Synthesis of the Elusive = / Star Structure: A Possible Quantum Spin Liquid Candidate.

Materials with two-dimensional, geometrically frustrated, spin-/ lattices provide a fertile playground for the study of intriguing magnetic phenomena such as quantum spin liquid (QSL) behavior, but their preparation has been a challenge. In particular, the long-sought, exotic spin-/ star structure has not been experimentally realized to date. Here we report the synthesis of [(CH)(NH)][Cu(μ-OH)(μ-SO)(μ-SO)]·0.24HO with an = / star lattice. On the basis of the magnetic susceptibility and heat capacity measurements, the layered Cu-based compound exhibits antiferromagnetic interactions but no magnetic ordering or spin freezing down to 2 K. The spin-frustrated material appears to be a promising QSL candidate.