Neutron scattering studies on strontium barium niobate

The dispersion of low-energetic phonons is measured on Sr/sub 0.45/Ba/sub 0.55/Nb2O6 single crystals by inelastic neutron scattering at room temperature for the [xi, 0, 0], [xi, xi, 0], and [0, 0, xi] directions. The elastic constants at this temperature are evaluated from the initial slopes of the acoustic branches. From careful measurements at low energy transfer a sequence of weak dispersionless excitations, separated by about 0.5 meV, is found. The appearance of these low-lying flat branches is discussed in connection with the results of quasi-elastic scattering on these samples. (author)