Fragile magnetic order in the honeycomb lattice Iridate Na$_{2}$IrO$_3$ revealed by magnetic impurity doping

TL;DR

This study investigates how substituting Ru into Na₂IrO₃ affects its magnetic properties, revealing that the magnetic order is highly fragile and easily disrupted, highlighting the importance of nearest-neighbor exchange interactions.

Contribution

It demonstrates that magnetic order in Na₂IrO₃ is extremely fragile and can be suppressed by minimal Ru doping, emphasizing the role of nearest-neighbor exchange in this material.

Findings

Ru doping induces spin glass behavior instead of magnetic order

Magnetic order in Na₂IrO₃ is highly sensitive to impurities

All samples remain insulating despite doping

Abstract

We report the structure, magnetic, and thermal property measurements on single crystalline and polycrystalline samples of Ru substituted honeycomb lattice iridate Na$_2$Ir$_x$Ru$_{1-x}$O$_3$ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5). The evolution of magnetism in Na$_2$Ir$_x$Ru$_{1-x}$O$_3$ has been studied using dc and ac magnetic susceptibility, and heat capacity measurements. The parent compound Na$_2$IrO$_3$ is a spin-orbit driven Mott insulator with magnetic order of reduced moments below $T_N = 15$~K\@. In the Ru substituted samples the antiferromagnetic long range state is replaced by a spin glass like state even for the smallest substitution suggesting that the magnetic order in Na$_2$IrO$_3$ is extremely fragile. We argue that these behaviors indicate the importance of nearest-neighbor magnetic exchange in the parent Na$_2$IrO$_3$. Additionally, all samples show insulating electrical transport.