Effect of sputtering conditions on the structure and magnetic properties of self-assembled BiFeO3-CoFe2O4 nanocomposite thin films

This article describes the growth of self-assembled spinel-perovskite nanocomposite thin films using a sputtering technique. We explore the effects of annealing and sputtering conditions such as working pressure, Ar:O2 ratio, and sputtering power on the structure, morphology, and magnetic properties of BiFeO3-CoFe2O4 nanocomposite thin films. Vertically aligned nanocomposites, consisting of CoFe2O4 grown as pillars in a BiFeO3 matrix, were observed under optimum growth conditions. The magnetic hysteresis loops of these nanocomposites showed a strong out-of-plane anisotropy originating from shape anisotropy of the pillars and magnetoelastic anisotropy of the CoFe2O4, but the latter was dominant. The physical properties of these nanocomposites were dramatically changed by modulating the growth conditions, which affected the growth rates and strain states. Finally, we provide a mapping that summarizes the structure and magnetic anisotropy changes that occur with growth rate, for optimizing synthesis conditions for self-assembled oxide nanostructures.