Local structure study of orbital order-disorder transition in ACrF3 and ACuF3 (A = Ag, Na, K, Rb, Cs and NH4) fluoroperovskites

ACrF3 and ACuF3 (A = Ag, Na, K, Rb, Cs and NH4) have Jahn-Teller active electron configurations and as a consequence, the crystal structures are distorted. The crystal structure is triclinic form small A-site cations (Ag and Na) and tetragonal for large A-site cations (K, Rb, Cs and NH4). Upon heating, the orbital ordering melts into a distordered state with higher symmetry. The proposed experiment aims to study the local structure in ACrF3 and ACuF3 over the order-disorder transition by pair distribution functions (PDFs) and x-ray absorption spectroscopy (XAS). The experiment will address the nature of the transition and give insight to electronic and magnetic isotropy present in the compounds.