"The design of molecular nanoscale magnets is a hot topic research area due to their technological interest in high density data storage or quantum computing. In this field, lanthanide-containing systems are appealing due to the large magnetic moment and large anisotropy associated with most of the lanthanides, key factors determining the temperature below which single-molecule(SMMs) and single-chain magnets(SCMs) retain the magnetization due to its slow relaxation. Whereas 3d-based molecular nanomagnets have been largely studied and their relaxation mechanisms are well understood, little is known for their novel 4f-based counterparts. For this reason, the aim of this project is to fulfill this lack of knowledge in order to support a future rational design of 4f-based nanomagnets for technological applications. For that, several theoretical methods will be employed: Quantum Chemistry methods for computing the Stark sublevels of the lanthanide ions, theoretical models for describing the dynamics of the magnetization in 4f-based nanomagnets and statistical physic methods for modeling the behaviour of the 4f-based SCMs. Moreover, X-ray, spectroscopic and magnetic measurements will be needed in order to provide suitable experimental data for developing and testing the theoretical studies. Due to the profile of the project, LAMM laboratory, one of the world leader laboratories in molecular magnetism, is the ideal place for its accomplishment because the large experience in molecular synthesis, including lanthanide chemistry, and the expertise in combining theory and experiment in the study of molecular-based magnets, in particular in SMMs and SCMs. Finally, the realization of the project will complement the theoretical and experimental expertise of the applicant in order to develop an independent career in theoretical aspects of molecular magnetism and it will afford him to establish contacts with other European research groups for future collaborations."