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Raman Spectroscopic Evidence of a Coherent Room Temperature Hybrid Structure of BaTiO_3 Single Crystal

100%

Liarokapis E., Antonakos A., Kojima A., Yoshimura Y.

Acta Physica Polonica A

2009

vol. 116

issue 1

68-71

Recently, a precession X-ray study has discovered that ferroelectric BaTiO_3 single crystals have a coherent hybrid structure that consists of tetragonal and monoclinic lattices that share the (101) face of the tetragonal [11, 12]. Microscopic observations attest that the single crystal has two kinds of stripes (dark and white regions). Raman spectra of all sides of the cubic crystal have been collected at several scattering configurations. Two kinds of domains have been observed by the Raman measurements within the stripes, which are identified as light and dark spots under the optical microscope. The spectra structures and line widths are strongly affected when the laser direction is parallel to the b-axes and the polarization parallel to the a- or c-axes of the 90° domain (ac-side). It appears that there is a symmetry reduction and disorder, which affects the Raman active phonons. The results are in agreement with the coexistence of the two (tetragonal and monoclinic) lattices.

Anharmonicity and Weak Mode Assignment in La_{2-x}Sr_xCuO_4, with Oxygen Isotopic Substitution

88%

Siranidi E., Lampakis D., Palles D., Liarokapis E., Conder K.

Acta Physica Polonica A

2007

vol. 111

issue 1

173-177

The oxygen isotope effect on the first- and second-order Raman active modes of high-quality La_{2-x}Sr_xCu^{16,18}O_4 (80% substitution ^{16}O by ^{18}O) polycrystalline compounds with x=0.00, 0.015 was investigated at low temperatures. In the second-order Raman scattering several weak and strong peaks were observed and assigned to oxygen atom vibrations. With the isotopic substitution the apex oxygen mode follows quite well the mass harmonic law at all temperatures studied, while the soft mode is anharmonic in the temperature range of 77-180 K and for higher temperatures its anharmonicity is strongly increased. The temperature dependence of the energy of the soft mode for x=0.0 shows also a modification at≈180 K and an abnormal behaviour at≈280 K, which may be related with the transition to the antiferromagnetic phase.

Raman Study in Pr_{0.5}Ca_{0.5}MnO_3 Thin Films

76%

Tatsi A., Papadopoulou E., Lampakis D., Liarokapis E., Prellier W., Mercey B.

Acta Physica Polonica A

2004

vol. 105

issue 1-2

99-106

We report novel Raman measurements made on Pr_{0.5}Ca_{0.5}MnO_3 thin films grown on SrTiO_3 and LaAlO_3 (PCMO/STO and PCMO/LAO, respectively). The measurements were performed for a temperature range 78 K

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3 Acta Physica Polonica A

1 2009

1 2007

1 2004

3 Liarokapis E.

2 Lampakis D.

1 Antonakos A.

1 Conder K.

1 Kojima A.

1 Mercey B.

1 Palles D.

1 Papadopoulou E.

1 Prellier W.

1 Siranidi E.

1 Tatsi A.

1 Yoshimura Y.

Search results

Raman Spectroscopic Evidence of a Coherent Room Temperature Hybrid Structure of BaTiO_3 Single Crystal

Anharmonicity and Weak Mode Assignment in La_{2-x}Sr_xCuO_4, with Oxygen Isotopic Substitution

Raman Study in Pr_{0.5}Ca_{0.5}MnO_3 Thin Films