  Here, we report the unusual behaviour shown by the (BiFeO3)1-x-(PbTiO3)x
(BF-xPT) films prepared using a multilayer deposition approach by chemical
solution deposition method. Thin film samples of various compositions were
prepared by depositing several bilayers of BF and PT precursors by varying the
BF or PT layer thicknesses. X-ray diffraction showed that final samples of all
compositions show mixing of the two compounds resulting in a single phase
mixture, also confirmed by transmission electron microscopy. In contrast to
bulk equilibrium compositions, our samples show a monoclinic (MA type)
structure suggesting disappearance of morphotropic phase boundary (MPB) about x
= 0.30 as observed in the bulk. This is accompanied by the lack of any
enhancement of remnant polarization at MPB as shown by the ferroelectric
measurements. Magnetic measurements show that the magnetization of the samples
increases with increasing BF content. Significant magnetization of the samples
indicates melting of spin spirals in the BF-xPT arising from random
distribution of iron atoms across the film. Absence of Fe2+ ions in the films
was corroborated by X-ray photoelectron spectroscopy measurements. The results
illustrate that used thin film processing methodology significantly changes the
structural evolution in contrast to predictions from the equilibrium phase
diagram as well as modify the functional characteristics of BP-xPT system
dramatically.

Materials Science