Magnetic Structure, Excitations and Short-Range order in Honeycomb Na2Ni2TeO6

Published

July 15, 2021

Author(s)

Nathan Episcopo, Po-Hao Chang, Thomas W. Heitmann, Kinley Wangmo, James M. Guthrie, Magdalena Fitta, Ryan Klein, Narayan Poudel, Krzysztof Gofryk, Rajendra R. Zope, Craig Brown, Harikrishnan S. Nair

Abstract

Na₂Ni₂TeO₆ has a layered hexagonal structure with a honeycomb lattice constituted by Ni²⁺ and a chiral charge distribution of Na⁺ that resides between the Ni layers. In the present work, the antiferromagnetic transition temperature of Na₂Ni₂TeO₆ is confirmed at T_Napproximately equal}27 K, and further, it is found to be robust up to 8 T magnetic field and 1.2 GPa external pressure; and, without any frequency-dependence. Our analysis of neutron diffraction data shows that the magnetic structure of Na₂Ni₂TeO₆is faithfully described by a model consisting of two phases described by the commensurate wave vectors k_c, (0:5 0 0) and (0:5 0 0:5), with an additional short-range order component incorporated in to the latter phase. Comparable, but slightly quantitatively poorer refinement results are obtained by using a commensurate wave vector (0:5 0 0) together with the proposed incommensurate k_ic, (0:47 0:44 0:28). Consequently, a zig-zag long-range ordered magnetic phase of Ni²⁺ results in the compound, mixed with a short-range ordered phase. Theoretical computations based on density functional theory predict predominantly in-plane magnetic exchange interactions that conform to a J₁-J₂-J₃ model with a strong J₃ term. The computationally predicted parameters lead to a reliable estimate for T_N and the experimentally observed zig-zag magnetic structure. A spin wave excitation in Na₂Ni₂TeO₆ at Eapproximately equal} 5 meV at T = 5 K is mapped out through inelastic neutron scattering experiments, which is reproduced by linear spin wave theory calculations using the J values from our computations.

Citation

Journal of Physics: Condensed Matter

Volume

33

Issue

37

Pub Type

Journals

Citation

Episcopo, N. , Chang, P. , Heitmann, T. , Wangmo, K. , Guthrie, J. , Fitta, M. , Klein, R. , Poudel, N. , Gofryk, K. , Zope, R. , Brown, C. and Nair, H. (2021), Magnetic Structure, Excitations and Short-Range order in Honeycomb Na₂Ni₂TeO₆, Journal of Physics: Condensed Matter (Accessed April 20, 2024)