1. Molecular Electronics and Photonics, INPAC, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium, University Hasselt and Transnational University Limburg, BIOMED, Agoralaan Building C, B-3590 Diepenbeek, Belgium, and Nanoscale Superconductivity and Magnetism & Pulsed Fields Group, INPAC, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium