The Effect of Surface Plasmon Resonances on Spherical Magneto-Plasmonic Fe3O4@Ag Core-Shell Nanoparticles

Abstract In this work, the scattering, absorption, and extinction cross-sections of 𝐹𝑒3𝑂4@Ag core/shell spherical nanostructures embedded in a dielectric host matrix are investigated theoretically. Electrostatic approximation and Maxwell-Garnet effective medium theory are employed to obtain the effective electric permittivity and magnetic permeability, as well as the corresponding absorption, scattering, and extinction cross-sections. Likewise, for a fixed size of QDs (of radius 𝑎𝑠 = 10 nm) numerical analysis is performed to see the effect of varying the metal fraction (𝛽) and the permittivity (𝜀ℎ) of the host matrix on the magneto-plasmonic nanostructures. The results show that graphs of absorption, scattering, and extinction cross-sections as a function of wavelength have two sets of resonance peaks in the UV and visible regions. These sets of peaks arise due to the strong coupling of the surface plasmon oscillations of silver with the excitonic state of the semiconductor/dielectric at the inner (𝐹𝑒3𝑂4@Ag) and outer (Ag/host) interfaces. The absorption and scattering crosssections are blue-shifted in the first peak and red-shifted for the second set of peaks as 𝛽 increases. Similarly, the extinction cross-section possesses two sets of resonance peaks which are enhanced for an increase in 𝜀ℎ or decrease of 𝛽; keeping one of these two parameters constant at a time. The results obtained may be utilized in applications that incorporates both the plasmonic and magnetic effects in core/shell nanostructures.