Interplay between electronic degeneracy and crystal structure distortions in Fluoride Perovskites

Understanding the control parameters influencing orbital order (cooperative Jahn-Teller (JT) distortions) in the solid state is crucial to optimising technologically relevant properties. While oxide-based perovskites have received significant interest with extensive structural characterisation and theoretical investigations, fluoride analogues, ABF3 have comparatively under investigated. We have recently prepared ABF3 perovskites (where A = Na+, K+ and B = Mn2+, Fe2+, Co2+ and Ni2+) and propose to systematically study the low-temperature structural behaviour of key compositions to identify any orbital order (OO) driven phase transitions, bridging the gap in the literature. We will explore the interplay between crystal structure distortion, lattice strain and electronic degeneracy within the t2g orbitals. Our results will provide a broader understanding of crystal chemistry control parameters associated with the technologically relevant orbital ordering phase transitions.