| High magnetic fields induce unusual phenomena in low-dimensional and/or frustrated spin systems. Magnetic excitations in such systems can be treated as bosons. At low temperatures, these bosons either undergo Bose-Einstein condensation or form Mott insulating phases giving rise to field-induced long-range ordering and plateaus in the magnetization curves, respectively. The combination of the two phenomena should result in a supersolid state that, however, has never been observed experimentally. The study and interpretation of the high-field properties of different model compounds remains a challenging problem in the field. In this contribution, we present high-field properties of Ag2VOP2O7, a spin-1/2 frustrated alternating chain compound. Theoretical results for the model suggest the possibility of the magnetization plateau at half saturation. However, the experimental magnetization curve of Ag2VOP2O7 does not show any plateau-like features and reveals the high-field behavior typical for a system of weakly coupled dimers. At low fields, the magnetization is close to zero due to the spin gap. The gap is closed at μOHc1 ≅ 23 T, and above Hc1 the magnetization increases in a linear fashion until the saturation is reached at μ0Hc2 ≅ 30 T. The Hc1 and Hc2 values are in perfect agreement with the set of the exchange coupling constants, as derived from low-field magnetization data and band structure calculations: J1 ≅ 35 K, J'1 ≅ K (nearest-neighbor interactions) and J2 ≅ 5 K (next= -nearest-neighbor interaction). Thus, Ag2VOP2O7 is close to the dimer limit of the frustrated alternating chain, and magnetic frustration bears little influence on the high-field properties of this compound. |
|