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Raman study of phonons and crystal-field excitations in NdBa2Cu3-xGaxO7−δ by T Strach; T Ruf; A.M Niraimathi; A.A Martin; M Cardona is a Physics and Astronomy article available to read on EtoBox.

What is Raman study of phonons and crystal-field excitations in NdBa2Cu3-xGaxO7−δ about?

We have performed Raman measurements on a series of NdBa Cu Ga O ceramics 0 -x -0.08 in order to 2 3 yx x 7yd Ž . monitor the influence of Ga doping on the properties of these materials. While the O 4 apex-oxygen phonon exhibits a Ž . ## y1 Ž . Ž . considerable softening of 14 " 2 cm with increasing Ga content between x s 0.00 and 0.08, the O 2 q O 3 in-phase Ž . Ž . phonon frequency is much less influenced. At low temperature, the O 2 -O 3 out-of-phase vibration is split into two peaks 3q Ž . by interaction with a Nd crystal-field CF excitation of similar energy. Using a two-level model, we derive from the spectra the energies of the uncoupled phonon and the CF excitation, as well as the coupling constant of the CF-excitationphonon interaction. The coupling constant and the phonon frequency are almost independent of Ga doping, while the energy Ž . ## y1 of the CF excitation is 5.6 " 1.6 cm lower in NdBa Cu Ga O than in NdBa Cu O . This decrease is 2 2 .9 2 0 .0 8 7yd 2 3 7yd attributed to changes in the positions and charges of the oxygen ions in the CuO planes. Using structural data obtained by 2 neutron diffraction, we perform a point-charge-model calculation to separate structu

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Author

T Strach; T Ruf; A.M Niraimathi; A.A Martin; M Cardona

Publisher

Elsevier Science; Elsevier ; Elsevier BV (ISSN 0921-4534)

Published

1998

Language

EN

Field

Physics and Astronomy (Physical Sciences)