Magnetic Properties of Coupled Lanthanide-Radical Species

Abstract

Systems containing rare-earth ions interacting with paramagnetic centers different from the lanthanide themselves are not common. Beyond garnets, orthochromites, and orthoferrites, only recently reports of exchanging trimers constituted by Cu₂ -Gd units were published^1,2,3. In these compounds a weak ferromagnetic interaction whithin the Cu-Gd pairs was observed while an antiferromagnetic one was reported for the Cu-Cu pair. The nature of the observed exchange interactions is not fully understood especially for the spin coupling involving f and d electrons. As lanthanides can play an important role in detremining the properties of new magnetic materials, it is in our opinion a relevant task to attempt a detailed study of the interactions through f orbitals. An useful tool for this work could be to use stable organic radicals as paramagnetic ligands toward rare-earth ions. As, for instance, in stable nitroxide radicals the unpaired electron is largely delocalized on the oxygen atoms which is the donor one, in case of magnetic interaction, this should be a direct one, giving first hand informations on the bonding situation and the coupling pathway.