We present magnetization measurements on polycrystalline β-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 pc≈ 1.4~GPa and additionally reveal a step-like feature -- magnetic signature of structural dimerization -- that appears at pc and shifts to higher temperatures upon further compression. Following the structural study by L. S. I. Veiga et al. [Phys. Rev. B 100, 064104 (2019)], we suggest that a partially dimerized phase with a mixture of magnetic and non-magnetic Ir4+ sites develops above pc. 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 β-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 β-Li2IrO3 enhances signatures of the 100~K magnetic anomaly at ambient pressure.
@article{arxiv.2108.03118,
title = {Interplay of magnetism and dimerization in pressurized Kitaev material $\beta$-Li$_2$IrO$_3$},
author = {Bin Shen and Anton Jesche and Maximilian L. Seidler and Friedrich Freund and Philipp Gegenwart and Alexander A. Tsirlin},
journal= {arXiv preprint arXiv:2108.03118},
year = {2021}
}