Template-assisted growth of Co-BaTiO3 vertically aligned nanocomposite thin films with strong magneto-optical coupling effect

Oxide-metal based nanocomposite thin films have attracted great interests owing to their unique anisotropic structure and physical properties. A wide range of Au-based oxide-metal nanocomposites have been demonstrated, while other metal systems are scarce due to the challenges in the initial nucleation and growth as well as possible interdiffusions of the metallic nanopillars. In this work, a unique anodic aluminum oxide (AAO) template was used to grow a thin Co seed layer and the following self-assembled metal-oxide (Co-BaTiO 3 ) vertically aligned nanocomposite thin film layer. The AAO template allows the uniform growth of Co-seeds and successfully deposition of highly ordered Co pillars (with diameter < 5 nm and interval between pillars < 10 nm) inside the oxide matrix. Significant magnetic anisotropy and strong magneto-optical coupling properties have been observed. A thin Au-BaTiO 3 template was also later introduced for further enhanced nucleation and ordered growth of the Co-nanopillars. Taking the advantage of such a unique nanostructure, a large out-of-plane (OP) coercive field ( H c ) of ~ 5000 Oe has been achieved, making the nanocomposite an ideal candidate for high density perpendicular magnetic tunneling junction (p-MTJ). A strong polar magneto-optical Kerr effect (MOKE) has also been observed which inspires a novel optical-based reading method of the MTJ states.