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Regular version of the site

Article

Incipient multiferroicity in Pnma fluoroperovskite NaMnF3

Physical Review B: Condensed Matter and Materials Physics. 2020. Vol. 101. P. 180403-1-180403-6.
Dubrovin R., Alyabyeva L., Siverin N., Gorshunov B., Novikova N., Boldyrev K., Pisarev R.

Recent theoretical studies predict the suppressed ferroelectric instability in orthorhombic Pnma perovskites
and experimental evidence is due. We observed significant softening at cooling of the lowest-frequency polar
phonon at the Brillouin zone center in the Pnma antiferromagnetic fluoroperovskite NaMnF3 that is the direct
proof of the theoretically predicted ferroelectric instability. In contrast to oxides where the hybridization plays
the dominant role, the effective ionic charges in fluoroperovskites are close to their nominal valencies that
confirms the geometric origin of the observed incipient ferroelectricity. Furthermore, below the Néel temperature,
the softening phonon clearly shows a strong coupling with the magnetic subsystem as a result of dynamical
modulation of the superexchange interaction. Our findings clarify microscopic mechanisms of the incipient
multiferroicity in the Pnma fluoroperovskites and reveal still unexplored opportunities of this class of materials
for further research and potential applications.