Magnetic interactions and high-field properties of Ag₂VOP₂O₇: frustrated alternating chain close to the dimer limit

We report on high field magnetic properties of the silver vanadium phosphate Ag₂VOP₂O₇. This compound has a layered crystal structure, but the specific topology of the V-P-O framework gives rise to a one-dimensional spin system, a frustrated alternating chain. Low-field magnetization measurements and band structure calculations show that Ag₂VOP₂O₇ is close to the dimer limit with the largest nearest-neighbor interaction of about 30 K. High-field magnetization data reveal the critical fields µ₀H_c1 = 23 T (closing of the spin gap) and µ₀H_c2 = 30 T (saturation by full alignment of the magnetic moments). From H_c1 to H_c2 the magnetization increases sharply similar to the system of isolated dimers. Thus, the magnetic frustration in Ag₂VOP₂O₇ bears little influence on the high-field properties of this compound.