Tunable opto-magnetic metamaterials via coupled TiN–NiO vertically aligned nanocomposite thin films

Abstract

The integration of plasmonic and magnetic properties in self-assembled hybrid metamaterials offers new opportunities for tunable light–matter interactions in nanoscale thin films. We report a systematic study on laser pulse frequency as a parameter for tuning the microstructure-dependent optical anisotropy and magnetic response in vertically aligned nanocomposites (VANs) composed of plasmonic titanium nitride (TiN) and dielectric nickel oxide (NiO). Using pulsed laser deposition (PLD), TiN–NiO VAN thin films were grown on MgO(001) substrates at various laser frequencies (i.e., 2, 5, and 10 Hz) while keeping all other growth parameters consistent. Structural and morphological analysis reveal that NiO pillar density increases with pulse frequency, enabling controlled modulation of the VAN structure. Ellipsometry data shows that all samples exhibit Type-II hyperbolic dispersion with increased optical anisotropy for samples deposited under higher frequencies. Magnetic hysteresis measurements demonstrate ferromagnetic behavior at both 10 K and 300 K, with enhanced coercivity and out-of-plane anisotropy that correlates with pillar morphology. This tunability allows for enhanced control over the optical and magnetic responses of hybrid metamaterials, enabling the insurgence of novel technologies for data storage, communication, and optoelectronic devices.