Abstracts 2005

Abstract of Publication No. 516

Journal Cover Picture, a516cover.jpg (61 kByte) Juan Modesto Clemente-Juan, Eugenio Coronado, Alejandro Gaita-Ariño, Carlos Giménez-Saiz, Hans-Ulrich Güdel, Andreas Sieber, Roland Bircher and Hannu Mutka
Magnetic Polyoxometalates: Anisotropic Exchange Interactions in the CoII3 Moiety of [(NaOH2)Co3(H2O)(P2W15O56)2]17-
Inorg. Chem. 44, 3389-3395 (2005)      Full Text (PDF)      DOI-Link      Journal Cover Picture     

Abstract: The magnetic exchange interactions in a CoII3 moiety encapsulated in Na17 [(NaOH2)Co3(H2O)(P2W15O56)2] (NaCo3) were studied by a combination of magnetic measurements (magnetic susceptibility and low-temperature magnetization), with a detailed Inelastic Neutron Scattering (INS) investigation. The novel structure of the salt was determined by X-ray crystallography. The ferromagnetic Co3O14 triangular cluster core consists of three octahedrally oxo-coordinated CoII ions sharing edges. According to the single-ion anisotropy and spin-orbit coupling usually assumed for octahedral CoII ions, the appropiate exchange Hamiltonian to describe the ground-state properties of the isosceles triangular Co3 spin cluster is anisotropic and is expressed as = - 2 a=x,y,zx,y,z (1a2a + 2a3a + 1a3a), where Ja are the components of the exchange interactions between the CoII ions. To reproduce the INS data, nonparallel anisotropic exchange tensors needed to be introduced, which were directly connected to the molecular symmetry of the complex. The following range of parameters (value ± 0.5 cm–1) was found to reproduce all experimental information while taking magnetostructural relations into account: = = 8.6 cm–1; = = 1.4 cm–1; = = 10.0 cm–1; = = 6.5 cm–1 and = 3.4 cm–1.

Cover Picture: The anisotropic exchange interactions in a ferromagnetic CoII3 moiety encapsulated in Na17[(NaOH2)Co3(H2O)(P2W15O56)2] were studied by a combination of magnetic measurements with a detailed Inelastic Neutron Scattering investigation. The cover shows the whole molecule and how the magnetic fragment interacts with a neutron beam, giving excitations in the low-energy magnetic levels.

Last modified: 13.12.11 by Gabriela Frei