Effects of Non-Stoichiometry on the Ground State of the Frustrated System LiNiSbO.

The non-stoichiometric system LiNiSbO is a Li-deficient derivative of the zigzag honeycomb antiferromagnet LiNiSbO. Structural and magnetic properties of LiNiSbO were studied by means of X-ray diffraction, magnetic susceptibility, specific heat, and nuclear magnetic resonance measurements. Powder X-ray diffraction data shows the formation of a new phase, which is Sb-enriched and Li-deficient with respect to the structurally honeycomb-ordered LiNiSbO. This structural modification manifests in a drastic change of the magnetic properties in comparison to the stoichiometric partner. Bulk static (dc) magnetic susceptibility measurements show an overall antiferromagnetic interaction ( = -4 K) between Ni spins ( = 1), while dynamic (ac) susceptibility reveals a transition into a spin glass state at a freezing temperature ~ 8 K. These results were supported by the absence of the λ-anomaly in the specific heat (T) down to 2 K. Moreover, combination of the bulk static susceptibility, heat capacity and Li NMR studies indicates a complicated temperature transformation of the magnetic system. We observe a development of a cluster spin glass, where the Ising-like Ni magnetic moments demonstrate a 2D correlated slow short-range dynamics already at 12 K, whereas the formation of 3D short range static ordered clusters occurs far below the spin-glass freezing temperature at T ~ 4 K as it can be seen from the Li NMR spectrum.