Interplay of magnetism and dimerization in the pressurized Kitaev material β-Li2IrO3

We present magnetization measurements on polycrystalline beta-Li2IrO3 under hydrostatic pressures up to 3 GPa and construct the temperature-pressure phase diagram of this material. Our data confirm that magnetic order breaks down in a first-order phase transition at p(c) approximate to 1.4 GPa and additionally reveal a steplike feature-magnetic signature of structural dimerization-that appears at p c and shifts to higher temperatures upon further compression. Following the structural study by L. S. I. Veiga et al. [Phys. RCN. B 100, 064104 (2019)], we suggest that a partially dimerized phase with a mixture of magnetic and nonmagnetic Ir4+ sites develops above p(c). This phase is thermodynamically stable between 1.7 and 2.7 GPa according to our ab initio calculations. It confines the magnetic Ir4+ sites to weakly coupled tetramers with a singlet ground state and no long-range magnetic order. Our results rule out the formation of a pressure-induced spin-liquid phase in beta-Li2IrO3 and reveal peculiarities of the magnetism collapse transition in a Kitaev material. We also show that a compressive strain imposed by the pressure treatment of beta-Li2IrO3 enhances signatures of the 100 K magnetic anomaly at ambient pressure.

Automated summary

The study investigates the magnetic behavior and dimerization features of β-Li2IrO3 under high pressures, confirming a first-order phase transition of magnetic order at 1.4 GPa. Based on first-principles calculations, a partially dimerized phase is found to be thermodynamically stable between 1.7 and 2.7 GPa.