Fe-57-NMR determination of the local magnetic structure of the molecular nanomagnet Fe8

Fe-57 nuclear magnetic resonance (NMR) measurements have been carried out in Fe-57-enriched Fe8 clusters to investigate microscopically the magnetic internal spin structure of the cluster in its high-spin S=10 ground state. In zero field, eight different NMR lines are observed at 1.5 K in the frequency range 63-73 MHz, indicating a total lack of symmetry in the Fe8 cluster. From the external magnetic field dependence of the Fe-57 NMR spectrum, applied both parallel and perpendicular to the easy axis, the ferrimagnetic spin configuration is confirmed and its rigid rotation, when the external magnetic field is applied perpendicular to the easy axis, is evidenced.