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 CoFe₂ 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-CoFe₂ 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-CoFe₂ layer, highly ordered and uniform single-type core-shell nanopillars (i.e., the CoFe₂ shell with a Au core) form in the TiN matrix. Both cogrowth and templated growth TiN-CoFe₂-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.