The phenomenon of superconductivity - after its discovery in metals such as mercury, lead, zinc, etc. by Kamerlingh-Onnes in 19]] - has attracted many scientists. Superconductivity was described in a very satisfactory manner by the model proposed by Bardeen, Cooper and Schrieffer, and by the extensions proposed by Abrikosov, Gorkov and Eliashberg. Relations were established between superconductivity and the fundamental properties of solids, resulting in a possible upper limit of the critical temperature at about 23 K. The breakthrough that revolutionized the field was made in 1986 by Bednorz and Muller with the discovery of high-temperature superconductivity in layered copper-oxide perovskites. Today the record in transition temperature is 133 K for a Hg based cuprate system. The last decade has not only seen a revolution in the size of the critical temperature, but also in the myriads of research groups that entered the field. In addition, high-temperature superconductivity became a real interdisciplinary topic and brought together physicists, chemists and materials scientists who started to investigate the new compounds with almost all the available experimental techniques and theoretical methods. As a consequence we have witnessed an avalanche of publications which has never occurred in any field of science so far and which makes it difficult for the individual to be thoroughly informed about the relevant results and trends. Neutron scattering has outstanding properties in the elucidation of the basic properties of high-temperature superconductors.

Inhalt
to Neutron Scattering.- 1. Introduction.- 2. Properties of the neutron.- 3. Neutron scattering cross section.- 4. Coherent and incoherent scattering.- 5. Magnetic scattering.- 6. Polarization analysis.- 7. Instrumental aspects.- 8. Examples.- 9. Conclusions.- References.- Structural Anomalies, Oxygen Ordering and Superconductivity in YBa2Cu3O6+x.- 1. Introduction.- 2. Structure determination.- 3. Structural properties as a function of oxygen content.- 4. The x-T phase diagram.- 5. Quenching and ageing effects at room temperature.- 6. Local structural effects in oxygen-rich YBa2Cu3O6+x (x?1).- 7. Substituted compounds.- 8. Hole count, and phase separation: Overdoping and pressure effects.- Acknowledgements.- References.- Phase Diagrams and Spin Correlations in YBa2Cu3O6+x.- 1. The temperature-concentration phase diagram.- 2. The insulating phases.- 3. Magnetic fluctuations in the metallic state.- 4. Impurity effects: YBa2(Cu1-yZny)3O6+x.- 5. Discussion and conclusion.- Acknowledgments.- References.- Magnetic Excitations in La2-x(Ba,Sr)xCuO4.- 1. Introduction.- 2. The insulating antiferromagnet, La2CuO4.- 3. The normal metal.- 4. The superconducting metal.- Phonon Dispersions and Phonon Density-Of-States in Copper-Oxide Superconductors.- 1. Introduction.- 2. T-phase compounds.- 3. T'-phase compounds.- 4. 123-compounds.- 5. Bi-based compounds.- 6. Tl-based compounds.- 7. Hg-based compounds.- 8. Conclusive remarks.- References.- Phase Separation, Charge Segregation, and Superconductivity in Layered Cuprates.- 1. Introduction.- 2. Phase separation in La2CuO4+?.- 3. Charge segragation within the CuO2 planes.- 4. Concluding remarks.- Acknowledgments.- References.- Magnetic 2-D and 3-D Ordering Phenomena in Rare-Earth Based Copper-Oxide Superconductors andRelated Systems.- 1. Introduction.- 2. Crystal structure aspects.- 3. Magnetic neutron diffraction.- 4. Magnetic copper ordering.- 5. Magnetic rare-earth (R) ordering.- 6. Dipolar interactions and crystal-field effects.- 7. Discussion and conclusions.- Acknowledgements.- References.- Collective Magnetic Excitations of 4f Ions in R2-xCexCuO4 (R=Nd, Pr).- 1. Introduction.- 2. Theory of 4f magnetic excitations.- 3. Rare-earth magnetic properties in R2-xCexCuO4 (R=Nd,Pr).- 4. Dispersion of CEF excitations.- 5. Spin waves in Nd2-xCexCuO4.- 6. Conclusions.- Acknowledgements.- References.- The Crystal Field as a Local Probe in Rare-Earth Based Copper-Oxide Superconductors.- 1. Introduction.- 2. The crystal-field (CF) interaction.- 3. Examples.- 4. Doping effects.- 5. Linewidth of CF excitations.- 6. Conclusions.- Acknowledgements.- References.- Small-Angle Neutron Scattering Experiments on Vortices in Copper-Oxide Superconductors.- 1. History and introduction.- 2. The interaction between flux lines and neutrons.- 3. Experimental geometry for SANS.- 4. Flux lattice structure, orientation, pinning and melting.- 5. Experimental results on flux lattice structures in YBCO.- 6. Experimental results on flux lattice structures in BSCCO-2212.- 7. Flux lattice melting.- 8. Other information from diffraction.- 9. Neutron depolarisation.- 10. Comparison with other superconductors.- 11. Summary and outlook.- Acknowledgements.- References.