Magnetism and magnetic anisotropy of spin clusters

This thesis is organized as follows: Chapter 2 is dedicated to a brief survey of the main features of HF-EPR, while in Chapter 3 calculation models of spin hamiltonian mainly based on ligand field theories will be covered. Particular attention will be paid to the Angular Overlap Model, which we have employed with some success in the rationalization of anisotropic properties of both isolated transition metal ions and of spin clusters. In Chapter 4 the results of a thorough multitechnique approach to characterize anisotropic properties and spin dynamics of description of the properties a new SMM of apparent structural simplicity will be presented. Finally the metal-radical approach is faced in Chapter 5 and 6 by magnetically characterizing several systems containing semiquinones radical ligands. In the former chapter the use of polyradical ligands as suitable building blocks to create new extended lattices is investigated whereas in the latter the structural and magnetic properties of a simple series of rare-earths containing complexes will be investigated with the aim of obtaining some useful hints for the rationalization of the magnetic coupling in these systems.