Mott insulating low thermal expansion perovskite TiF3

Artikel i vetenskaplig tidskrift, 2023

We characterize perovskite TiF3, a material which is reported to display significant negative thermal expansion at elevated temperatures above its cubic-to-rhombohedral structural phase transition at 330 K. We find the optical response favors an insulating state in both structural phases, which we show can be produced in density functional theory calculations only through the introduction of an on-site Coulomb repulsion. Analysis of the magnetic susceptibility data gives a S=12 local moment per Ti+3 ion and an antiferromagnetic exchange coupling. Together, these results show that TiF3 is a strongly correlated electron system, a fact which constrains possible mechanisms of strong negative thermal expansion in the Sc1-xTixF3 system. We consider the relative strength of the Jahn-Teller and electric dipole interactions in driving the structural transition.