Effects of intercluster coupling in high spin molecular magnets Original Research Article

We report evidences for long-range antiferromagnetic (AF) order in iron oxyhydroxides Fe19metheidi and (enH2)2Fe6 clusters that at low temperature behave like single molecule magnets with total spin S=33/2 and S=5, respectively. Anomalies are clearly observed at 1.19 K in the heat capacity and in the low-field magnetization of Fe19metheidi while for (enH2)2Fe6 a broad λ-peak is found at 0.99 K in the heat capacity. Since dipolar interactions are estimated to be ∼190 mK and ∼40 mK for Fe19metheidi and (enH2)2Fe6, respectively, the origin of the AF ordering is due to super-exchange in these cases.