Susceptibility anisotropy and absence of ferroelectric order in the Kitaev spin liquid candidate Na$_2$Co$_2$TeO$_6$

TL;DR

This study investigates the magnetic and dielectric properties of Na₂Co₂TeO₆, a candidate Kitaev spin liquid, revealing strong anisotropy, absence of ferroelectric order, and insights into its magnetic structure.

Contribution

The paper provides experimental evidence of anisotropic magnetic behavior and confirms the lack of electric polarization, clarifying the magnetic structure and magnetoelectric properties of Na₂Co₂TeO₆.

Findings

Strong magnetic anisotropy observed in susceptibility.

No finite electric polarization below 100 K.

Supports zig-zag AFM structure over triple-Q in NCTO.

Abstract

We report the magnetic, magnetodielectric, and electric polarization properties of single crystals of the Co-based Kitaev Spin Liquid (KSL) candidate Na$_2$Co$_2$TeO$_6$ (NCTO). The sample shows magnetic transitions at 26 K, 16 K, and 5 K, consistent with the literature. The magnetic measurements along and perpendicular to the Co-honeycomb planes show a strong anisotropy in susceptibility and in Curie-Weiss (C-W) temperatures. The experimental anisotropic C-W temperatures of NCTO qualitatively match with the theoretical C-W temperatures, calculated using the HKTF model [C. Kim \textit{et al.}, J. Phys.: Condens. Matter \textbf{34}, 045802 (2021)]. We find from our temperature- and field-dependent dielectric and pyroelectric ($I_p$) current studies ($H\parallel ab$ and $E\perp ab$) that our single crystal NCTO samples do not have a finite electric polarization below 100 K. These $I_p$ studies confirm the absence of a magnetoelectric coupling and electric polarization properties in the title compound and suggest that the zig-zag AFM structure is more favorable than the triple-$Q$ structure with AFM Kitaev interactions.