Intrinsic and extrinsic central peaks in the Brillouin light scattering spectrum of the uniaxial ferroelectric relaxor Sr0.61Ba0.39Nb2O6

Broadband Brillouin scattering of Sr0.61Ba0.39Nb2O6 uniaxial ferroelectric relaxors has been investigated. One broader central peak (CP) appeared at all temperatures and was ascribed to light-induced charge carriers, while the other narrower CP began to appear near the Burns temperature suggesting its origin from the formation of polar nanoregions. Temperature evolution of both CPs indicated one characteristic temperature near 450 K at which the volume and/or density of polar clusters with broken inversion symmetry began to increase resulting in a substantial increase of the intensities of both CPs and coupling between them.