Optical modulation and magnetic transition in PbTi_1−xPd_xO_3−δ ferroelectric thin films

The PbTi_1−xPd_xO_3−δ (xPTPO) thin films prepared by chemical solution deposition have been investigated by means of structural characterizations, optical and magnetic measurements. X-ray diffraction patterns show that all the films have a pseudotetragonal perovskite structure, but also exhibit a lattice dilatation behavior and increased internal strain as the x increases. A possible mechanism for strain-induced structural evolution is discussed. Raman scattering further corroborates this change in average structure, where the characteristic variation of phonon modes, indirectly reveal the incorporation of Pd²⁺ ions into host lattice. Transmittance spectra analysis indicates that Pd doping has a key effect on the energy band structure. The optical bandgap of xPTPO films decreases significantly with increasing Pd content, expressed by (3.5–9.0x) eV (0≤x≤0.09). Also, magnetic switching driven by doping has been confirmed in the films, which is attributed to the competition between ferromagnetic and paramagnetic/antiferromagnetic components.