High-field resonant torsion magnetometry as a probe of magnetic phases in honeycomb lattice Na₂IrO₃

We probe magnetoanisotropy of the quasi-2d honeycomb antiferromagnet Na₂IrO₃ via resonant torsion magnetometry in pulsed fields up to 65T. In recent years, this material has received much experimental and theoretical attention as a candidate for realizing Kitaev spin-liquid physics. At low temperatures, Na₂IrO₃ has a robust zigzag AFM ground state and unambiguous signatures of any field-induced transition out of this state have remained elusive so far. Our analysis of the magnetoanisotropy reveals unusual field and angular dependence at high field and a possible signature of a field-driven transition to a quantum disordered state, providing strong evidence for a potential quantum spin liquid phase at high field. We will discuss how resonant torsion magnetometry can extract detailed thermodynamic information and show how it is used to map the entire magnetic free energy in real space from data at only a handful of low symmetry angles. These results are compared to the case of related Heisenberg Kitaev material RuCl₃.