0000000000594214
AUTHOR
G. De Marzi
showing 3 related works from this author
Phonon properties of the spinel oxideMgTi2O4with theS=1/2pyrochlore lattice
2003
We study the phonon dynamics of ${\mathrm{MgTi}}_{2}{\mathrm{O}}_{4}$ spinel by measuring the Raman and infrared reflectivity spectra in a wide frequency $(100--3000{\mathrm{cm}}^{\ensuremath{-}1})$ and temperature (10 K--300 K) range. The reflectivity spectra are analyzed by a fitting procedure based on a model which includes both Drude and phonon oscillator contributions to the dielectric constant. The phonon assignment is done from comparison between experimental data and shell model lattice dynamical calculations. We find two infrared-active ${F}_{1u}$ symmetry modes superimposed on the free carrier continuum, and four Raman-active modes of ${1A}_{1g},$ ${1E}_{g},$ and ${2F}_{2g}$ symme…
The effect of Cu substitution on the A1g mode of La(0.7)Sr(0.3)MnO3 manganites
2003
We report on the first Raman data of Cu substituted La(1-y)Sr(y)Mn(1-x)Cu(x)O3 (0 < x < 0.10 and 0.17 < y < 0.3, accordingly in order to have the same Mn(4+)/[Mn(4+)+Mn(3+)] ratio), collected in the frequency range 100-900 cm-1 and at room temperature, with parallel and crossed polarizations of the incident and scattered light. Spectra were fitted with a Drude-Lorentz model, and peaks at 190-220 and 430 cm-1, together with two broad structures centered at near 500 and 670 cm-1, have been found. We also have observed that the A1g mode is substantially shifted with increasing Cu substitution. The A1g phonon shift is a linear function of the tolerance factor t and the rhombohedral …
Effect ofA-site andB-site substitution on the infrared reflectivity spectra ofLa1−yAyMn1−xBxO3(A=Ba,Sr;B=Cu,Zn,Sc;0<y<~0.3;0<~x<~0.1)mang…
2003
We have measured the infrared reflectivity spectra of ${\mathrm{La}}_{1\ensuremath{-}y}[\mathrm{Sr}(\mathrm{Ba}){]}_{y}{\mathrm{Mn}}_{1\ensuremath{-}x}[\mathrm{Cu}(\mathrm{Zn},\mathrm{Sc}){]}_{x}{\mathrm{O}}_{3}$ $(0lyl~0.3,0l~xl~0.10)$ manganites, in a wide frequency $(100\char21{}4000{\mathrm{cm}}^{\ensuremath{-}1})$ and temperature (80 K\char21{}300 K) range. The reflectivity spectra were analyzed by a fitting procedure based on a model that includes Drude, midinfrared electronic, and phonon oscillator contributions to the dielectric constant. Six infrared active ${(3A}_{u}$ and ${3E}_{u})$ modes of rhombohedral symmetry are clearly observed. We assigned all observed modes according to e…