Low-temperature magnetic interactions in the “butterfly”-type {Fe3GdO2} compound: The persistence of magnetic chains

Heat capacity measurements on the Ln = Gd case of the butterfly molecule series [Fe3Ln(μ3–O)2 (CCl3COO)8(H2O)(THF)3], in brief {Fe3LnO2}, are presented. In the previously studied {Fe3YO2} butterfly, where the magnetic properties stem only from the Fe3+ ions, magnetic chains of spin-5/2 Fe3Y clusters had been identified and described. The substitution of the nonmagnetic Y3+ ion by the magnetic Gd3+ adds magnetic interactions to the clusters, but not magnetic anisotropy. The heat capacity measurement shows an excess over the contribution of the antiferromagnetically coupled Fe3Gd magnetic clusters at very low temperature, which can be described as magnetic spin-1 chains using a Blume–Capel model. The intercluster interaction constant J ch = − 55 ( 5 ) mK is very similar to that of {Fe3YO2}, which shows that the interaction is mainly controlled by the magnitude of the cluster’s magnetic moment.