Abstract:

Cobaltates with j_eff = 1/2 ions recently drew attention as a platform for the celebrated Kitaev honeycomb model. Using a combination of neutron scattering and ab initio methods we extract magnetic couplings of Co²⁺ ions in recently synthesized SrCoGe₂O₆, a member of pyroxene family. We argue that staggered chains of edge-sharing octahedra surrounding magnetic Co²⁺ ions can be perceived as one-dimensional version of the honeycomb Kitaev model. We show that inelastic neutron scattering powder spectrum can be excellently fit with a one-dimensional extended Kitaev-Heisenberg model containing significant anisotropic bond-dependent exchange terms. This result is further supported by our state-of-the-art ab initio calculations of exchange couplings, which also show that strong Kitaev interaction in SrCoGe₂O₆ stems from substantial spin-orbit entanglement of the lowest j_eff = 1/2 doublet.