Conférence du Professeur Antonio Garcia Martin de l'Instituto de Microelectronica de Madrid le mardi 4 mars 2014 à 14h30
Titre de la présentation : << Magnetoplasmonics : the interplay between magneto-optics and plasmonics >>.
MAGNETOPLASMONICS: THE INTERPLAY BETWEEN MAGNETO-OPTICS AND PLASMONICS
Subwavelength composite materials constitute an interesting path towards the development of materials with “on demand” optical properties. We will present our latest results on systems composed of both noble and ferromagnetic metals, which we denote as magnetoplasmonic. While noble metals have intense and narrow plasmon resonances they lack magneto-optical (MO) activity at reasonable magnetic field intensities. On the other hand, ferromagnetic metals are MO active but their plasmon resonances are weak and broad. By combining both kinds of materials we intend to obtain systems that simultaneously exhibit plasmon resonances and MO activity.
In this talk I will review our current understanding on the topic, addressing that it is possible to both (1) enhance the magneto-optical activity of the system via surface plasmon excitation, and (2) modulate the plasmon properties via application of a magnetic field [i,ii].
We will focus on Localized Surface Plasmon Resonances (LSPRs), that greatly influence the optical [iii,iv] and magneto-optical (MO) [v,vi,vii,viii,ix] properties of fully metallic and metal-dielectric nanostructures. We will analyze the MO response of isolated nanodisks, where we will show how the excitation of the LSPR produces an enhancement of the MO activity . The observed enhancement in the MO is attributed to the high intensity of the electromagnetic (EM) field inside the nanostructure when the LSPR occurs. Here we show how the EM profile related to the LSPR can be probed locally inside the nanostructure by measuring the MO activity of the system as a function of the position a MO active probe (a Co nanolayer) [x]. This EM field profile is the key element in the analysis of the MO activity and thus a clever engineering would make it possible to get large MO effect and low losses [xi]. We will then show that interactions play a key role in the magneto-optical response. The structures consist of a pure Au nanodisk separated by a SiO2 spacer from a MO component constituted by a 4nmAu/2nmCo multilayer nanodisk, which exhibits perpendicular magnetic anisotropy, reducing the required magnetic field to achieve saturation in polar configuration. We will analyze the magnetic response of the system and present a very simple model that contains all the physical ingredients of the actual structure