Abstract
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).
*The authors acknowledge partial support by the National Science Foundation (NSF) Established Program to Stimulate Competitive Research (EPSCoR) under grant number NSF OIA-2044049. This work was also partially supported by the NSF under award numbers DMR 2224456 and 1808715, Air Force Office of Scientific Research under award number FA9550-18-1-0360, Swedish Knut and Alice Wallenbergs Foundation supporting grant titled 'Wide-bandgap semi-conductors for next generation quantum components', and American Chemical Society/Petrol Research Fund, and the Office of Naval Research Young Investigator Program (ONR YIP) under award number N00014-19-1-2384, the University of Nebraska Foundation and the J. A. Woollam Foundation for financial support.
