Magnetic properties of the honeycomb oxide Na$_2$Co$_2$TeO$_6$

TL;DR

This study investigates the magnetic properties of Na$_2$Co$_2$TeO$_6$, revealing a zig-zag antiferromagnetic order with unusual spatial correlations, supported by neutron diffraction and Monte Carlo modeling.

Contribution

It provides the first detailed analysis of magnetic ordering and correlations in Na$_2$Co$_2$TeO$_6$, combining experimental and theoretical approaches.

Findings

Identified zig-zag antiferromagnetic order in Na$_2$Co$_2$TeO$_6$

Discovered peculiar spatial magnetic correlations unaffected by temperature

Monte Carlo model reproduces neutron diffraction data

Abstract

We have studied the magnetic properties of Na$_2$Co$_2$TeO$_6$, which features a honeycomb lattice of magnetic Co$^{2+}$ ions, through macroscopic characterization and neutron diffraction on a powder sample. We have shown that this material orders in a zig-zag antiferromagnetic structure. In addition to allowing a linear magnetoelectric coupling, this magnetic arrangement displays very peculiar spatial magnetic correlations, larger in the honeycomb planes than between the planes, which do not evolve with the temperature. We have investigated this behavior by Monte Carlo calculations using the $J_1$-$J_2$-$J_3$ model on a honeycomb lattice with a small interplane interaction. Our model reproduces the experimental neutron structure factor, although its absence of temperature evolution must be due to additional ingredients, such as chemical disorder or quantum fluctuations enhanced by the proximity to a phase boundary.