Fabrication of high-qualified (Bi₁₋ <i> _x </i>Ba<i> _x </i>)FeO₃ multiferroic thin films by using a pulsed DC reactive sputtering method and demonstration of magnetization reversal by electric field

Abstract

(Bi1−xBax)FeO3 multiferroic thin films with ferromagnetism and ferroelectricity were fabricated by a pulsed DC reactive sputtering and applied to create a magnetic domain using an electric field. The (001)-oriented (Bi1−xBax)FeO3 thin films, the electric polarization direction of which is perpendicular to the film plane, were fabricated onto a non-single-crystalline substrate with a Ta seedlayer/(111)-oriented Pt underlayer. A low pulse frequency (long time for sputtering OFF) and a high sputtering power (high-energy deposition) were effective for the acceleration of the crystallization of the (Bi1−xBax)FeO3 phase owing to the enhancement of the surface diffusion of sputtered atoms on the substrate surface. The saturation magnetization of the film was approximately 90 emu/cm3 and the coercivity was approximately 2.5 kOe. Magnetic force microscopy analysis of the (Bi0.48Ba0.52)FeO3 film confirmed that the magnetization was generated by applying only a local electric field. The multiferroic film described here is expected to be useful for electric-field-driven magnetic devices.