Chemical- and hydrostatic-pressure effects on the Kitaev honeycomb material Na$_2$IrO$_3$

TL;DR

This study investigates how chemical substitution and hydrostatic pressure influence the magnetic properties of Na$_2$IrO$_3$, revealing disorder effects and enhanced magnetic ordering temperatures, which are relevant for understanding quantum spin liquids.

Contribution

It provides new insights into how chemical and hydrostatic pressures affect magnetic order and interactions in Na$_2$IrO$_3$, a candidate quantum spin-liquid material.

Findings

Li substitution causes inhomogeneous magnetic order

Hydrostatic pressure increases the magnetic ordering temperature

Pressure enhances three-dimensional magnetic interactions

Abstract

The low-temperature magnetic properties of \tcr{polycrystalline} Na$_2$IrO$_3$, a candidate material for the realization of a quantum spin-liquid state, were investigated by means of muon-spin relaxation and nuclear magnetic resonance methods under chemical and hydrostatic pressure. The Li-for-Na chemical substitution promotes an inhomogeneous magnetic order, whereas hydrostatic pressure (up to 3.9\,GPa) results in an enhancement of the ordering temperature $T_\mathrm{N}$. In the first case, the inhomogeneous magnetic order suggests either short- or long-range correlations of broadly distributed $j=\,$\textonehalf\ Ir$^{4+}$ magnetic moments, reflecting local disorder. The increase of $T_\mathrm{N}$ under applied pressure points at an increased strength of three dimensional interactions arising from interlayer compression.