RAMAN-SCATTERING INVESTIGATION OF Y2BANIO5

Raman scattering spectra of Y2BaNiO5 have been measured in the tempera ture region between 7 K and 530 K, and also an infrared absorption spe ctrum has been measured at room temperature. We have observed the A(g) phonon modes at 244 and 532 cm(-1), B-2g at 171 and 322 cm(-1), and B -3g at 178, 257 and 435 cm(-1), respectively. For only (a, a) spectrum among the A(g) spectra, a strong doublet peak at about 760 cm(-1) and a weak triplet peak at about 1500 cm(-1) have been found. With the in crease of temperature, the doublet peak becomes single peak and the tr iplet peak almost disappears in the higher temperature region than 400 K, where magnetic susceptibility shows the maximum. This suggests tha t these peaks can be related to the magnetic excitations.