Spin-orbit excitation energies, anisotropic exchange, and magnetic   phases of honeycomb RuCl3
  Using quantum chemistry calculations we shed fresh light on the electronic structure and magnetic properties of RuCl3, a proposed realization of the honeycomb Kitaev spin model. It is found that the nearest-neighbor Kitaev exchange K is weaker than in 5d5 Ir oxides but still larger than other effective spin couplings. The electronic-structure computations also indicate a ferromagnetic K in the halide, which is supported by a detailed analysis of the field-dependent magnetization. From exact-diagonalization calculations for extended Kitaev-Heisenberg Hamiltonians we additionally find that a transition from zigzag order to a spin-liquid ground state can be induced in RuCl3 with external magnetic field. 
Ravi Yadav, Nikolay A. Bogdanov, Vamshi M. Katukuri, Satoshi   Nishimoto, Jeroen van den Brink, Liviu Hozoi
cond-mat.str-el