Structural and magnetic dimers in the spin-gapped systemCuTe2O5

We investigated the magnetic properties of the system CuTe2O5 by\nsusceptibility and electron spin resonance measurements. The anisotropy of the\neffective g-factors and the ESR linewidth indicates that the anticipated\nstructural dimer does not correspond to the singlet-forming magnetic dimer.\nMoreover, the spin susceptibility of CuTe2O5 can only be described by taking\ninto account interdimer interactions of the same order of magnitude than the\nintradimer coupling. Analyzing the exchange couplings in the system we identify\nthe strongest magnetic coupling between two Cu ions to be mediated by\nsuper-super exchange interaction via a bridging Te ligand, while the\nsuperexchange coupling between the Cu ions of the structural dimer only results\nin the second strongest coupling.\n