Counterrotating magnetic order in the honeycomb layers of NaNi2BiO6−δ

The exotic Kitaev spin liquid state emerges from a particular form of anisotropic magnetic exchange on the honeycomb lattice. Here, the authors use neutron scattering, electron spin resonance, and density functional theory to show that bond-anisotropic Kitaev exchange exists in between Ni${}³⁺$ ions in the honeycomb layers of NaNi${}₂$BiO${}_5.66$. This magnetic exchange produces a complex counterrotating low-temperature magnetic order with 120\ifmmode^\circ\else\textdegree\fi{} in-plane order in this compound. These results demonstrate that Kitaev physics can be found in 3$d$ transition ion materials.