Synthesis, disorder and Ising anisotropy in a new spin liquid candidate PrMgAl_11O_19

Here we report the successful synthesis of large single crystals of triangular frustrated PrMgAl_11O_19 using the optical floating zone technique. Single crystal X-ray diffraction measurements unveiled the presence of quenched disorder within the mirror plane, specifically ∼7% of Pr ions deviating from the ideal 2d site towards the 6h site. Magnetic susceptibility measurements revealed an Ising anisotropy with the c-axis being the easy axis. Despite a large spin-spin interaction that develops below ∼10 K and considerable site disorder, the spins do not order or freeze down to at least 50 mK. The availability of large single crystals offers a distinct opportunity to investigate the exotic magnetic state on a triangular lattice with an easy axis out of the plane.