnetic Domains in the Ferromagnetic Semiconductor (GaMn)(AsP) ab 59 € als Taschenbuch: Domain self-organization and domain wall dynamics. Aus dem Bereich: Bücher, Wissenschaft, Physik,

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Magnetic Domains in the Ferromagnetic Semicondu...
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Magnetic Domains in the Ferromagnetic Semiconductor (GaMn)(AsP) ab 59 EURO Domain self-organization and domain wall dynamics

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Superconducting Proximity Effect in Mesoscopic ...
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This book consists of two parts. In the first part, we investigate the superconducting proximity effect in a clean magnetic structure consisting of two ferromagnetic layered domains with antiparallel magnetizations in contact with a superconductor. Within the quasiclassical Green's function approach we find that the penetration of the superconducting correlations into the magnetic domains can be enhanced as compared to the corresponding single domain structure. This enhancement depends on an effective exchange field which is determined by the thicknesses and exchange fields of the two domains. In the second part, we study the superconducting proximity effect in a clean nonmagnetic metal in contact with a ferromagnetic superconductor which has a nonunitary f-wave triplet order parameter. Using the quasiclassical Green's function approach, we solve the Eilenberger equation analytically in a non-self-consistent form. The density of states is obtained in the bulk of the ferromagnetic superconductor and it is plotted versus the energy. We have compared energy-dependence of density of states with the corresponding dependences for s-wave and d-wave superconductors.

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Magnetic Domains in the Ferromagnetic Semicondu...
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GaMnAs is a model system for diluted ferromagnetic semiconductors. The origin of ferromagnetism is the exchange interaction between the carriers and the Mn 3d spins with exchange constant Jpd. The phosphorous alloying of GaMnAs is used as a novel practical technique to adjust the magnetic anisotropy. It provides layers with perpendicular anisotropy with high homogeneity. The spin-stiffness constant A is determined and the field-driven domain wall dynamics is investigated using Kerr microscopy. In GaMnAsP due to the low density of defects the magnetic domains form a self-organized pattern. From its period the spin-stiffness constant A and the first neighbor effective exchange energy JMnMn are determined. JMnMn is larger than in GaMnAs. This result along with the higher spin-wave stiffness in GaMnAsP might indicate that the Jpd value is higher in GaMnAsP than in GaMnAs. The temperature dependence of A is experimentally determined and compared to the theoretical predictions. The field-driven domain wall dynamics is studied in GaMnAsP and GaMnAs.The domain wall undergoes a flexion and twist therefore the experimental velocity curves deviate from the theoretical 1D model.

Anbieter: Dodax
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Surface Magnetism
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This book is intended to give an introduction and a comprehensive overview concerning the main areas of surface magnetism with special emphasis on rare earth metals. Investigations in this ?eld require experimental techniques which are sensitive to the topmost layers on the one hand and simultaneously to magnetic properties on the other hand. Using additionally tools with a high lateral resolution the visualization of magnetic domains becomes possible. Theunderstandingofmagneticandelectronicbehaviorrequirestheknowledgeof the structure on a microscopic scale. Due to this important relationship the dep- dence of electronic on structural properties is the ?rst topic. This contains inves- gations not only on rare earth metals but additionally on 3d ferromagnetic systems. It is important to keep in mind that the chemical behavior of a surface det- mines the surface electronic properties. Thus, variations, e.g. due to adsorbate atoms, have a signi?cant in?uence. This aspect will be focused on as the next topic with the description of selected substrate layers which were exposed to different types of gaseous molecules. Investigations on the surface magnetism of itinerant ferromagnetic materials, including the in?uence of adsorbates on surface magnetic properties, and magnets with localized moments is the ?nal and main topic of this volume. It will end with the realization of laterally resolved spin polarized vacuum tunneling which enables to image magnetic domains on the nanometer scale. Acknowledgements This work summarizes my research on the above-mentioned topics performed at the Universities of Bielefeld, Mainz, Hamburg, and Düsseldorf.

Anbieter: Dodax
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Magnetic Domains in the Ferromagnetic Semicondu...
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GaMnAs is a model system for diluted ferromagnetic semiconductors. The origin of ferromagnetism is the exchange interaction between the carriers and the Mn 3d spins with exchange constant Jpd. The phosphorous alloying of GaMnAs is used as a novel practical technique to adjust the magnetic anisotropy. It provides layers with perpendicular anisotropy with high homogeneity. The spin-stiffness constant A is determined and the field-driven domain wall dynamics is investigated using Kerr microscopy. In GaMnAsP due to the low density of defects the magnetic domains form a self-organized pattern. From its period the spin-stiffness constant A and the first neighbor effective exchange energy JMnMn are determined. JMnMn is larger than in GaMnAs. This result along with the higher spin-wave stiffness in GaMnAsP might indicate that the Jpd value is higher in GaMnAsP than in GaMnAs. The temperature dependence of A is experimentally determined and compared to the theoretical predictions. The field-driven domain wall dynamics is studied in GaMnAsP and GaMnAs.The domain wall undergoes a flexion and twist therefore the experimental velocity curves deviate from the theoretical 1D model.

Anbieter: Orell Fuessli CH
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Dynamics of magnetic vortices and antivortices ...
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Magnetic singularities in micron-sized ferromagnetic elements have been proposed for new concepts of magnetic data storage and are an ideal model system for the investigation of magnetization dynamics. This thesis deals with the dynamics of magnetic vortices as well as antivortices at picosecond and nanosecond timescales. High frequency alternating fields and spin-polarized currents are used for the manipulation of the vortices’ magnetic states. The special case of rotational excitation is investigated by time-resolved magnetic transmission x-ray microscopy, micromagnetic simulations, and analytical calculations. For magnetic antivortices we find an asymmetric response to field and current excitation that we can explain with the negative winding number of their domains. In addition, we study the dynamics of magnetic vortices in the frequency domain by means of ferromagnetic absorption spectroscopy. We find deviations from the linear dynamics that we assumed previously. These deviations are explained in the context of a nonparabolic confining potential and a critical maximum velocity of vortex motion. Absorption spectra are found to be crucially influenced by the continuous reversal of the vortex-core polarization for high amplitudes of excitation. The insight into vortex dynamics gained in this work is crucial for a successful application of vortices for data storage devices. Magnetische Singularitäten in mikroskopisch kleinen, ferromagnetischen Dünnfilmelementen könnten in der Zukunft in magnetischen Speichermedien Verwendung finden. Des Weiteren stellen sie ein ideales Modellsystem für die Untersuchung der Magnetisierungsdynamik dar. Diese Arbeit behandelt die Dynamik magnetischer Wirbel, der sogenannten Vortizes und Antivortizes, auf Zeitskalen von wenigen Pikosekunden bis zu mehreren Nanosekunden. Hochfrequente magnetische Wechselfelder und spin-polarisierte Ströme werden genutzt um die magnetischen Zustände dieser Strukturen gezielt zu verändern. Mittels zeitaufgelöster Röntgenmikroskopie, mikromagnetischer Simulationen und analytischer Berechnungen untersuchen wir den speziellen Fall einer rotierenden Anregung. Für magnetische Antivortizes erhalten wir ein asymmetrisches Verhalten bezüglich der Feld- und Stromanregung, welche auf die besondere, negative Windungszahl der Domänenstruktur zurückzuführen ist. Zusätzlich erforschen wir die Dynamik magnetischer Vortizes im Frequenzraum mittels ferromagnetischer Absorptionsspektroskopie. Hierbei finden wir Abweichungen von den zuvor entwickelten linearen Bewegungsgleichungen. Diese Abweichungen lassen sich jedoch durch die Annahme nicht-parabolischer Einschluss-Potentiale und einer kritischen maximalen Geschwindigkeit der Vortexbewegung erklären. Es stellt sich heraus, dass die gemessenen Absorptionsspektren ab einer gewissen Anregungsamplitude grundlegend durch das kontinuierliche Schalten der Vortex-Polarisation beeinflusst werden. Der Einblick, der durch die vorliegende Arbeit in die Dynamik magnetischer Wirbel gewonnen wird, ist Grundlage für eine erfolgreiche Anwendung magnetischer Vortizes als Speichermedium.

Anbieter: Orell Fuessli CH
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Nanoscale Devices - Fundamentals and Applications
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Over the last decade the interest in nanoscale materials and their applications in novel electronic devices have been increasing tremendously. This is caused by the unique properties of nanoscale materials and the outstanding performance of nanoscale devices. The fascinating and often unrivalled properties of nanoscale materials and devices opened new and sometimes unexpected fields of applications. Today, the widespread applications range from the detection of explosives, drugs and fissionable materials to bio- and infrared-sensors, spintronic devices, data storage media, magnetic read heads for computer hard disks, single-electron devices, microwave electronic devices, and many more. This book contains a collection of papers giving insight into the fundamentals and applications of nanoscale devices. The papers have been presented at the NATO Advanced Research Workshop on Nanoscale Devices - Fundamentals and Applications (NDFA-2004, ARW 980607) held in Kishinev (Chisinau), Moldova, on September 18-22, 2004. The main focus of the contributions is on the synthesis and characterization of nanoscale magnetic materials, the fundamental physics and materials aspects of solid-state nanostructures, the development of novel device concepts and design principles for nanoscale devices, as well as on applications in electronics with special emphasis on defence against the threat of terrorism. TOC:Contents. Preface.Acknowledgments. Contributing Authors. Science against nontrivial Threat. Surface Acoustic Wave Studies for Chemical and Biological Sensors.-The Experience of Utilizing the Explosives Detection System on the Basis of Neutron Radiation Analysis Together with X-Ray Units at the Airport 'Pulkovo' in St.-Petersburg.-Thermodynamic Principles of Artificial Nose Based on Supramolecular Receptors.-Molecular Detection with Magnetic Labels and Magnetoresistive Sensors.- Weak Magnetic Fields Detection Techniques and Devices. Magnetic Tunnel Junctions Based on Half-Metallic Oxides; R. Gross.-MEMS Tunable Dielectric Resonator.-Ultra-Thin Spin-Valve Structures Grown on the Surface-Reconstructed GaAs Substrate.-Novel Ideas and Principles of Devices. Negative U Molecular Quantum Dot.-Configuring a Bistable Atomic Switch by Repeated Electrochemical Cycling.-Realization of an N-Shaped IVC of Nanoscale Metallic Junctions Using the Antiferromagnetic Transition.-PI-Shift Effect and Ferromagnet/Superconductor Nanoscale Devices. Josephson Effect in Composite Junctions with Ferromagnetic Materials.- Depairing Currents in Bilayers of Nb/Pd89Ni11.-Superconductor-Ferromagnet Heterostructures.-Superconducting/Ferromagnetic Nanostructures: Spin Fluctuations and Spontaneous Supercurrents.-Coherence Effects in F/S and N/F Nanostructures. Proximity Effect and Interface Transparency in Nb-based S/N and S/F Layered Structures.-Properties of S/N Multilayers with Different Geometrical Symmetry.-Andreev Reflection in Ballistic Superconductor-Ferromagnet Contacts.- Superconductor-Insulator Transition in a PbzSn1zTe:In Solid Solution.-Advanced Sensors of Electromagnetic Radiation. Thermoelectricity of Low-Dimensional Nanostructured Materials.- Organic Semiconductors - More Efficient Material for Thermoelectric Infrared Detectors.-Submillimeter Radiation-Induced Persistent Photoconductivity in Pb1-x SnxTe(In).-Quasioptical Terahertz Spectrometer Based on a Josephson Oscillator and a Cold Electron Nanobolometer.- Novel Materials for Electronics. Origin of the Resistive Transition Broadening for Superconducting Magnesium Diboride.-Aharonov-Bohm Oscillations in Single Bi Nanowires.- Some Application of Nanocarbon Materials for Novel Devices.-Nanomaterials and Domains. Nanocrystalline Iron-Rare Earth Alloys: Exchange Interactions and Magnetic properties.-The Influence of Applied Field on the Nucleation and Growth of Heteroepitaxial Carbon Films.-

Anbieter: Orell Fuessli CH
Stand: 24.02.2020
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