Abstracts 2002

Abstract of Publication No. 441

Juan M. Clemente-Juan, Eugenio Coronado, Alejandro Gaita-Ariño, Carlos Giménez-Saiz, Grégory Chaboussant, Hans-Ulrich Güdel, Ramón Burriel and Hannu Mutka
Magnetism in Polyoxometalates: Anisotropic Exchange Interactions in the CoII3 Moiety of [Co3W(D2O)2(ZnW9O34)2]12- - A Magnetic and Inelastic Neutron Scattering Study
Chem. Eur. J. 8, 5701-5708 (2002)      Full Text (PDF)      DOI-Link     

Abstract: The ground-state properties of a CoII3 moiety encapsulated in a polyoxometalate anion were investigated by combining measurements of specific heat, magnetic susceptibility, and low-temperature magnetization with a detailed inelastic neutron scattering (INS) study on a fully deuterated polycrystalline sample of Na12[Co3W(D2O)2(ZnW9O34)2]·40 D2O (Co3). The ferromagnetic Co3O14 cluster core consists of three octahedrally oxo-coordinated CoII ions. According to the single-ion anisotropy and spin-orbit coupling of the octahedral CoII ions, the appropriate exchange Hamiltonian to describe the ground-state properties of the Co3 spin cluster is anisotropic and is expressed as H = -2 Sa=x,y,z (Ja121a2a + Ja232a3a), where Ja are the components of the exchange interactions between the CoII ions. To reproduce the INS data, different orientations of the two anisotropic J tensors must be considered, and the following conditions had to be introduced: Jx12=Jy23, Jy12=Jx23, Jz12=Jz23. This result was correlated with the molecular symmetry of the complex. The following set of parameters was obtained: Jx12=Jy23=1.37, Jy12=Jx23=0.218, and Jz12=Jz23=1.24 meV. This set also reproduces in a satisfactory manner the specific heat, susceptibility, and magnetization properties of Co3.

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