Nanocolumnar Heterostructure Metamaterial Platforms for Advanced Magnetic and Optical Applications

In this study, we employed a custom-built ultra-high vacuum electron-beam glancing angle deposition technique [1] to fabricate spatially-coherent nanocolumnar heterostructure metamaterials from both hard (cobalt) and soft (permalloy) magnetic materials. Furthermore, we have utilized the atomic layer deposition technique to successfully incorporate a conformal ultrathin interface layer of Al₂O₃ between the magnetic columnar subsegments, thereby enhancing the tunability of magnetic and optical properties. Hence, the anisotropic Bruggeman effective medium model based on the spectroscopic ellipsometry data allowed to extract the dielectric properties of the fabricated structures [2]. Our analysis of the materials also involved the use of generalized vector magneto-optic ellipsometry and vibrating sample magnetometer measurements to determine the magnetic properties. In addition to the experimental work, we conducted a series of systematic micromagnetic and finite element modeling simulations to delve into the fundamental driving mechanisms behind the tunable magneto-optic responses exhibited by the proposed metamaterial platforms. We anticipate that these innovative structural designs may underpin the development of next-generation sensing devices, magnetic recording technologies, and on-chip nanophotonic applications.

[1] Kilic, U., et al. Sci Rep 9, 71 (2019).

[2] Schmidt, D., and Schubert, M., J. Appl. Phys. 114.8 (2013).