Tunable Magnetic and Optical Anisotropy in ZrO₂-Co Vertically Aligned Nanocomposites

Metamaterials have gained great research interest in recent years owing to their potential for property tunability, multifunctionality, and property coupling. As a new group of self-assembled thin films, vertically aligned nanocomposite (VAN)-based hybrid metamaterials have been demonstrated with significant anisotropic physical properties and a broad range of property tailorability, such as optical anisotropy, magnetic anisotropy, hyperbolic dispersion, and enhanced second harmonic generation properties. Herein, self-assembled ZrO₂-Co nanocomposite films, with high epitaxial quality and ultra-fine vertically aligned Co nanopillars (with an average diameter of ≈2 nm) embedded in a ZrO₂ matrix, are fabricated using a pulsed laser deposition (PLD) method. The Co pillar density can be effectively tuned 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 are achieved via tuning the Co nanopillar density. Coupled with hyperbolic dispersion of dielectric constant from 950 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.