Structural magnetic glassiness in the spin ice Dy2 Ti2 O7

The origin and nature of glassy dynamics presents one of the central enigmas of condensed-matter physics across a broad range of systems ranging from window glass to spin glasses. The spin-ice compound Dy2Ti2O7, which is perhaps best known as hosting a three-dimensional Coulomb spin liquid with magnetically charged monopole excitations, also falls out of equilibrium at low temperature. How and why it does so remains an open question. Based on an analysis of low-temperature diffuse neutron-scattering experiments employing different cooling protocols alongside recent magnetic noise studies, combined with extensive numerical modeling, we argue that upon cooling, the spins freeze into what may be termed a "structural magnetic glass,"without an a priori need for chemical or structural disorder. Specifically, our model indicates the presence of frustration on two levels, first producing a near-degenerate constrained manifold inside which phase ordering kinetics is in turn frustrated. A remarkable feature is that monopoles act as sole annealers of the spin network and their pathways and history encode the development of glass dynamics, allowing the glass formation to be visualized. Our results suggest that spin ice Dy2Ti2O7 provides one prototype of magnetic glass formation specifically and a setting for the study of kinetically constrained systems more generally

Improving leadership in higher education institutions : a distributed perspective

This paper reports on a qualitative study exploring how distributed patterns of leadership manifest themselves in project teams within a Higher Education institution. The emphasis is on both the &lsquo;what&rsquo; and the &lsquo;how&rsquo; of distributed leadership, thus providing an account of the nature of distributed leadership in higher education and the factors which were found to enhance and inhibit its occurrence and effectiveness. The findings are presented in a model of distributed leadership which seeks to provide an integrative account and a framework for further study. The conclusions focus on both the theoretical implications for the study of distributed leadership and the practical implications for HE institutions wishing to promote effective leadership.<br /