Low-temperature spin diffusion in a highly ideal S=1/2 Heisenberg antiferromagnetic chain studied by muon spin relaxation

The organic radical-ion salt DEOCC-TCNQF4 contains linear chains of stacked molecules with significant Heisenberg antiferromagnet interactions along the chain and extremely weak interactions between the chains. Zero-field muSR has confirmed the absence of long-range magnetic order down to 20 mK and field-dependent muSR is found to be consistent with diffusive motion of the spin excitations. The anisotropic spin dynamics and the upper boundary for magnetic ordering temperature both indicate interchain magnetic coupling /J'/<7 mK. As the intrachain coupling J is 110 K, /J'/J/ is significantly less than 10(-4). This system therefore provides one of the most ideal examples of the one-dimensional S=1/2 Heisenberg antiferromagnet yet discovered.     

Characterization of corrugated feed horns at 216 and 300 GHz

We present measurements of the near-field beam profiles of two corrugated feed horns with center frequencies of 216 and 300 GHz. Both co-polar and cross-polar components of the electric field have been probed across the operation band of the horns. A full-wave numerical near-field transformation, based on a vector Kirchhoff integral, is implemented to transform the measured field to the horn aperture for a comparison with the ideal aperture field. From the overlap integral of the transformed and the ideal field, we conclude that the field radiated by these horns is the HE₁₁ mode, to a purity of better than 99%.     

WASAN: The development of a facilitated methodology for structuring a waste minimisation problem

This paper contributes a new methodology called Waste And Source-matter ANalyses (WASAN) which supports a group in building agreeable actions for safely minimising avoidable waste. WASAN integrates influences from the Operational Research (OR) methodologies/philosophies of Problem Structuring Methods, Systems Thinking, simulation modelling and sensitivity analysis as well as industry approaches of Waste Management Hierarchy, Hazard Operability (HAZOP) Studies and As Low As Reasonably Practicable (ALARP). The paper shows how these influences are compiled into facilitative structures that support managers in developing recommendations on how to reduce avoidable waste production. WASAN is being designed as Health and Safety Executive Guidance on what constitutes good decision making practice for the companies that manage nuclear sites. In this paper we report and reflect on its use in two soft OR/problem structuring workshops conducted on radioactive waste in the nuclear industry.     

Organic Magnetic Materials Studied by Positive Muons

Positive muons can be implanted into organic and molecular magnets in order to study their internal magnetic field distribution and any associated dynamics. The muon behaves essentially as a microscopic magnetometer, sensitive to local magnetic order and magnetic fluctuations. We describe some recent experiments using this technique which were performed on a variety of organic systems, including nitronyl nitroxide magnets and materials with spin-Peierls ground states, MEM(TCNQ)₂ and DEM(TCNQ)₂, and demonstrate how the technique can give information concerning their ground states.