‘Molecular-like’ Ordering in the Solid State
Our research in this area involves understanding the often complex crystal structures that arise as a result of phase transitions due to electronic ordering phenomena. The complexity of the resulting structures is often due to the competition between local (ion centred) and global (lattice) degrees of freedom.
In magnetite Fe+3Fe+2.52O4 we have shown that charge ordering (ion centred) in the low temperature (Verwey) phase is only stabilised by a complex orbital ordering involving three site distortions.[1, 2] This cooperative ‘Molecular-like’ ordering is also found to explain the unusual near integer charge ordering of Ru5.5+ to Ru5+ and Ru6+in Ru2O9 dimers of Ba3NaRu2O9.
Investigating how molecular like interactions may stabilise unusual forms of charge ordering remains an active area of research.