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Ferroelectric-like metallic state in electron doped BaTiO3.

Fujioka J, Doi A, Okuyama D, Morikawa D, Arima T, Okada KN, Kaneko Y, Fukuda T, Uchiyama H, Ishikawa D, Baron AQ, Kato K, Takata M, Tokura Y - Sci Rep (2015)

Bottom Line: We report that a ferroelectric-like metallic state with reduced anisotropy of polarization is created by the doping of conduction electrons into BaTiO3, on the bases of x-ray/electron diffraction and infrared spectroscopic experiments.The crystal structure is heterogeneous in nanometer-scale, as enabled by the reduced polarization anisotropy.The enhanced infrared intensity of soft phonon along with the resistivity reduction suggests the presence of unusual electron-phonon coupling, which may be responsible for the emergent ferroelectric structure compatible with metallic state.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Hongo, Tokyo 113-8656, Japan.

ABSTRACT
We report that a ferroelectric-like metallic state with reduced anisotropy of polarization is created by the doping of conduction electrons into BaTiO3, on the bases of x-ray/electron diffraction and infrared spectroscopic experiments. The crystal structure is heterogeneous in nanometer-scale, as enabled by the reduced polarization anisotropy. The enhanced infrared intensity of soft phonon along with the resistivity reduction suggests the presence of unusual electron-phonon coupling, which may be responsible for the emergent ferroelectric structure compatible with metallic state.

No MeSH data available.


The patterns of convergent beam electron diffraction for the incident beams.(a) along [001] and (b) [100] axes at 290 K (tetragonal phase). The symmetries are 4mm and m, respectively. X-ray oscillation photographs around (009) reflection at (c) 270 K and (d) 20 K. The red dotted and black dashed lines denote the [001],  and  axis, respectively. The color-scale bar at right side of figure denotes the diffraction intensity in arbitrary units.
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f3: The patterns of convergent beam electron diffraction for the incident beams.(a) along [001] and (b) [100] axes at 290 K (tetragonal phase). The symmetries are 4mm and m, respectively. X-ray oscillation photographs around (009) reflection at (c) 270 K and (d) 20 K. The red dotted and black dashed lines denote the [001], and axis, respectively. The color-scale bar at right side of figure denotes the diffraction intensity in arbitrary units.

Mentions: Figure 3(a) shows the zeroth-order Laue zone reflections of the CBED pattern taken at 290 K. The CBED pattern with the incident beam parallel to [001] axis exhibits the symmetry, that is, a 4-fold rotation symmetry around [001] axis and two mirror symmetries respectively perpendicular to [100] and [110] directions. Conversely, as exemplified in Fig. 3(b), the CBED pattern with the incident beam parallel to [100] axis does not exhibit a mirror symmetry perpendicular to [001] axis, while a mirror symmetry perpendicular to [010] axis is maintained. This is not consistent with the centrosymmetric P4/mmm symmetry, but rather agrees with the noncentrosymmetric P4mm structure, which is compatible with the presence of polar axis (electric polarization) along [001] direction. Given the polar crystallographic symmetry, we refined the single crystalline synchrotron x-ray diffractogram and analyzed the crystal structure with reliability factors R = 2.10% and Rwp = 2.49% (Supplemental Information 1). The detail of structural parameters are listed in Table 1.


Ferroelectric-like metallic state in electron doped BaTiO3.

Fujioka J, Doi A, Okuyama D, Morikawa D, Arima T, Okada KN, Kaneko Y, Fukuda T, Uchiyama H, Ishikawa D, Baron AQ, Kato K, Takata M, Tokura Y - Sci Rep (2015)

The patterns of convergent beam electron diffraction for the incident beams.(a) along [001] and (b) [100] axes at 290 K (tetragonal phase). The symmetries are 4mm and m, respectively. X-ray oscillation photographs around (009) reflection at (c) 270 K and (d) 20 K. The red dotted and black dashed lines denote the [001],  and  axis, respectively. The color-scale bar at right side of figure denotes the diffraction intensity in arbitrary units.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4542543&req=5

f3: The patterns of convergent beam electron diffraction for the incident beams.(a) along [001] and (b) [100] axes at 290 K (tetragonal phase). The symmetries are 4mm and m, respectively. X-ray oscillation photographs around (009) reflection at (c) 270 K and (d) 20 K. The red dotted and black dashed lines denote the [001], and axis, respectively. The color-scale bar at right side of figure denotes the diffraction intensity in arbitrary units.
Mentions: Figure 3(a) shows the zeroth-order Laue zone reflections of the CBED pattern taken at 290 K. The CBED pattern with the incident beam parallel to [001] axis exhibits the symmetry, that is, a 4-fold rotation symmetry around [001] axis and two mirror symmetries respectively perpendicular to [100] and [110] directions. Conversely, as exemplified in Fig. 3(b), the CBED pattern with the incident beam parallel to [100] axis does not exhibit a mirror symmetry perpendicular to [001] axis, while a mirror symmetry perpendicular to [010] axis is maintained. This is not consistent with the centrosymmetric P4/mmm symmetry, but rather agrees with the noncentrosymmetric P4mm structure, which is compatible with the presence of polar axis (electric polarization) along [001] direction. Given the polar crystallographic symmetry, we refined the single crystalline synchrotron x-ray diffractogram and analyzed the crystal structure with reliability factors R = 2.10% and Rwp = 2.49% (Supplemental Information 1). The detail of structural parameters are listed in Table 1.

Bottom Line: We report that a ferroelectric-like metallic state with reduced anisotropy of polarization is created by the doping of conduction electrons into BaTiO3, on the bases of x-ray/electron diffraction and infrared spectroscopic experiments.The crystal structure is heterogeneous in nanometer-scale, as enabled by the reduced polarization anisotropy.The enhanced infrared intensity of soft phonon along with the resistivity reduction suggests the presence of unusual electron-phonon coupling, which may be responsible for the emergent ferroelectric structure compatible with metallic state.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Hongo, Tokyo 113-8656, Japan.

ABSTRACT
We report that a ferroelectric-like metallic state with reduced anisotropy of polarization is created by the doping of conduction electrons into BaTiO3, on the bases of x-ray/electron diffraction and infrared spectroscopic experiments. The crystal structure is heterogeneous in nanometer-scale, as enabled by the reduced polarization anisotropy. The enhanced infrared intensity of soft phonon along with the resistivity reduction suggests the presence of unusual electron-phonon coupling, which may be responsible for the emergent ferroelectric structure compatible with metallic state.

No MeSH data available.