Frustrated Ising chains on the triangular lattice in Sr$_3$NiIrO$_6$
  Inelastic neutron scattering study on the spin-chain compound Sr$_3$NiIrO$_6$ reveals gapped quasi-1D magnetic excitations. The observed one-magnon band between 29.5 and 39 meV consists of magnon modes of the Ni$^{2+}$ ions. The fitting of the spin wave spectrum reveals strongly coupled Ising-like chains along the $c$-axis that are weakly coupled into a frustrated triangular lattice in the $ab$-plane. The magnetic excitations survive up to 200 K well above the magnetic ordering temperature of $T_N \sim 75$ K, also indicating a quasi-1D nature of the magnetic interactions in Sr$_3$NiIrO$_6$. Our microscopic model is in good agreement with ab initio electronic structure calculations and explains the giant spin flip field observed in bulk magnetization measurements. 
S. Toth, W. Wu, D. T. Adroja, S. Rayaprol, E. V. Sampathkumaran
cond-mat.str-el