One year ago the ESRF was in the midst of a long shutdown to carry out major construction work for Phase I of the Upgrade Programme. Although work continues, operation restarted back in May 2012 and many new experiments have been successfully performed since then. In the Electronic Structure and Magnetism Group, the first upgrade beamlines on BM23 and ID24 have gone into user operation enhancing our portfolio of beamlines. The upgrade continues for the group’s beamlines with the closure of the soft X-ray beamline ID08 in July 2013. It will be replaced by the new soft X-ray beamline being built on ID32. The construction has already started.

Amongst all this construction activity, the main business of producing scientific results has continued. The articles chosen for this year’s Highlights show the timely, topical and exciting work being done. They represent typical examples of the cutting-edge research being carried out and address a diverse range of important scientific questions. These range from heavy Fermions, topological insulators to dilute magnetic semiconductors, arsenic in soils and catalysts. A short introduction to the topics follows.

Studies of heavy Fermion materials have attracted interest for many decades. Below a characteristic temperature, the conduction electrons behave as if they have an effective mass several orders of magnitude larger than the free-electron mass (hence heavy). Typically compounds of Ce, U, Yb with localised f-electrons fall into this class of materials. Due to competing effects there are many possible ground states. Understanding the electronic properties of such materials is of basic interest and essential to explain their extraordinary properties, such as their low temperature resistivity. The highlight by Willers et al. shows how X-rays can help in understanding such properties, using the example of YbInNi4.

Topological insulators are fascinating materials in which the bulk of the material is insulating but the surface is metallic. Conducting surface states can arise due to special symmetry properties. For example, in the case of Bi2Se3, which is studied in the article by Honolka et al., spin-orbit coupling and time reversal lead to a surface conducting state in which the spin and the momentum of the electron are coupled. Two electrons moving in opposite directions will have reversed spins. This opens up interesting possibilities for spin electronic applications, as the topological surface state allows a spin current to move with little resistance.

Even before the discovery of topological insulators extensive efforts were employed to find suitable materials for spintronic applications. One area of investigation has been that of dilute magnetic semiconductors. The hope is that a material combining magnetic and semiconductor properties could be integrated in future semiconductor devices using the spin of the electron as an extra degree of freedom. However, it is often difficult to separate intrinsic properties from spurious sources of magnetism, e.g. magnetic impurities or clusters of magnetic atoms. X-ray studies using magnetic dichroism (XMCD) techniques allow both structural and magnetic properties to be measured. Importantly, X-ray dichroism studies are element specific giving vital additional information. A study of this type is described in the Highlight by Ney et al.

XMCD is also a highly sensitive method and this combined with its element specificity and access to high magnetic fields and low sample temperature allows for unique experiments. One such example is the study of Rh clusters by Narthem et al. where exchange enhanced Pauli paramagnetic properties are revealed.

Single walled carbon nanotubes, which are essentially like a graphene sheet folded into a cylinder, also have many novel properties. They are highly flexible and have a high tensile strength together with interesting electronic properties. There are many potential uses including nanotube transistors, solar cell applications, etc. By doping with halogens, the electronic properties can be modified, and that is the subject of the article by Chorro et al.

In a totally different vein, the article by Langner et al. addresses the environmental problem of arsenic contamination in the environment, where it is a threat to some of the world’s water resources. This is an important issue affecting millions of people in dozens of countries. To address this problem, an understanding of the biogeochemical cycle is needed and spectroscopic studies of soils can help in this respect, as is shown in the article.

The final two articles deal with chemical problems; one concerns the meso-sphere of complexes in solution and the other the study of catalytic materials under reaction conditions. Both combine results from several different techniques. The former combines neutron, X-ray results and Monte Carlo simulations; the latter X-ray diffraction, infrared and EXAFS results.

The meso-shell describes the solvation molecules, often water but not only, that surround a molecule in solution and influence its reactivity. Having a better understanding of this structure is important for synthesis and is addressed in the article by Bowron et al.

The Highlight by Kubacka et al. emphasises the importance of studying in situ and as close as possible to real catalytic systems using a multitechnique approach. The results are significant in the context of pollutant elimination in three-way conversion materials (TWC) used in car catalytic converters.

In order to continue to produce scientific results at the forefront of research, we need to further develop our capabilities. This is happening through Phase I of the Upgrade Programme and will hopefully continue in a Phase II, which is currently under discussion.

N.B. Brookes