Unveiling the ambient-condition structure of Sr ₂ FeIrO ₆ : a triclinic phase through synchrotron-based X-ray techniques and high pressure

Double perovskites with the formula A ₂ BB ′O ₆ , such as Sr ₂ FeIrO ₆ , are being explored as unique platforms for unveiling diverse structural, electronic and magnetic properties. Inclusion of 3 d and 5 d transition metals in the B and B ′ sites, as in Sr ₂ FeIrO ₆ , enables the study of electron correlation and spin–orbit coupling effects to tailor promising properties. The structure of Sr ₂ FeIrO ₆ under ambient conditions has been widely debated, with theoretical and experimental studies suggesting several potential structures. This uncertainty complicates the understanding of its magnetic and electronic behaviours. High-pressure X-ray diffraction measurements, complemented by high-resolution powder X-ray diffraction studies under ambient conditions, have provided a definitive structural characterization of Sr ₂ FeIrO ₆ , crucial for interpreting its properties and guiding future research.