Self-Assembled Complex Three-Phase Core–Shell Nanostructure of Au–CoFe₂–TiN with a Magneto-Optical Coupling Effect

Nanostructured plasmonic–magnetic metamaterials have gained great research interest due to their enhanced magneto-optical coupling effects. Here, we report a complex three-phase nanocomposite design combining ferromagnetic CoFe 2 with plasmonic TiN and Au as a multifunctional hybrid metamaterial using either a cogrowth or a templated method. Via the first method of cogrowing three phases, three different morphologies of Au–CoFe 2 core–shell nanopillars were formed in the TiN matrix. Via the second method of sequential deposition of a TiN–Au seed layer and a TiN–CoFe 2 layer, highly ordered and uniform single-type core–shell nanopillars (i.e., the CoFe 2 shell with a Au core) form in the TiN matrix. Both cogrowth and templated growth TiN–CoFe 2 –Au hybrid systems exhibit excellent epitaxial quality, hyperbolic dispersion, magnetic anisotropy, and a magneto-optical coupling effect. This study provides an effective approach for achieving highly uniform multiphase vertically aligned nanocomposite structures with well-integrated optical, magnetic, and coupling properties.