Abstract
We present inelastic neutron-scattering data on the quantum paramagnet AgVOAsO4 that establish this system as a S=1/2 alternating spin chain compound and provide a direct measurement of the spin gap Δ=1.2meV. We also present experimental evidence for two different types of field-induced magnetic order between μ0Hc1=8.4T and μ0Hc2=48.9T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H−T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 and 5.3 K, respectively. This complex phase diagram is not expected for a single-→Q BEC system and therefore establishes AgVOAsO4 as a promising multi-→Q BEC candidate capable of hosting exotic vortex phases.
