Opportunities for New Physics in Molecular Magnetism

Abstract

The title of this discussion report is rather challenging and broad. It covers both theoretical and experimental aspects of molecule-based materials from the physical view point. As is well known, the discovery of the Curie law dates to the end of the last century, and magnetism has been receiving continuous interest over 100 years, both on the theoretical and experimental grounds. However, it is only in the past decade that molecule-based magnetism became a challenging part of magnetism. In fact, several interesting breakthroughs have now been made the most relevant of which can be considered the discovery of the molecule-based ferromagnets and ferrimagnets, and pure organic ferromagnets, which are reviewed in other chapters of this book. The main interest for these new materials arises from the fact that the interacting spins are in molecular orbitals (MO) with large or dominant role of s and p orbitals rather than d- and f electron bands in ordinary magnets. Therefore both organic and inorganic molecule-based magnetic systems should be commonly understood by using the MO concepts from the outset. This has lead to the adjustment of many concepts and rules originally elaborated for inorganic materials. It can be a matter of personal taste to decide whether these new concepts provided qualitative differences with the previous models, but, in our opinion, there is no doubt that many new objets have appeared in magnetism, both on the experimental and on the theoretical side, providing now a new field which requires, original approaches. In this report we will try to provide a unitary frame for possible developments of the field, also taking into account the main themes of interest of solid state physics at the moment.