Origin of Ferroelectricity and Multiferroicity in Binary Oxide Thin Films

The observation of ferroelectric, ferromagnetic and ferroelastic phases in thin films binary oxides attract the broad interest scientists engineers. However, theoretical consideration observed behaviour physical nature was performed mainly for HfO2 from first principles, framework Landau-Ginzburg-Devonshire (LGD) phenomenological approach with a special attention to role oxygen vacancies both cases. Allowing generality LGD theory we applied it group this work. calculations have been assumption that vacancies, as elastic dipoles, can be partially transformed into electric dipoles due defect site-induced and/or surface-induced inversion symmetry breaking (via e.g. piezoelectric effect), "migrate" entire depth an ultra-thin film. We calculated dependence film polarization on voltage room temperature different thickness. Since many oxide are ferroelectric same they multiferroics. Performed shown considered new wide class multiferroics spectra properties useful application nanoelectronics nanotechnology. controlled by choice concentration, thickness technological treatment, such annealing.