Chemical and hydrostatic-pressure effects on the Kitaev honeycomb material Na2IrO3

Abstract

The low-temperature magnetic properties of polycrystalline Na2IrO3, 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 TN. In the first case, the inhomogeneous magnetic order suggests either short- or long-range correlations of broadly distributed j=½ Ir4+ magnetic moments, reflecting local disorder. The increase of TN under applied pressure points at an increased strength of three-dimensional interactions arising from interlayer compression.