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Anharmonicity and weak modes assignment in LaSrCuO with oxygen isotopic substitution

Eirini Siranidi 1Dimitris Tsamakis 1Efthymios P. Liarokapis 1Kazimierz Conder 2

1. National Technical University of Athens (NTUA), Heroon Polytechneiou 9, Athens 157 80, Greece
2. Paul Scherrer Institut (PSI), WLGA, Villigen PSI 5232, Switzerland


The oxygen isotope effect on the first and second order Raman scattering of high-quality La2-xSrxCu16,18O4 (80% substitution 16O by 18O) polycrystalline compounds with x=0.00, 0.015 has been investigated. Measurements were obtained on microcrystallites in the approximate (zz) and (xx/yy) scattering configuration, at low temperatures (down to 10K). The soft mode that appears in the first order zz spectra related with the orthorhombic-to-tetragonal phase transition shows a deviation from the harmonic law at all temperatures studied. The apex oxygen mode follows quite well the mass harmonic law, even at low temperatures. A broad band of apparent B1g symmetry in the region of 300-330 cm-1 of the (xx) polarization spectra seems to consist of two modes, one of which shifts with the isotopic substitution and the other is not shifted and therefore is due to La atoms vibrations. Concerning the second order Raman scattering several weak and strong peaks have been observed and categorized to those that involve vibrations of the oxygen atoms or the heavy elements.


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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium K, by Eirini Siranidi
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 17:19
Revised:   2009-06-07 00:44