Magnetism of two-dimensional honeycomb layered Na₂ Ni₂ TeO₆ driven by intermediate Na-layer crystal structure

Abstract

The microscopic spin-spin correlations in the two-dimensional (2D) layered spin-1 honeycomb lattice compound Na₂ Ni₂ TeO₆ have been investigated by neutron diffraction and inelastic neutron scattering (INS). In this paper, we reveal a magnetic phenomenon where the magnetic symmetry is controlled by the nonmagnetic Na layer, which is a unique feature for the studied compound Na₂ Ni₂ TeO₆ with respect to other Na-based layered compounds, especially A₂M₂XO₆ or A₃M₂XO₆ compounds. The honeycomb lattice of spin-1 Ni2+ ions, within the crystallographic a b planes, are well separated (∼ 5.6 Å) along the c axis by an intermediate Na layer whose crystal structure contains chiral nuclear density distributions of Na ions. The chirality of the alternating Na layers is opposite.