Nearly Epitaxial ZrO₂-Co Vertically Aligned Nanocomposites Thin Film with Tunable Magnetic and Optical Anisotropy

Metamaterials have gained great research interest recently owing to their potential for property tunability, multifunctionality, and property coupling. As a new group of hybrid metamaterials, vertically aligned nanocomposite (VAN)-based thin films exhibit significant anisotropic physical properties and a broad range of property tailorability, such as optical anisotropy, magnetic anisotropy, and hyperbolic dispersion. In this work, self-assembled ZrO₂-Co hybrid thin films, with high epitaxial quality and ultra-fine vertically aligned metallic Co nanopillars (with an average diameter of ~ 2 nm) embedded in a ZrO₂ matrix, were successfully fabricated using a pulsed laser deposition (PLD) method. The Co pillar planar density can be effectively tuned, without changing the pillar size, by varying the Co concentration in the target, which results in tunable optical properties and magnetic properties. Specifically, a high saturation magnetization of 100 emu*cm^-3, strong out-of-plane magnetic anisotropy and tailorable magnetization properties were achieved. Coupled with hyperbolic optical dispersion from 950 nm to 1500 nm in wavelength, plasmonic Co metal nanopillars, and the unique dielectric ZrO₂ matrix, this new nanoscale hybrid metamaterial shows great potential for future integrated optical and magnetic device designs.