Collective phase-like mode and the role of lattice distortions at T sub(N) ~ T sub(C) in RMn sub(2)O sub(5) (R = Pr, Sm, Gd, Tb, Bi)

We report on electronic collective excitations in RMn sub(2)O sub(5) (R = Pr, Sm, Gd, Tb) showing condensation starting at and below ~T sub(N) ~ T sub(C) ~ 40-50 K. Their origin is understood as partial delocalized e sub(g) electron orbitals in the Jahn-Teller distortion of the pyramid dimer with st...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2012-05, Vol.24 (19), p.1-10
Main Authors: Massa, Nestor E, Garcia-Flores, Ali F, De Sousa Meneses, Domingos, del Campo, Leire, Echegut, Patrick, Fabbris, Gilberto F L, Martinez-Lope, Maria Jesus, Alonso, Jose Antonio
Format: Article
Language:English
Subjects:
Condensed matter
Distortion
Electron orbitals
Electronics
Lattices
Nuclei
Position (location)
Rare earth metals
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Summary:We report on electronic collective excitations in RMn sub(2)O sub(5) (R = Pr, Sm, Gd, Tb) showing condensation starting at and below ~T sub(N) ~ T sub(C) ~ 40-50 K. Their origin is understood as partial delocalized e sub(g) electron orbitals in the Jahn-Teller distortion of the pyramid dimer with strong hybridized Mn super(3+)-O bonds. Our local probes, Raman, infrared, and x-ray absorption, back the conclusion that there is no structural phase transition at T sub(N) ~ T sub(C). Ferroelectricity is magnetically assisted by electron localization triggering lattice polarizability by unscreening. We have also found phonon hardening as the rare earth is sequentially replaced. This is understood as a consequence of lanthanide contraction. It is suggested that partially f-electron screened rare earth nuclei might be introducing a perturbation to e sub(g) electrons prone to delocalize as the superexchange interaction takes place.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/24/19/195901