Structure transition and zigzag magnetic order in Ir/Rh-substituted honeycomb lattice RuCl3

TL;DR

This study investigates how Ir and Rh substitution in honeycomb lattice RuCl3 affects its structural phase transition and magnetic order, revealing a persistent zigzag magnetic order with reduced magnetic moments, offering insights into quantum spin liquid behavior.

Contribution

It provides detailed magnetic and structural characterization of Ir- and Rh-substituted RuCl3, highlighting changes in magnetic moments and canting angles compared to the parent compound.

Findings

Zigzag magnetic order persists after substitution.

Magnetic moments are reduced in substituted samples.

Structural phase transition exhibits large hysteresis.

Abstract

We report magnetization and neutron diffraction studies on crystal and magnetic structures of Ir- and Rh-substituted honeycomb lattice $\alpha$-RuCl$_3$. The iridium or rhodium atoms are distributed at the Ru site with little structural modification. Both systems undergo a room-temperature monoclinic $C2/m$ to low-temperature trigonal $R\bar{3}$ phase transformation with a large recoverable hysteresis. At low temperature, a zigzag spin order is observed with the same characteristic wavevector $(0,0.5,1)$ as in the parent $\alpha$-RuCl$_3$. Detailed magnetic structure refinement reveals an ordered moment of $\rm 0.32(5) \mu_B/Ru$ and a upper boundary of canting angle of $15(4)^\circ$ away from the basal plane at 5~K for the 10\% Ir-substituted $\alpha$-RuCl$_3$, which is different from the 0.45-0.73~$\rm \mu_B/Ru$ and $32^\circ$-$48^\circ$ canting angle reported in the parent compound $\alpha$-RuCl$_3$. The observation of unchanged RuCl$_6$ local octahedral environment, reduced magnetic moment size and canting angle highlights the potential to study quantum spin liquid behavior through non-magnetic ion doping.