What neutrons do tell us about the nature of (spin)glasses?

Complete text of publication follows. The crucial role of neutron scattering experiments in the study of glassy phenomena is due to the capability of exploring microscopic dynamics directly in space and time. To do this in practice is much more difficult in disordered or amorphous systems though, since we cannot take advantage of the very handy consequences of translational symmetry. Nevertheless, the importance of the interplay between different length scales is being more and more recognized as a key feature of the understanding of disordered and complex matter. A common feature of all glassy systems is the decisive role of dynamics in determining the evolution of macroscopic properties, while the short and eventually partial long range order shows little difference between the different phases. Recent results on Cu-Mn spin glass dramatically illustrate this point, and provide unambiguous evidence against recent suggestions that behavior in Cu-Mn is driven by spin density waves. Recent findings in Au-Fe provide the first circumstantial evidence for the theoretically predicted extremely long correlation lengths at the spin glass transition. A new computer aided experimental strategy has been developed in order to control multiple scattering noise. It opened up the way to investigate dynamics in glasses and liquids on extended length scales, where only spin correlations could be studied by now. The first results reveal that, similarly to spin glasses, extra relaxation channels are of great importance. (author)