High-pressure stabilization of Mg2IrH7: Structural proximity to high-Tc superconductivity

TL;DR

This study investigates the high-pressure stabilization of Mg₂IrH₇, revealing its structure, insulating nature, and potential pathways to synthesize superconducting Mg₂IrH₆, with implications for high-temperature superconductivity in hydrides.

Contribution

The paper provides experimental validation of predicted structures in the Mg-Ir-H system and demonstrates the stabilization of Mg₂IrH₇ at high pressures, opening new avenues for superconductivity research.

Findings

Mg₂IrH₇ is stabilized above 40 GPa.

Mg₂IrH₇ is insulating at high pressure.

Reverts to Mg₂IrH₅ below 20 GPa.

Abstract

Mg$_2$IrH$_6$ is a metastable complex metal hydride with a predicted superconducting transition temperature as high as 170 K at ambient pressure. Following the synthesis of isomorphic, insulating Mg$_2$IrH$_5$ at low pressure, higher-pressure studies were conducted to investigate the phase behavior and compound formation in this system. X-ray diffraction and Raman spectroscopic measurements indicate that cubic Mg$_2$IrH$_7$ is stabilized above ca. 40 GPa and coexists with a related hexagonal hydride with likely composition near Mg$_2$IrH$_5$. Electrical transport measurements show that the cubic Mg$_2$IrH$_7$ is insulating, in agreement with ab initio predictions, and persists during room-temperature decompression until $\sim$20 GPa before reverting back to the cubic Mg$_2$IrH$_5$. The experimental results confirm ground-state structure predictions in the Mg-Ir-H system, and the formation of two nearly identical phases with surrounding compositions opens new opportunities to access superconducting Mg$_2$IrH$_6$ through non-equilibrium processing pathways.