A Study of the Frustrated Honeycomb Battery Material NA2NI2TEO6

The P2-type layered hexagonal compound Na2Ni2TeO6 with Ni2+ on a honeycomb lattice was synthesized by the standard solid-state route. Structural characterization chemical phase purity was confirmed by Rietveld refinement of laboratory and synchrotron data. The crystal structure refines well in the P63/mcm space group. Single crystal growth trials using the self-flux-melt method were conducted with limited success. The magnetic transition temperature pertaining to Ni2+ lattice was confirmed by analysis of specific heat capacity to be TN = 27 K . The magnetic susceptibility remains largely unchanged in magnetic field of H = 80 k0e and external pressure of P = 1.2 GPa. There is an almost linear response in isothermal magnetization up to H = 130 k0e. The nuclear structure studied using high resolution neutron diffraction data confirms the results from refinement of synchrotron data. Four different magnetic structure models were used to quantitatively analyze T = 5 K neutron diffraction data, with the best fitting model consisting of two commiserate propagation vectors K→c = (0.500) and K→c = (0.5005) and with an additional profile term to account for short-range ordering. The long-range magnetic structure produced by the multi-phase model consist of 2D in-plane (ab) zig-zag ferromagnetic chains and are antiferromagnetically arranged in adjacent chains. Inelastic neutron scattering shows Na2Ni2TeO6 has a spin wave excitation with energy E ≈ 5meV at T = 5