Correlation between ferroelectricity and electronic density of states near the Fermi level in BaTiO 3
Abstract The electronic density of states in BaTiO 3 is studied by means of X‐ray absorption near‐edge structure in a vicinity of a Ti K edge and Ba L edges. A 4pπ band of the Ti ion and a 5dπ band of the Ba ion having a high‐density unoccupied state occupy a level just above the Fermi level ( E F )...
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Published in | physica status solidi (b) Vol. 241; no. 5; pp. 1058 - 1065 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
01.04.2004
|
Online Access | Get full text |
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Summary: | Abstract
The electronic density of states in BaTiO
3
is studied by means of X‐ray absorption near‐edge structure in a vicinity of a Ti K edge and Ba L edges. A 4pπ band of the Ti ion and a 5dπ band of the Ba ion having a high‐density unoccupied state occupy a level just above the Fermi level (
E
F
). The pre‐edge peaks give that, in addition to an O
2−
2p valence band, the electronic density of states below
E
F
are composed of negative‐charge‐transfer bands 3d
1
, 3d
1
$ \underline {\rm L} $
and 3d
2
$ \underline {\rm L} $
2
of Ti ions and 4f
1
, 4f
1
$ \underline {\rm L} $
and 4f
2
$ \underline {\rm L} $
2
of Ba ions. The 3d
1
, 3d
1
$ \underline {\rm L} $
and 3d
2
$ \underline {\rm L} $
2
bands of Ti ions gives that a mixture of the different oxidation states Ti
2+
and Ti
3+
is present in addition to Ti
4+
. The 4f
1
, 4f
1
$ \underline {\rm L} $
and 4f
2
$ \underline {\rm L} $
2
bands are induced by a hybridization between Ba
2+
4d and O
2–
2p orbitals via an electronic configuration interaction between the 4f and 4d orbitals of the Ba ion. The disappearance of the 4f
1
, 4f
1
$ \underline {\rm L} $
and 4f
2
$ \underline {\rm L} $
2
bands in the ferroelectric phase suggests that the collective displacement of Ba ions from ideal ionic sites of the cubic perovskite‐type structure reduces the hybridization between the Ba and O ions. This gives that the effective charge on the O ions is increased and induces a large dipole moment between the O ions and the Ti ions, which are at an off‐center position of TiO
6
octahedra in the ferroelectric phase. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) |
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ISSN: | 0370-1972 1521-3951 |
DOI: | 10.1002/pssb.200301981 |