We present a polarized Raman scattering study of GdSr2RuCu2O8 single crystals. In this compound, the RuO6 octahedra are rotated around the c axis that in turn gives some Raman activity of the oxygen (ORu) vibrations at 265 cm-1 (A1g), 411 cm-1 (B2g) and 607 cm-1 (B1g). These vibrations, as well as those of the apical oxygen of RuO6 at 654 cm-1 (A1g) and the Cu-plane oxygen at 318 cm-1 (B2g), clearly respond to the onset of magnetic ordering at Tm≈140 K. In particular, the 265 cm-1 mode hardens anomalously with decreasing temperature below Tm. Notably, the corresponding phonon line is absent in the Raman spectra of GdSr2NbCu2O8 (Nb5+:4d0), a compound isomorphic to GdSr2RuCu2O8 (Ru5+:4d3). We argue that the eigenvector of the 265 cm-1 phonon (rotational mode) facilitates efficient modulation of the Ru(t1g)-ORu(p) bands. This modulation gives both Raman scattering strength to the 265 cm-1 mode and strong spin-phonon coupling.
|Number of pages||6|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2001 Oct 1|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics