Single Molecule Magnetism with Strong Magnetic Anisotropy and Enhanced Dy???Dy Coupling in Three Isomers of Dy-Oxide Clusterfullerene Dy₂O@C₈₂.

ABSTRACT: A new class of single-molecule magnets (SMMs) based on Dy-oxide clusterfullerenes is synthesized. Three isomers of Dy₂O@C₈₂ with C _s(6), C _3v(8), and C _2v(9) cage symmetries are characterized by single-crystal X-ray diffraction, which shows that the endohedral Dy-(µ₂-O)-Dy cluster has bent shape with very short Dy-O bonds. Dy₂O@C₈₂ isomers show SMM behavior with broad magnetic hysteresis, but the temperature and magnetization relaxation depend strongly on the fullerene cage. The short Dy-O distances and the large negative charge of the oxide ion in Dy₂O@C₈₂ result in the very strong magnetic anisotropy of Dy ions. Their magnetic moments are aligned along the Dy-O bonds and are antiferromagnetically (AFM) coupled. At low temperatures, relaxation of magnetization in Dy₂O@C₈₂ proceeds via the ferromagnetically (FM)-coupled excited state, giving Arrhenius behavior with the effective barriers equal to the AFM-FM energy difference. The AFM-FM energy differences of 5.4-12.9 cm^-1 in Dy₂O@C₈₂ are considerably larger than in SMMs with {Dy₂O₂} bridges, and the Dy???Dy exchange coupling in Dy₂O@C₈₂ is the strongest among all dinuclear Dy SMMs with diamagnetic bridges. Dy-oxide clusterfullerenes provide a playground for the further tuning of molecular magnetism via variation of the size and shape of the fullerene cage.

SUBMITTER: Yang W 

PROVIDER: S-EPMC6794633 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature