On the importance of ferromagnetic exchange between transition metals in field-free SMMs: examples of ring-shaped hetero-trimetallic [(LnNi2){W(CN)8}]2 compounds

Rare cases of genuine (i.e. field-free) SMM have been found for mixed 3d-4f-5d ring-shaped compounds with Tb(III) (U-eff/k(B) = 23.0 K) or Dy(III) (U-eff/k(B) = 26.4 K). The ferromagnetic interactions between the transition metals are shown to play an essential role in this feature.