Magnetic Properties of Endohedral Metallofullerenes: Single-Molecular Magnetism and Anisotropy

Endohedral metallofullerenes (EMFs) encapsulating lanthanide ions (Ln) are of particular interest because of the specific magnetic properties resulting from the combination of the partially filled 4f shell of metal ions, their exchange interactions in endohedral clusters, and shielding role of the carbon cage, which protects endohedral spin states from the outer environment. Inhomogeneous environment of Ln ions inside clusterfullerenes induces magnetic anisotropy and results in a number of magnetic phenomena. In particular, Dy-based nitride clusterfullerenes are the first EMFs to exhibit single molecular magnet (SMM) behaviour.¹ Furthermore, completely different SMM behaviour of DySc₂N@C₈₀, Dy₂ScN@C₈₀, and Dy₃N@C₈₀ molecules shows that exchange interactions between Ln ions in EMFs has strong influence on the magnetic properties.² Results of the SQUID and XMCD studies of different EMFs at low temperatures will be discussed in this contribution. Whereas SQUID and XMCD are of particular use for the study of the low-temperature effects, magnetic properties of EMFs at room-temperature are conveniently addressed by paramagnetic NMR spectroscopy,³ since paramagnetic chemical shift is proportional to the anisotropy of magnetic susceptibility. New results on the NMR studies for a series of LnSc₂N@C₈₀molecules will be reported.

1. R. Westerström, J. Dreiser, C. Piamonteze, M. Muntwiler, S. Weyeneth, H. Brune, S. Rusponi, F. Nolting, A. Popov, S. Yang, L. Dunsch and T. Greber, J. Am. Chem. Soc., 2012, 134, 9840-9843.

2. R. Westerström, J. Dreiser, C. Piamonteze, M. Muntwiler, S. Weyeneth, K. Krämer, S.-X. Liu, S. Decurtins, A. Popov, S. Yang, L. Dunsch and T. Greber, arXiv:cond-mat/0604365v1, 2013, 1310.5040.

3. Y. Zhang, A. A. Popov, S. Schiemenz and L. Dunsch, Chem.-Eur. J., 2012, 18, 9691-9698.