Excitation of local magnetic moments by tunnelling electrons

The advent of milli-kelvin scanning tunneling microscopes (STM) with inbuilt magnetic fields has opened access to the study of magnetic phenomena with atomic resolution at surfaces. In the case of single atoms adsorbed on a surface, the existence of different magnetic energy levels localized on the adsorbate is due to the breaking of the rotational invariance of the adsorbate spin by the interaction with its environment, leading to energy terms in the meV range. These structures were revealed by STM experiments in IBM Almaden in the early 2000's for atomic adsorbates on CuN surfaces. The experiments consisted in the study of the changes in conductance caused by inelastic tunnelling of electrons (IETS, Inelastic Electron Tunnelling Spectroscopy). Manganese and Iron adatoms were shown to have different magnetic anisotropies induced by the substrate. More experiments by other groups followed up, showing that magnetic excitations could be detected in a variety of systems: e.g. complex organic molecules showed that their magnetic anistropy was dependent on the molecular environment, piles of magnetic molecules showed that they interact via intermolecular exchange interaction, spin waves were excited on ferromagnetic surfaces and in Mn chains, and magnetic impurities have been analyzed on semiconductors. These experiments brought up some intriguing questions: the efficiency of magnetic excitations was very high, the excitations could or could not involve spin flip of the exciting electron and singular-like behavior was sometimes found at the excitation thresholds. These facts called for extended theoretical analysis; perturbation theories, sudden-approximation approaches and a strong coupling scheme successfully explained most of the magnetic inelastic processes. In addition, many-body approaches were also used to decipher the interplay between inelasComment: Review article to appear in Progress of Surface Scienc

Reinterpreting the Elephant: Reclaiming Craft in the City

Reinterpreting the Elephant is about the reinterpretation of abandoned industrial buildings in the city of Liège. Through proposing a craft school in Bressoux, a neighbourhood of Liège, the project tries to reclaim craft in the city and give the city a new chance. By reusing an existing abandoned industrial building and reinterpreting the features of these 'elephants' the new building is shaped.Architecture, Urbanism and Building Sciences | Architectural Engineerin

Stacking Stories to Upgrade the City: The Role of High-rise Buildings in Rotterdam

With the exponential growth of high-rise buildings in Rotterdam over the past decades the city is now the 10th highest city in Europe. The role that high-rise plays in the city of Rotterdam has been developing throughout the years and started becoming more important. Through literature and municipal archival research, the significance of high-rise buildings and their role have been explored through three different aspects: cultural physical and economical. High-rise buildings emerged from the culture of congestion but were merely used as a tool for the densification of the city after World War II. While the early urban planning did not address high-rise buildings it laid down the urban foundation for the designated high-rise zones in the city. With the exponential growth the municipality set up policies for high-rise buildings to keep the built environment in check. Because of the lack of historic city value of Rotterdam, the high-rise buildings and structures form the iconic image of the city. While high-rise buildings fulfil their role of accommodating people it also functions as a tool for city branding to not only promote the city but also revitalize the built environment However, high-rise buildings can also have a negative impact on the social wellbeing of its users. Both anonymity and the lack of connection with the public realm high-rise buildings can bring more harm than good to its users. Although the municipality is already addressing this problem in their most recent high-rise policy and urban planning it appears from this research that it is important to explore how high-rise buildings can sustain communities and the future generations.AR2A011Architecture, Urbanism and Building Science