Lead based relaxor ferroelectric thin films can become very useful due to their excellent electrical properties, provided the growth difficulties and high cost of fabrication which have stymied their applications are overcome. Our work describes a systematic study of establishing a set of process conditions for reproducible depositions of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) thin films on La0.67Ca0.33MnO3 (LCMO) seeded Pt/TiO2/Glass substrates. Films were grown at ambient temperature using RF- magnetron sputtering. Single phase PMN-PT films could be obtained by ex situ thermal annealing in air for 2 h at temperatures of 550 and 650 °C. Films annealed at temperatures lower than 550 °C and films deposited without the LCMO buffer layer showed presence of pyrochlore phase. Effect of annealing temperature, on the microstructure, dielectric and ferroelectric properties of the PMN-PT films has been investigated. Scanning electron micrographs of single phase PMN-PT films show a bimodal grain size distribution for the thin films annealed at 550 and 650 °C. The films annealed at 650 °C yielded a dielectric constant of 1300 and a remnant polarization (2Pr) of 17 μC cm-2. © 2018 IOP Publishing Ltd.