Novel magnetism on a honeycomb lattice in a-RuCl3 studied by muon spin rotation

TL;DR

This study uses muon spin rotation to investigate magnetic phases in a-RuCl3, revealing two phase transitions and confirming a zig-zag antiferromagnetic order consistent with theoretical models.

Contribution

It provides experimental evidence of magnetic phase transitions and confirms the magnetic structure in a-RuCl3 using muon spin rotation and theoretical calculations.

Findings

Two phase transitions at 11 K and 14 K identified.

Muon sites consistent with zig-zag antiferromagnetic order.

Experimental data supports theoretical magnetic structure.

Abstract

Muon spin rotation measurements have been performed on a powder sample of a-RuCl3, a layered material which previously has been proposed to be a quantum magnet on a honeycomb lattice close to a quantum spin liquid ground state. Our data reveal two distinct phase transitions at 11 K and 14 K which we interpret as originating from the onset of three-dimensional order and in-plane magnetic order, respectively. We identify, with the help of density functional theory calculations, likely muon stopping sites and combine these with dipolar field calculations to show that the two measured muon rotation frequencies are consistent with two inequivalent muon sites within a zig-zag antiferromagnetic structure proposed previously.