  Magnetic properties of the silver vanadium phosphate Ag(2)VOP(2)O(7) are
studied by means of magnetic susceptibility measurements and electronic
structure calculations. In spite of the layered crystal structure suggesting 1D
or 2D magnetic behavior, this compound can be understood as a spin dimer
system. The fit of the magnetic susceptibility indicates an intradimer
interaction of about 30 K in perfect agreement with the computational results.
Our study emphasizes the possible pitfalls in interpreting experimental data on
structural basis only and points out the importance of microscopic models for
the understanding of the magnetic properties of vanadium phosphates.
