Using electronic structure changes to map the H-T phase diagram of α#prime#-NaV2O5

We report polarized optical reflectance studies of α#prime#-NaV2O5 as a function of temperature (4 - 45 K) and magnetic field (0 - 60 T). Rung directed electronic structure changes, as measured by near-infrared reflectance ratios ΔR(H)=R(H)/R(H=0 T), are especially sensitive to the phase boundaries. We employ these changes to map out an H-T phase diagram. Topological highlights include the observation of an additional phase boundary slightly below TSG, enhanced curvature of the 34 K phase boundary above 35 T, and, surprisingly, strong hysteresis effects of both transitions with applied field