Synthese, der Kristallzucht und der Untersuchung der Schichtkobaltate RBaCo2O5+δ.

This thesis is concerned with synthesis, crystal growth and investigation of layered cobaltites compounds RBaCo2O5+δ. The properties investigated in this work are related to the macroscopic ones as well as quantities determined using local probes. The main techniques used are: travelling floating zone for the crystal growth, muon spin rotation, neutron and synchrotron radiation diffraction measurements as well as complementary techniques like: X-ray diffraction, bulk magnetization and transport measurements. Based on the obtained experimental data, a magnetic model is proposed below the paramagnetic phase as well as the driving force for the apparition of metal-insulator transition in the paramagnetic phase. The results presented in this thesis hopefully add to the rapidly growing understanding of this family of compounds. The results are certainly not directly applicable to the industry today, but they give a new interpretation of some of the new exciting phenomena and properties which characterize these systems.Diese Doktorarbeit befasst sich mit der Synthese, der Kristallzucht und der Untersuchung der Schichtkobaltate RBaCo2O5+δ. Die hier untersuchten Eigenschaften sind solche makroskopischer Art sowie über lokale Sondenmethoden bestimmte. Die wesentlichen benutzten Techniken sind: Zonenschmelzverfahren für die Kristallzucht, Myonen Spin Rotation, Neutronen und Synchrotronstrahlungsstreuexperimente sowie dazu komplementäre Techniken wie Röntgenbeugung, Magnetisierungs und Transportmessungen. Auf der Grundlage dieser experimentellen Daten wird ein magnetisches Modell für den Temperaturbereich unterhalb der paramagnetischen Phase vorgeschlagen sowie für die treibende Kraft für den Metall-Isolator Übergang in der paramagnetischen Phase. Es wird erhofft, dass die in dieser Arbeit dargelegten Ergebnisse zu dem rasch wachsenden Verständnis dieser Verbindungsfamilie beitragen. Die Ergebnisse sind zwar sicher nicht direkt für industrielle Anwendung geeignet, doch erlauben sie eine neue Interpretation einiger neuer aufregender Phänomene und Eigenschaften, die diese Systeme charakterisieren

Characteristic length scales of the secondary relaxations in glass-forming glycerol

We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends on the time scale of the relaxation of interest. We use neutron backscattering to identify the characteristic length scale of 0.7 Å for the faster secondary relaxation described in the framework of the mode-coupling theory (MCT). Neutron spin-echo is employed to probe the slower secondary relaxation of the excess wing type at a low temperature ( ∼ 1.13Tg . The characteristic length scale for this excess wing dynamics is approximately 4.7 Å. Besides the Q -dependence, the direct coupling of neutron scattering signal to density fluctuation makes this technique indispensable for measuring the length scale of the microscopic relaxation dynamics

Microscopic Evidence of Spin State Order and Spin State Phase Separation in Layered Cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho

We report muon spin relaxation measurements on the magnetic structures of RBaCo_2O_5.5 with R=Y, Tb, Dy, and Ho. Three different phases, one ferrimagnetic and two antiferromagnetic, are identified below 300 K. They consist of different ordered spin state arrangements of high-, intermediate-, and low-spin Co^3+ of CoO_6 octahedra. Phase separation into well separated regions with different spin state order is observed in the antiferromagnetic phases. The unusual strongly anisotropic magnetoresistance and its onset at the FM-AFM phase boundary is explained.Comment: 4 pages, accepted for publication in Phys. Rev. Let

Correlated decay of triplet excitations in the Shastry-Sutherland compound SrCu2_2(BO3_3)2_2

The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu$_2$(BO$_3$)$_2$ is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature while the integrated spectral weight can be explained by an isolated dimer model up to 10~K. Analyzing this anomalous spectral line-shape in terms of damped harmonic oscillators shows that the observed damping is due to a two-component process: one component remains sharp and resolution limited while the second broadens. We explain the underlying mechanism through a simple yet quantitatively accurate model of correlated decay of triplons: an excited triplon is long-lived if no thermally populated triplons are near-by but decays quickly if there are. The phenomenon is a direct consequence of frustration induced triplon localization in the Shastry--Sutherland lattice.Comment: 5 pages, 4 figure

The development of intangible assets through the cohesion policy

Intangible assets in general and intellectual capital in particular are important to both society and organizations. It can be a source of competitive advantage for business and stimulate innovation that leads to wealth generation. Technological revolutions, the rise of the knowledge-based economy and the networked society have all led to the same conclusion that intangibles and how they contribute to value creation have to be appreciated so that the appropriate decisions can be made to protect and enhance them. The Cohesion Policy represents the main EU measure to ensure a balanced and sustainable growth in Europe by promoting harmonious development and reducing the regional disparities. The general objective of the paper is to highlight the important role of the Cohesion Policy in the development of intangible assets. The objectives and the instruments of the Cohesion Policy are designed to support programs on regional development, economic change, enhanced competitiveness and territorial cooperation through the European Union, to develop human resources and employability. The article also attempts to outline the trends of the Cohesion policy for the future by presenting a series of measures suggested by the European Commission through the Europe 2020 Strategy in order to develop intangible assets

Excess wing in glass-forming glycerol and LiCl-glycerol mixtures detected by neutron scattering

The relaxational dynamics in glass-forming glycerol and glycerol mixed with LiCl is in-vestigated using different neutron scattering techniques. The performed neutron spin-echo experiments, which extend up to relatively long relaxation-time scales of the order of 10 ns, should allow for the detection of contributions from the so-called excess wing. This phenomenon, whose microscopic origin is controversially discussed, arises in a variety of glass formers and, until now, was almost exclusively investigated by dielectric spectros-copy and light scattering. Here we show that the relaxational process causing the excess wing also can be detected by neutron scattering, which directly couples to density fluctua-tions.Comment: 8 pages, 6 figure

The development of intangible assets through the cohesion policy

Intangible assets in general and intellectual capital in particular are important to both society and organizations. It can be a source of competitive advantage for business and stimulate innovation that leads to wealth generation. Technological revolutions, the rise of the knowledge-based economy and the networked society have all led to the same conclusion that intangibles and how they contribute to value creation have to be appreciated so that the appropriate decisions can be made to protect and enhance them. The Cohesion Policy represents the main EU measure to ensure a balanced and sustainable growth in Europe by promoting harmonious development and reducing the regional disparities. The general objective of the paper is to highlight the important role of the Cohesion Policy in the development of intangible assets. The objectives and the instruments of the Cohesion Policy are designed to support programs on regional development, economic change, enhanced competitiveness and territorial cooperation through the European Union, to develop human resources and employability. The article also attempts to outline the trends of the Cohesion policy for the future by presenting a series of measures suggested by the European Commission through the Europe 2020 Strategy in order to develop intangible assets