Depression in strength of the infrared active Eu mode with Ce-doping in Nd2-χCeχCuO4

✍ Scribed by T. Hirata; S. Uji; H. Aoki

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 331 KB
• Volume: 168
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(90)90080-x

✦ Synopsis

Infrared spectra measurements revealed that the highest energy F_~ mode ( ~ 530 cm -m ) assigned to the in-plane Cu-O stretching motion in the T' structure, becomes weak in its strength with Ce-doping up to x=0.2 in Nd2_xCexCuO4 while its energy shifts dOwnwards. It is concluded that the depression of the phonon's strength is associated with a conversion to the Cu I + conftgnration (Cu 2+ diminution) as the doping level increases, and that the presence of Cu t + with an ionic radius larger than Cu 2+ also accounts for the downward shift of the F_~ mode affecting the Cu-O bond length as the lattice parameter "a" increases with increasing of the dopant. In fact, the strength as well as the energy of the F_~ correlated well with the valence state of Cu on the basis of charge neutrality for Nd2_xCexCuO4 with different doping levels.