Phonons and magnetic and ferroelectric ordering in La-substituted (Bi 1-xLa x) 0.5Pb 0.5Fe 0.5Ti 0.5O 3 for samples with 0.0 x 0.5 are investigated using Raman, magnetization, and polarization measurements as a function of temperature. The system is tetragonal for pure Bi 0.5Pb 0.5Fe 0.5Ti 0.5O 3 with a large c/a ratio. The anisotropy is reduced when Bi is partially replaced by La (0 x 0.5), and it turns cubic for x 0.4. All the properties are found to change significantly with changes in the c/a ratio. Evidence of spin-glass-like magnetic ordering at low temperature is found in the case of x 0.2. A mechanism for the systematic change of magnetic ordering temperature as a function of doping is also discussed. The phonon frequencies and line widths exhibit discontinuous changes across the tetragonal-cubic transition. Large polarization and forbidden Raman scattering in the cubic phase are explained on the basis of symmetry breaking due to the formation of a polar nano region, which leads to relaxor behavior. © 2011 American Institute of Physics.