Intracluster interactions in “butterfly” {Fe3LnO2} molecules

The magnetization contributions of the Fe3 and Ln subcluster in the “butterfly” molecule [Fe3Ln(μ3-O)2(CCl3COO)8(H2O)(THF)3], in brief {Fe3LnO2}, with Ln=Lu, Gd, Tb, Dy and Ho, have been determined by a combination of vibrating sample magnetometry and x-ray circular magnetic dichroism at low temperature and magnetic field up to 14 T. These contributions have been explained in terms of an effective spin model where the Fe3 is described by a SFe3=5/2SFe3=5/2 spin, Gd by an isotropic J=7/2, Dy by a Kramers doublet, and non-Kramers ions Tb and Ho by a ligand field split doublet. The intracluster interactions JFeLn have been found to amount to a few K.