Journal Covers

This schematic of x-ray scattering is from a spiral antiferromagnet with a spin structure that gives rise to domains with jamming behavior. Using resonant magnetic x-ray photon correlation spectroscopy, this research shows that the domains of a spiral antiferromagnet enter a jammed state at the onset of long-range order. Researchers found that slow thermal fluctuations of the domain walls exhibit a compressed exponential relaxation with an exponent of 1.5 found in a wide variety of solid-like jammed systems and can be qualitatively explained in terms of stress release in a stressed network. As the temperature decreases, the energy barrier for fluctuations becomes large enough to arrest further domain wall fluctuations, and the domains freeze into a spatial configuration within 10 K of the Néel temperature. The relaxation times can be fitted with the Vogel-Fulcher law as observed in polymers, glasses, and colloids, thereby indicating that the dynamics of domain walls in an ordered antiferromagnet exhibit some of the universal features associated with jamming behavior. Read more »

Spin-coating is extensively used in the lab-based manufacturing of organic solar cells, including most of the record-setting cells. Aram Amassian and co-workers report in this study the first direct observation of photoactive layer formation as it occurs during spin-coating. The study provides new insight into mechanisms and kinetics of bulk heterojunction formation, which may be crucial for successful transfer to printing processes and scaling up production. Read more »

Gathering information on the evolution of small cracks in ceramic matrix composites used in hostile environments such as in gas turbines and hypersonic flights has been a challenge. It is now shown that sequences of microcrack damage in ceramic composites under load at temperatures up to 1,750 °C can be fully resolved with the use of in situ synchrotron x-ray computed microtomography. Read more »