Interplay of magnetism and dimerization in pressurized Kitaev material $\beta$-Li${}_2$IrO${}_3$

Abstract

We present magnetization measurements on polycrystalline $\beta$-Li${}_2$IrO${}_3$ 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 $p_{\mathrm{c}}$ $\approx$ 1.4~GPa and additionally reveal a step-like feature -- magnetic signature of structural dimerization -- that appears at $p_{\mathrm{c}}$ 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 Ir${}^{4+}$ sites develops above $p_{\mathrm{c}}$. This phase is thermodynamically stable between 1.7 and 2.7~GPa according to our ab initio calculations. It confines the magnetic Ir${}^{4+}$ 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 $\beta$-Li${}_2$IrO${}_3$ 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 $\beta$-Li${}_2$IrO${}_3$ enhances signatures of the 100~K magnetic anomaly at ambient pressure.

10 pages, 10 figures

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Cited by in corpus (1)

• Monoclinic distortion in hyperhoneycomb Kitaev material $\beta$-ZnIrO${}_3$ revealed by improved sample quality