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