MAGNETIC EXCITATIONS IN POLYOXOMETALATE TETRAMERIC CLUSTERS

The metal-oxide clusters with formula [M-4(D2O)(2)(PW9O34)(2)](10-) wh ich contain a tetrameric magnetic cluster M4O16 provide an ideal serie s for the study of magnetic exchange interactions in polymetallic mole cular clusters. To get a more direct information on the splitting of t he spin states caused by the exchange interactions we have performed i nelastic neutron scattering measurements on the Co, Mn and Ni clusters . Magnetic excitations have been observed in the range 0.5-6 meV. A te ntative interpretation of these data from a Heisenberg exchange Hamilt onian and a single ion zero-field splitting is presented for Ni cluste r.