Effects of doping on phonon Raman scattering in the Bi-based 2212 system

Abstract

have been characterized by x-ray-diffraction and Ramanscattering measurements. It is found that the c-axis parameter decreases with increasing doping concentration ͑Pr or La͒ or oxygen content. The softening of the O(2) Sr A g mode corresponds to the decrease of the c-axis parameter. The effect of Pr substitution for Ca on this mode is smaller than that of La substitution for Sr. The shift of the O(1) Cu B 1g mode is related to the ionic size of the doping element. The O(3) Bi A g mode does not exhibit remarkable frequency shift since the Bi-O(3)-Bi force constant nearly remains unchanged upon doping. The effect of oxygen content on the O(2) Sr A g mode in the Bi2212 system is in contrast to that on the corresponding O(4) Ba A g mode in the Y123 system. Change in valence is the dominating effect causing the frequency shift of the O(2) Sr A g mode.

Effect of La Doping on the Crystal Structure, Electric, Magnetic and Morphologic Properties of the BSCCO System

“…Table 5 shows the Raman spectra modes observed. These Raman frequencies are very similar to the frequency shown in the studies of Osada et al 39 and Chen et al 41 .…”

“…The A 1g modes are symmetric for vibrations of Bi, Sr, Ca, Cu, O Bi , O Sr and O Cu in the c axis, as reported by Carvalho and Guedes 40 . It is noted that the samples analyzed in this work exhibit similar behaviors to that one studied by Chen et al 41 , i.e., there are shifts of the Raman mode to lower values and the broadening of the peaks are due to the increasing of dopant contents. The study of Chen et al 41 suggests that such results are consequences of the substitution of aliovalent ions in the sites of the Bi-2212 phase.…”

“…The study of Chen et al 41 suggests that such results are consequences of the substitution of aliovalent ions in the sites of the Bi-2212 phase. Then, changes in the charge of around O(2) Sr , alter the Sr-O(2) bond 39,41 and consequently the excess of oxygen caused by this substitution. This result is in agreement with the XRDs and electric measurements.…”

“…Raman spectroscopy is currently used in the investigation of the phonons and other low-energy excitations in high T C superconductors 38 . There are many works reporting on the assignment of Raman vibrational modes, but these studies are still controversial 39,40,41 . Table 5 shows the Raman spectra modes observed.…”

Structure optimization effects on the electronic and vibrational properties ofBi2Sr2CaCuBellini1, Manghi2, Thonhauser3 et al. 2004Phys. Rev. B15470View full textAdd to dashboardCite

“…In order to keep the discussion manageable, only the data obtained after 1996 will be considered. The strongest debate concerns the origin of the two highest frequencies, i.e., at around 460 and 630 cm Ϫ1 , which were attributed to the motion of the O Bi and O Sr atoms, [32][33][34][35][36] or vice versa. 37 Our calculations, both for the tetragonal and orthorhombic cells, give a strong support to the former type of attribution.…”