Thermally Stable 3D-Metamaterial Designs with Advanced Hyperbolic Dispersion Manipulation and Magnetic Anisotropy

Hybrid metamaterials (HMs) have attracted significant research interests owing to their unique optical properties and their ability to manipulate light-matter interaction in a novel and controlled fashion beyond what any single material offers. Especially 3D HMs are of great interest due to their potential to provide advanced and precise control of such light-matter interaction in nanoscale. In this study, a set of 3D HM nanocomposite films are designed by integrating three phases, i.e., vertically aligned CoFe₂ nanosheets within the matrix of TiN/TaN multilayers. By increasing the number of TiN/TaN multilayers from 2 to 19, a high degree of tunability in optical property has been demonstrated, including well-tailored optical permittivity, and tunable hyperbolic dispersion from Type-II to Type-I. Ferromagnetic CoFe₂ nanosheets introduces novel magnetic responses, such as magnetic anisotropy and enhanced coercivity. Furthermore, in situ heating X-ray diffraction (XRD) suggests good thermal stability of the 3D nanocomposite films up to the measured temperature of 600 °C. This three-phase 3D nanocomposite design offers more flexibility in HM designs, multifunctionalities, and phase stability, compared with the typical two-phase HMs toward future metamaterials by design.