Hybrid Improper Ferroelectricity in Columnar (NaY)MnMnTi4O12

We show that cation ordering on A site columns, oppositely displaced via coupling to B site octahedral tilts, results in a polar phase of the columnar perovskite (NaY)MnMnTi4O12. This scheme is similar to hybrid improper ferroelectricity found in layered perovskites, and can be considered a realisation of hybrid improper ferroelectricity in columnar perovskites. The cation ordering is controlled by annealing temperature and when present it also polarises the local dipoles associated with pseudo-Jahn-Teller active Mn2+ ions to establish an additional ferroelectric order out of an otherwise disordered dipolar glass. Below T-N approximate to 12 K, Mn2+ spins order, making the columnar perovskites rare systems in which ordered electric and magnetic dipoles may reside on the same transition metal sublattice.

Automated summary

We demonstrate a polar phase in the columnar perovskite (NaY)MnMnTi4O12, resulting from cation ordering on A site columns, which are oppositely displaced through coupling to B site octahedral tilts. This ordering, controlled by annealing temperature, also polarizes the local dipoles associated with pseudo-Jahn-Teller active Mn2+ ions, generating an additional ferroelectric order. Below T-N approximately 12 K, Mn2+ spins order, making this system rare in having ordered electric and magnetic dipoles on the same transition metal sublattice.