Thermodynamics of formation and electro-magnetic coupling of self-assembled multiferroic thin film nanostructures

The formation and electro-magnetic coupling of self-assembling nanostructures consisting of ferrimagnetic rods embedded in a ferroelectric matrix have been analyzed using a thermodynamic approach. The resulting nanostructure architectures are determined by minimizing the free energy including the elastic energy associated with the epitaxial stresses, which arise during the growth of nanosize constituent phases. The magnetic response to the external electric field has been studied by minimization of the Landau-type free energy for ferrimagnetic and ferroelectric phases with elastic interactions between them. It has been shown that depending on the mechanism of rotation of magnetic moments in single-domain nano-rods the external electric field induces a continuous or discontinuous change of magnetization. The formation of a CoFe2O4 PbTiO3 nanostructure grown on SrTiO3 substrate and its response to an electric field is considered as an example.