Magnetic chains of Fe clusters in the {FeYO} butterfly molecular compound.

The "butterfly" molecule [Fe3Y(μ3-O)2(CCl3COO)8(H2O)(THF)3] (in brief {Fe3YO2}) includes three Fe3+ ions which build a robust Fe3 cluster with a strong intracluster antiferromagnetic exchange and a total spin S = 5/2. It represents the starting magnetic system to study further interactions with magnetic rare earths when Y is replaced with lanthanides. We present heat capacity and equilibrium susceptibility measurements below 2 K, which show that each cluster has a sizeable magnetic anisotropy pointing to the existence of intercluster interactions.