Local spin structure of the $\alpha$-RuCl${}_3$ honeycomb-lattice magnet observed via muon spin rotation/relaxation

Abstract

We report a muon spin rotation/relaxation ($\mu$SR) study of single-crystalline samples of the $\alpha$-RuCl${}_3$ honeycomb magnet, which is presumed to be a model compound for the Kitaev-Heisenberg interaction. It is inferred from magnetic susceptibility and specific-heat measurements that the present samples exhibit successive magnetic transitions at different critical temperatures $T_{\mathrm{N}}$ with decreasing temperature, eventually falling into the $T_{\mathrm{N}}=7$ K antiferromagnetic (7 K) phase that has been observed in only single-crystalline specimens with the least stacking fault. Via $\mu$SR measurements conducted under a zero external field, we show that such behavior originates from a phase separation induced by the honeycomb plane stacking fault, yielding multiple domains with different $T_{\mathrm{N}}$'s. We also perform $\mu$SR measurements under a transverse field in the paramagnetic phase to identify the muon site from the muon-Ru hyperfine parameters. Based on a comparison of the experimental and calculated internal fields at the muon site for the two possible spin structures inferred from neutron diffraction data, we suggest a modulated zig-zag spin structure for the 7 K phase, with the amplitude of the ordered magnetic moment being significantly reduced from that expected for the orbital quenched spin-1/2 state.

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• Rethinking $\alpha$-RuCl${}_3$
• Kitaev honeycomb models in magnetic fields: Dynamical response and hidden symmetries
• Competing Antiferromagnetic-Ferromagnetic States in $d^7$ Kitaev Honeycomb Magnet
• Anderson-Kitaev spin liquid
• Unusual spin dynamics in the low-temperature magnetically ordered state of Ag${}_3$LiIr${}_2$O${}_6$
• Polaronic Conductivity in Cr${}_2$Ge${}_2$Te${}_6$ Single Crystals
• Persistent spin dynamics in magnetically ordered honeycomb cobalt oxides
• Magnetism in Kitaev Quantum Spin Liquid Candidate RuBr${}_3$
• Anomalous ferromagnetic behavior in the orthorhombic Li${}_3$Co${}_2$SbO${}_6$
• Coupled spin-1/2 antiferromagnetic chain Cs${}_2$LiRuCl${}_6$ with partially disordered crystal lattice