Raman Scattering Investigation of Y₂BaNiO₅

Raman scattering spectra of Y₂BaNiO₅ have been measured in the temperature region between 7 K and 530 K, and also an infrared absorption spectrum 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 increase of temperature, the doublet peak becomes single peak and the triplet peak almost disappears in the higher temperature region than 400 K, where magnetic susceptibility shows the maximum. This suggests that these peaks can be related to the magnetic excitations.