講演情報
[18a-WL2_201-8]Electronic, optical and magneto-optical properties of CoAu superlattices: first-principles study
〇Keishi Takayama1, Muhammad Arifin1, Kohji Nakamura1 (1.Spintronics Lab., Mie Univ.)
キーワード：
Magneto optical、Superlattice、Optical conductivity
Magnetoplasmonics combines ferromagnetic materials with noble metals to enable simultaneous control of surface plasmon resonances and magneto-optical (MO) effects. Atomic-layer superlattices provide a promising platform for tailoring properties beyond those of bulk materials. In this study, we investigate the electronic structure, optical properties, and MO response of Co/Au atomic-layer superlattices using first-principles calculations. The calculations were performed using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation [1], and the optical conductivity tensor was evaluated using the Kubo formalism [2].
Partial density of states analysis reveals that increasing layer thickness enhances Co–Co interlayer interactions, leading to stronger Co d–d hybridization and a broader electronic bandwidth. The real part of the diagonal optical conductivity exhibits a pronounced peak below 3.5 eV, which redshifts with increasing thickness due to interband transitions near the Fermi level. The imaginary part of the off-diagonal optical conductivity originates from transitions between spin-polarized states near the Fermi level, enabled by spin-orbit coupling. The dielectric function shows a blueshift of the zero-crossing energy around 4.5 eV, while the imaginary part in the visible region exceeds that of bulk Au, indicating enhanced optical loss. The MO quality factor (Q), predominantly governed by the imaginary part of the off-diagonal optical conductivity, reaches maximum values of 0.0606, 0.0249, and 0.0232 for Co1Au1, Co2Au2, and Co3Au3, respectively, within the photon energy range of 0-6 eV, exceeding those reported for Cu/Co (0.0188) and Co/Pd (0.0031) multilayers [3]. These results demonstrate that Co/Au superlattices exhibit enhanced MO performance and are promising candidates for magnetoplasmonic applications.
Partial density of states analysis reveals that increasing layer thickness enhances Co–Co interlayer interactions, leading to stronger Co d–d hybridization and a broader electronic bandwidth. The real part of the diagonal optical conductivity exhibits a pronounced peak below 3.5 eV, which redshifts with increasing thickness due to interband transitions near the Fermi level. The imaginary part of the off-diagonal optical conductivity originates from transitions between spin-polarized states near the Fermi level, enabled by spin-orbit coupling. The dielectric function shows a blueshift of the zero-crossing energy around 4.5 eV, while the imaginary part in the visible region exceeds that of bulk Au, indicating enhanced optical loss. The MO quality factor (Q), predominantly governed by the imaginary part of the off-diagonal optical conductivity, reaches maximum values of 0.0606, 0.0249, and 0.0232 for Co1Au1, Co2Au2, and Co3Au3, respectively, within the photon energy range of 0-6 eV, exceeding those reported for Cu/Co (0.0188) and Co/Pd (0.0031) multilayers [3]. These results demonstrate that Co/Au superlattices exhibit enhanced MO performance and are promising candidates for magnetoplasmonic applications.