MAGNETIC EXCITATIONS IN AN EXCHANGE-COUPLED TETRAMER CLUSTER OF COBALT(II) - A STUDY BY INELASTIC NEUTRON-SCATTERING

The polyoxometalate K10[Co4(H2O)2(PW9O34)2].20H2O contains a ferromagnetically exchange-coupled tetramer of Co(II) encapsulated in between two diamagnetic molecules (PW9O34)-9. At 2.5 K several inelastic peaks are observed in the energy range 1.5 7 meV, which are assigned to magnetic excitations in the cluster. A tentative interpretation of these data from an anisotropic exchange model yields a cobalt-cobalt interaction of 3 meV (24 cm-1) and an amount of anisotropy J(xy)/J(Z) congruent-to 0.6. These values are consistent with the magnetic susceptibility measurements.