Hyperfine coupling and slow magnetic relaxation in isotopically enriched DyIII mononuclear single-molecule magnets

Abstract

The four main stable isotopes of the [ADy(tta)3(L)]·C6H14 (ADy with A = 161-164) Single-Molecule Magnet (SMM) (tta- = 2-thenoyltrifluoroacetylacetonate and L = 2-{[2-methylpyridiyl]-4,5-[4,5-bis(propylthio)-tetrathiafulvalenyl]-1H-benzimidazol-2-yl}pyridine) have been magnetically investigated and structurally characterized by single crystal X-ray diffraction. The two nuclear spin-free 162/164Dy behave the same from a dynamic magnetic point of view and with slower magnetic relaxation than the two pure magnetically active isotopically substituted 161/163Dy. In addition, this paper demonstrates that 161Dy and 163Dy relax differently even if they both carry I = 5/2 nuclear spin. After the release of the dipolar interactions through magnetic dilution, ([161Dy0.05Y0.95(tta)3(L)]·C6H14) (161Dy@Y) relaxes four times slower than 163Dy@Y due to different hyperfine coupling constants.