Magnetic frustration in iridium spinel compound CuIr$_2$S$_4$
  We demonstrate via a muon spin rotation experiment that the electronic ground state of the iridium spinel compound, CuIr$_2$S$_4$, is not the presumed spin-singlet state but a novel paramagnetic state, showing a quasistatic spin glass-like magnetism below ~100 K. Considering the earlier indication that IrS$_6$ octahedra exhibit dimerization associated with the metal-to-insulator transition below 230 K, the present result suggests that a strong spin-orbit interaction may be playing an important role in determining the ground state that accompanies magnetic frustration. 
K. M. Kojima, 2 R. Kadono, M. Miyazaki, M. Hiraishi, I. Yamauchi, A.   Koda, Y. Tsuchiya, H. S. Suzuki, and H. Kitazawa
cond-mat.str-el