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The Magnetic Behaviour of [N n Bu 4 ] 4 [Ni 16 Pd 16 (CO) 40 ]: An Even‐Electron Homoleptic Carbonyl–Metal Cluster Anion Displaying a J =2 Ground State
Author(s) -
Riccò Mauro,
Shiroka Toni,
Carretta Stefano,
Bolzoni Fulvio,
Femoni Cristina,
Iapalucci M. Carmela,
Longoni Giuliano
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400874
Subject(s) - condensed matter physics , muon spin spectroscopy , magnetization , magnetometer , paramagnetism , magnetic moment , chemistry , magnetism , magnetic susceptibility , physics , magnetic field , superconductivity , quantum mechanics
The magnetic behaviour of the even‐electron [Ni 16 Pd 16 (CO) 40 ] 4− cluster, in its [N n Bu 4 ] + salt, has been investigated by magnetometry and muon spin rotation/relaxation (μSR) spectroscopy. The susceptibility measurements show an exceptionally high magnetic moment corresponding to a total spin value J =2. This suggests a Hund filling of a quadruplet ground state, quite unique in carbonyl–metal clusters. SQUID magnetometry shows a departure from the Curie–Weiss law, for T >150 K, and strong deviation from a Brillouin behaviour of the magnetisation curves. μSR spectroscopy in zero applied field shows a temperature independent decay of the muon spin polarisation, similar to that of a purely paramagnetic system. The observed muon spin repolarisation in a moderate external longitudinal field, however, invalidates this simple picture and suggests the presence of a local anisotropy field acting on the cluster's magnetic moment. A consistent interpretation of magnetometry and μSR results implies the occurrence of an additional interaction of the cluster spin with an effective crystalline field. The inclusion of this interaction in a model Hamiltonian allows us to successfully reproduce both the susceptibility and magnetisation data.