Accommodation of transformation strains in transverse multiferroic nanostructures CoFe2O4-PbTiO3

Variable-temperature x-ray diffraction was used to investigate the internal strains that arise from a ferroelectric phase transition in self-assembled multiferroic nanostructures CoFe2O4-PbTiO3 on (001) SrTiO3. The constraints from CoFe2O4 suppressed the c/a ratio in tetragonal PbTiO3 (without affecting its Curie temperature) while the expansion of the out-of-plane lattice parameter in PbTiO3 upon the transition induced tensile out-of-plane strain in CoFe2O4. The transformation strain was partly relieved by the 90 degrees twin domains in PbTiO3 which reduced the net deformation of the component phases. Significant fractions of both c- and a-domains were observed despite the nanoscale of PbTiO3 in the composite films. (c) 2007 American Institute of Physics.