Magneto-Optical Enhancement by Plasmon Excitations in Nanoparticle/Metal Structures

Abstract

Coupling magnetic materials to plasmonic structures provides a pathway to dramatically increase the magneto-optical response of the resulting composite architecture. Although such optical enhancement has been demonstrated in a variety of systems, some basic aspects are scarcely known. In particular, reflectance/transmission modulations and electromagnetic field intensification, both triggered by plasmon excitations, can contribute to the magneto-optical enhancement. However, a quantitative evaluation of the impact of both factors on the magneto-optical response is lacking. To address this issue, we have measured magneto-optical Kerr spectra on corrugated gold/dielectric interfaces with magnetic (nickel and iron oxide) nanoparticles. We find that the magneto-optical activity is enhanced by up to an order of magnitude for wavelengths that are correlated to the excitation of propagating or localized surface plasmons. Our work sheds light on the fundamental principles for the observed optical response and demonstrates that the outstanding magneto-optical performance is originated by the increase of the polarization conversion efficiency, whereas the contribution of reflectance modulations is negligible.

Expanding Effective-Medium Theory to Optical Diamagnetic Responses in Magnetoplasmonic Colloids

“…Not surprisingly, an inspection of the simulated spectra in Fig. 3 clearly reveals that the experimental data can be reproduced only when the plasmon polarizability is included in the model, in accordance with the known fact that plasmons affect the magneto-optic activity [2,6,8,12,14,16]. Outstandingly, the excellent accordance between our model and the experimental data comes entirely from the input of bulk permittivity values obtained from the literature [30][31][32] and in the absence of any parameter fitting.…”

“…One of the most investigated aspects in this field has been the enhanced magneto-optic response mediated by the excitation of localized surface-plasmon resonances (LSPRs) [2,6,8,12,14,16]. By and large, the research in such composite metal-dielectric composites has been essentially focused on the magnification of the optical properties of the magnetic-metal nanostructures.…”

“…By and large, the research in such composite metal-dielectric composites has been essentially focused on the magnification of the optical properties of the magnetic-metal nanostructures. Large magneto-optic activity has been predicted and confirmed experimentally for ferromagnetic-metal nanostructures coupled to plasmon resonances [1, 2,5,6,8,14,16]. These effects are so strong that the enhanced polarizability of small metal clusters has been demonstrated to induce sizable magneto-optic signals even in nonmagnetic metals [17].…”

Magnetoplasmonics: Combining Magnetic and Plasmonic Functionalities

“…[ 149 ] This kind of systems is nowadays object of intense investigation, since they may present extraordinary optical transmission properties. [156][157][158][159][160][161][162] The excitation of propagating plasmons due to the extra momentum provided by the underlying periodic structure gives rise to clear signatures in the refl ectivity of the samples, in a similar fashion as in the ATR confi guration. [156][157][158][159][160][161][162] The excitation of propagating plasmons due to the extra momentum provided by the underlying periodic structure gives rise to clear signatures in the refl ectivity of the samples, in a similar fashion as in the ATR confi guration.…”

Polarizability and magnetoplasmonic properties of magnetic general nanoellipsoids

“…While most of the investigations carried out before were focused on the achievement of substantial enhancement of magneto-optical Kerr effect (MOKE) or Faraday rotation [19][20][21][22][23][24][25], [11] shifted the paradigm of research on magnetoplasmonic functional materials by exploiting the phase tunability of the optical polarizability due to the excitation of LPRs in single nanoparticles and the simultaneous presence of magneto-optical activity in the same ferromagnetic nanostructures. Bonanni et al showed that anisotropic polarizability of the nanostructures due to their shape (circular and elliptical nanodisks) is one of the key parameters and, together with their size and MO properties, affects their magneto-optical response.…”