Optical spectroscopic study of PrBa2Cu4O8

The non-superconducting double CuO-chain compound PrBa2Cu4O8 has been studi ed by means of light scattering and infra-red reflection techniques in the temperature range 4-300K. Remarkable anomalies are found in the temperature dependence of the Raman-active phonon frequencies and linewidths, as well as free charge carrier concentration las determined from the reflectivity d ata) around 160K. This is about the same temperature at which anomalies in superconducting YBa2Cu4O8 have been observed, attributed to the opening of a spin Eap. The present observation may indicate a lattice instability to b e the driving force for the anomalies in superconducting as well as non-sup erconducting RBa2Cu4O8. (C) 1998 Elsevier Science Ltd. All rights reserved.