Magnetic properties of Ag2VOP2O7:: An unexpected spin dimer system

Magnetic properties of the silver vanadium phosphate Ag2VOP2O7 are studied by means of magnetic susceptibility measurements and electronic structure calculations. In spite of the layered crystal structure suggesting one-dimensional or two-dimensional 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.