Self-assembled multiferroic nanostructures in the CoFe2O4-PbTiO3 system

The effect of substrate orientation on the morphologies of epitaxial self-assembled nanostructures was demonstrated using multiferroic $0.67\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_3\text{-}0.33\mathrm{Co}{\mathrm{Fe}}_2{\mathrm{O}}_4$ thin films. The two-phase composite films were grown by pulsed laser deposition on single crystal $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ substrates having (001) and (110) orientations. The nanostructures of both orientations consisted of vertical rod- or platelet-like columns of $\mathrm{Co}{\mathrm{Fe}}_2{\mathrm{O}}_4$ dispersed in a $\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_3$ matrix. For the (001) orientation the platelet habits were parallel to the {110} planes, whereas for the (110) orientation the platelets were parallel to the {111} planes. The differences were explained using a thermodynamic theory of heterophase structures.