A combination of x-ray absorption, x-ray-diffraction, and transport measurements at high pressure is used to investigate the interplay between the electronic properties of Ir 5⁢𝑑 states and lattice degrees of freedom in the weakly ferromagnetic insulator BaIrO3. Although the Ir 5⁢𝑑 local magnetic moment is highly stable against lattice compression, remaining nearly unperturbed to at least 30 GPa, the weak ferromagnetism (net ordered moment) is quickly quenched by 4.5 GPa (3% volume reduction). Under chemical pressure, where Sr is substituted for the larger Ba in BaIrO3, the local magnetic moment on Ir remains stable, but the weak ferromagnetism is quenched after only 1.7% volume reduction. The magnetic ordering temperature 𝑇𝑚 is also more strongly suppressed by chemical pressure compared to physical pressure. In addition, under ∼23−at.% Sr doping, BaIrO3 undergoes a transition to a paramagnetic metallic state. Resistivity measurements indicate that BaIrO3 remains an electrical insulator to at least 9 GPa, a much higher pressure than required to quench the weak ferromagnetism (∼4.5GPa). Such a disparate response of transport and magnetic properties to chemical and physical pressure is likely rooted in the different compression rates of the (𝑎,𝑐) lattice parameters with Sr doping and applied pressure and the effect of related lattice distortions on electronic bandwidth and exchange interactions in this strongly spin-orbit-coupled system.

Work at Argonne is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC-02-06CH11357. M. A. Laguna-Marco acknowledges Spanish MICINN for a postdoctoral grant and CSIC for a JAE-Doc contract. Research at Washington University was supported by the National Science Foundation (NSF) through Grant No. DMR-1104742 and by the Carnegie/DOE Alliance Center (CDAC) through NNSA/DOE Grant No. DE-FC52- 08NA28554. Work at the University of Kentucky was supported by the NSF through Grant No. DMR-1265162.

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