Ultrathin Ternary FeCoNi Alloy Nanoarrays in BaTiO<sub>3</sub> Matrix for Room-Temperature Multiferroic and Hyperbolic Metamaterial.

Huang, Jijie; Li, Leigang; Hu, Zedong; Tsai, Benson Kunhung; Huang, Jialong; Shen, Jianan; Zhang, Yizhi; Barnard, James P et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

Multifunctional vertically aligned nanocomposite (VAN) thin films exhibit considerable potential in diverse fields. Here, a BaTiO<sub>3</sub>-FeCoNi alloy (BTO-FCN) system featuring an ultrathin ternary FCN alloy nanopillar array embedded in the BTO matrix has been developed with tailorable nanopillar size and interpillar distance. The magnetic alloy nanopillars combined with a ferroelectric oxide matrix present intriguing multifunctionality and coupling properties. The room-temperature magnetic response proves the soft magnet nature of the BTO-FCN films with magnetic anisotropy has been demonstrated. Furthermore, the anisotropic nature of the dielectric-metal alloy VAN renders it an ideal candidate for hyperbolic metamaterial (HMM), and the epsilon-near-zero (ENZ) wavelength, where the real part of permittivity (<i>ε'</i>) turns to negative, can be tailored from ∼700 nm to ∼1050 nm. Lastly, room-temperature multiferroicity has been demonstrated via interfacial coupling between the magnetic nanopillars and ferroelectric matrix.