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, ([¹⁶¹Dy_0.05Y_0.95(tta)₃(L)]·C₆H₁₄) (¹⁶¹Dy@Y) relaxes four times slower than ¹⁶³Dy@Y due to different hyperfine coupling constants.