Intrinsic Ferroelectricity in Charge-Ordered Magnetite

Quantum ferroelectricity in charge-transfer complex crystals

Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure ...

Charge order in LuFe2O4: an unlikely route to ferroelectricity.

We present the refinement of the crystal structure of charge-ordered LuFe2O4, based on single-crystal x-ray diffraction data. The arrangement of the different Fe-valence states, determined with bond-valence-sum analysis, corresponds to a stacking of charged Fe bilayers, in contrast with the polar bilayers previously suggested. This arrangement is supported by an analysis of x-ray magnetic circu...

Ferroelectricity and Charge Ordering in Quasi One-Dimensional Organic Conductors

The family of molecular conductors TMTTF/TMTSF-X demonstrates almost all known electronic phases in parallel with a set of weak structural modifications of ‘anion ordering’ and mysterious ‘structureless’ transitions. Only in early 2000s their nature became elucidated by discoveries of a huge anomaly in the dielectric permittivity and by the NMR evidences for the charge ordering (disproportionat...

Charge-orbital ordering and Verwey transition in magnetite.

Local density approximation + Hubbard U (LDA + U) band structure calculations reveal that magnetite (Fe3O4) forms an insulating charge-orbital-ordered state below the Verwey transition temperature. The calculated charge ordering is in good agreement with that inferred from recent experiments. We found an associated t(2g) orbital ordering on the octahedral Fe2+ sublattice. Such an orbital orderi...

Charge-ordering in Magnetite studied by Magnetic Compton Scattering