Ground state magnetic phase in single-crystal and magnon spectrum in polycrystalline honeycomb Na₂Ni₂TeO₆

The honeycomb arrangement of Ni²⁺ moments in Na₂Ni₂TeO₆ has generated interest in its potential to harbor Kitaev interactions that may hint at new quantum spin liquid candidate materials. Various neutron diffraction studies on polycrystalline materials have resulted in conflicting reports for its ground state magnetic order, ranging from incommensurate (0.47, 0.44,0.28) to differing commensurate orders (1/2,0,0), (1/2,0,1/2), or (1/2,1/2,1/2) or multiple of these coexisting. We have successfully prepared single crystal specimen of Na₂Ni₂TeO₆ using the flux growth method and have performed single crystal neutron diffraction in order to add new insight into the ground state ordering. Our results point to a single commensurate wave vector but with moments aligned within the plane. To better understand the role of Kitaev interaction in the system we have also performed inelastic neutron spectroscopy on powder samples in zero and applied field. The spin dynamics will be discussed in the context of the ground state ordering.