Doctoral Thesis
Refine
Year of publication
- 2009 (31) (remove)
Document Type
- Doctoral Thesis (31) (remove)
Has Fulltext
- yes (31)
Is part of the Bibliography
- no (31)
Keywords
- Theoretische Physik (3)
- Quark-Gluon-Plasma (2)
- Relativistische Hydrodynamik (2)
- Schwerionenstoß (2)
- Strahldynamik (2)
- relativistic hydrodynamics (2)
- ATR-Spektroskopie (1)
- Abstandsinformation (1)
- Akupunktur (1)
- Akustik (1)
- Angewandte Physik (1)
- BEDT-TTF (1)
- Beam dynamics (1)
- Beamforming (1)
- Beliaev Dämpfung (1)
- Beliaev damping (1)
- BetP (1)
- Betain (1)
- Biophysik (1)
- Bleikern (1)
- Boltzmann-Gleichung (1)
- Breitbandigkeit (1)
- Broadband (1)
- CERN (1)
- CERN SPS (1)
- Chiral Symmetry (1)
- Chirale Symmetrie (1)
- Cluster (1)
- Correlations (1)
- DNA Translocation (1)
- Dielectric Boundaries (1)
- Differential Arrays (1)
- Dileptonen (1)
- Dileptons (1)
- Dünne Schicht (1)
- Elementarteilchenphysik (1)
- Ensemble Inequivalance (1)
- Erbrechen (1)
- FT-IR-Spectroscopy (1)
- FT-IR-Spektroskopie (1)
- Festkörperphysik (1)
- Fluctuation (1)
- Fluctuations (1)
- Fluktuation <Physik> (1)
- Fractional Delay Filters (1)
- Fractional-Delay-Filter (1)
- Functional Renormalization Group (1)
- Funktionale Renormierungsgruppe (1)
- Funktionelle NMR-Tomographie (1)
- Größenkonstanzleistung (1)
- H/D Austausch (1)
- Hadron (1)
- Heavy Ion Collisions (1)
- Hirnstamm (1)
- Infrarotspektroskopie (1)
- Jet-Medium-Wechselwirkungen (1)
- Kaon (1)
- Kern-Kern-Streuung (1)
- Kern-Kern-Stößen (1)
- Kernphysik (1)
- Korrelation (1)
- Kraftmikroskopie (1)
- Ladungstransfer (1)
- Mach cone (1)
- Machkegel (1)
- Membraneproteins (1)
- Membranproteine (1)
- Microphones (1)
- Mikrofone (1)
- Modal Subspace Decomposition (1)
- Modale Subraum-Zerlegung (1)
- Mondphänomen (1)
- Mondtäuschung (1)
- Monte-Carlo-Simulation (1)
- Moonillusion (1)
- Multiplizität (1)
- Multipole (1)
- Multipoles (1)
- NMR-Tomographie (1)
- Nausea (1)
- Nepomnyashchy theorem (1)
- Neurophysiologie (1)
- Neutron Star (1)
- Neutronenstern (1)
- Nucleus dorsalis nervi vagi (1)
- Nucleus-Nucleus Collisions (1)
- OmpF (1)
- OmpG (1)
- Osmosensor (1)
- Phase transition (1)
- Phasenumwandlung (1)
- Photoionisation (1)
- Photoionization (1)
- Physik (1)
- Pion (1)
- Poisson-Gleichung (1)
- Porin (1)
- Protein-Lipid Wechselwirkung (1)
- Proteorhodopsin (1)
- Psychophysik (1)
- Quark <Physik> (1)
- Quark deconfinement (1)
- Quarkconfinement (1)
- Renormierungsgruppe (1)
- Resonances (1)
- Resonanzen (1)
- Ribulosebisphosphat-Carboxylase (1)
- Rückstoßimpulsspektroskopie (1)
- Satz von Nepomnyashchy (1)
- Schwerionenkollisionen (1)
- Secondary Structure (1)
- Sekundärstruktur (1)
- Sensor-Array (1)
- Speicherring (1)
- Statistische Mechanik (1)
- Storage ring (1)
- Superdirectivity (1)
- Superdirektivität (1)
- Symmetriebrechung (1)
- Teilchen (1)
- Teilchenbeschleuniger (1)
- Teilchenerzeugung (1)
- Temperaturbeständigkeit (1)
- Theoretical physics (1)
- Thermal Stability (1)
- Thermodynamische Eigenschaft (1)
- Toroidal magnetic field (1)
- Toroidalen Magnetfeld (1)
- Transport Approach (1)
- Transportmodellen (1)
- Vagus (1)
- Vakuumdeposition (1)
- Vegetatives Nervensystem (1)
- Wahrnehmungsgröße (1)
- Weiche Materie (1)
- beam dynamics (1)
- carboxylation (1)
- constant of size (1)
- critical systems (1)
- default mode network (1)
- differentielle Arrays (1)
- distance information (1)
- fixed effects analysis (1)
- hadronic transport approach (1)
- heavy ion collisions (1)
- heavy-ion collision (1)
- hybrid approach (1)
- infrared spectroscopy (1)
- interacting bosons (1)
- jet-medium interactions (1)
- kritische Systeme (1)
- laserakupunktur (1)
- methodenkritik (1)
- monte carlo simulation (1)
- nuclear physics (1)
- particle accelerators (1)
- photocycle (1)
- proteorhodopsin (1)
- quark-gluon plasma (1)
- random effects analysis (1)
- recoil ion momentum spectroscopy (1)
- resting state (1)
- rubisco (1)
- thin film (1)
- vacuum deposition (1)
- visual perceptional size (1)
- wechselwirkende Bosonen (1)
Institute
- Physik (31) (remove)
The characterization of microscopic properties in correlated low-dimensional materials is a challenging problem due to the effects of dimensionality and the interplay between the many different lattice and electronic degrees of freedom. Competition between these factors gives rise to interesting and exotic magnetic phenomena. An understanding of how these phenomena are driven by these degrees of freedom can be used for rational design of new materials, to control and manipulate these degrees of freedom in order to obtain desired properties. In this work, we study these effects in materials with small exchange interaction between the magnetic ions such as metal-organic and inorganic dilute compounds. We overcome the dfficulties in studying these kind of materials by combining classical and quantum mechanical ab initio methods and many-body theory methods in an effective theoretical approach. To treat metal-organic compounds we elaborate a novel two-step methodology which allows one to include quantum effects while reducing the computational cost. We show that our approach is an effective procedure, leading at each step, to additional insights into the essential features of the phenomena and materials under study. Our investigation is divided into two parts, the first one concerning the exploration of the fundamental physical properties of novel Cu(II) hydroquinone-based compounds. We have studied two representatives of this family, a polymeric system Cu(II)-2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene (CuCCP) and a coupled system Cu2S2F6N8O12 (TK91). The second part concerns the study of magnetic phenomena associated with the interplay between different energy scales and dimensionality in zero-, one- and two-dimensional compounds. In the zero-dimensional case, we have performed a comprehensive study of Cu4OCl6L4 with L=diallylcyanamide=NC-N-(CH2-CH=CH2)2 (Cu4OCl6daca4). Interpretations of the magnetic properties for this tetrameric compound have been controversial and inconsistent. From our studies, we conclude that the common models usually applied to this and other representatives in the same family of cluster systems fail to provide a consistent description of their low temperature magnetic properties and we thus postulate that in such systems it is necessary to take into account quantum fluctuations due to possible frustrated behavior. In the one-dimensional case, we studied polymeric Fe(II)-triazole compounds, which are of special relevance due to the possibility of inducing a spin transition between low and high spin state by applying a external perturbation. A long standing problem has been a satisfactory microscopic explanation of this large cooperative phenomenon. A lack of X-ray data has been one mitigating reason for the absence of microscopic studies. In this work, we present a novel approach to the understanding of the microscopic mechanism of spin crossover in such systems and show that in these kind of compounds magnetic exchange between high spin Fe(II) centers plays an important role. The correct description of the underlying physics in many materials is often hindered by the presence of anisotropies. To illustrate this difficulty, we have studied a two dimensional dilute compound K2V3O8 which exhibits an unusual spin reorientation effect when applying magnetic fields. While this effect can be understood when considering anisotropies in the system, it is not sufficient to reproduce experimental observations. Based on our studies of the electronic and magnetic properties in this system, we predict an extra exchange interaction and the presence of an additional magnetic moment at the non-magnetic V site. This sheds a new light into the controversial recent experimental data for the magnetic properties of this material.