Magnetic Field Induced Transitions from Spin Glass to Liquid to Long Range Order in a 3D Geometrically Frustrated Magnet

Gadolinium gallium garnet, ${\mathrm{Gd}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$, has an extraordinary low temperature phase diagram including a spin glass phase near $H=0\mathrm{}\mathrm{T}$, an antiferromagnetic (AFM) phase for $0.7\le H\le 1.4\mathrm{T}$, and, at intermediate fields, an apparent spin-liquid state without long range order. We have characterized the intermediate field (IF) state through heat capacity, thermal conductivity, and magnetocaloric measurements. Our results indicate that the IF phase is distinct from the spin glass, and that the phase boundary between the AFM and IF phases has a distinct minimum at $T\sim 0.18\mathrm{K}$, in analogy to the minimum in the melting curve of ${}^4\mathrm{He}$.