Coexistence of spin liquid state and magnetic correlations in 3d-5d based triangular-lattice antiferromagnet Sr 3 CuIr 2 O 9

Here, we report detailed lattice structure, magnetization (dc and ac) and specific heat measurements on a 3 d -5 d based new triple-perovskite material Sr 3 CuIr 2 O 9 . The Sr/Cu forms a layered structure of triangular-lattice while the Ir forms Ir 2 O 9 dimers which lie in chain as well as simultaneously makes layered triangular-lattice with neighboring atoms. Due to random site-sharing with Sr 2+ , the Cu 2+ (3 d 9 , spin-1/2) forms a diluted magnetic lattice, thus giving a disordered in-plane exchange interaction. Opposed to conventional J e f f model, the Ir 5+ (5 d 4 , J e f f = 0) is believed to be magnetic here which participates both in-chain and in-plane magnetic interactions. This complex lattice structure driven competing exchange interaction leads the ground state to a gapless quantum-spin-liquid state which coexists with (weak) ferromagnetic spin correlations. While underling the importance of spin state (spin-1/2), we believe that the combined effect of lattice structure, geometric frustration, spin–orbit coupling and spin state has given rise this interesting ground state in this material.