Plasmon-assisted high reflectivity and strong magneto-optical Kerr effect in permalloy gratings

Abstract

We demonstrate experimentally a strong plasmon-assisted enhancement of the transverse magneto-optical Kerr effect in permalloy gratings. The enhanced transverse magneto-optical Kerr effect is accompanied by an increased grating reflectivity with the maximum of enhancement being correlated with plasmonic Fano resonances. This correlation was confirmed by an intuitive Fano model and also through full-vectorial optical simulations. Simultaneously high reflectivity and transverse magneto-optical Kerr effect as well as narrowest ferromagnetic resonance linewidth and vanishing anisotropy make permalloy nanostructures attractive for applications in spintronics and nano-optics such as, for example, all-optical excitation of propagating spin waves and spectral tuning of optical nanoantennas.

Transverse magneto-optical Kerr effect in subwavelength dielectric gratings

“…In magneto-plasmonic nanostructures the enhanced TMOKE response is compromised by a relatively low reflectivity of ∼ 20 − 25% (see, e.g., [8,11]). Furthermore, in our work [9] we have shown that the maximum of the TMOKE response occurs at the frequency of the Fano resonance. Due to the asymmetry of the line shape of Fano resonances the maximum of the TMOKE response is often shifted from the maximum of the reflectivity towards its minimum.In this paper, we demonstrate theoretically a large TMOKE response in subwavelength gratings consisting of alternating magneto-insulating and nonmagnetic dielectric nanostripes.…”

“…Finally, we refer to Fig. 3(a) in our work [9] where we investigate a Py grating of the same period as the subwavelength dielectric grating. However, instead of Si the Py grating has air grooves.…”

“…The attainment of a large TMOKE response is important for many practical applications that include, but not limited to, 3D imaging [2], magnonics [3, 4], and MO data storage [1].The natural TMOKE response of continuous single magnetic thin-films is weak and its detection is challenging. Consequently, a large and growing body of research investigates different mechanisms of the enhancement of the TMOKE in thin-film multilayers [5], magneto-plasmonic crystals [6][7][8][9][10][11], and nanoantennas [12,13]. All nanostructures mentioned above consist solely of ferromagnetic and nonmagnetic (e.g., gold) metals or contain a nonmagnetic metal nanostructure combined with a magneto-insulating layer.Pure ferromagnetic magneto-plasmonic nanostructures made, e.g., of nickel (Ni) or permalloy (Py=Ni 80 Fe 20 ) [8,9,12,13] are gaining increasing attention due to their potential for integration with microwave magnonics devices (magnons are the quanta of magnetisation precession in ferromagnetic media).…”

Plasmon-mediated magneto-optical transparency

“…Much smaller values of a control magnetic field are feasible if the plasmonic crystal includes magnetic materials, which is referred to as magneto-plasmonic crystal (MPC). Such an MPC provides outstanding magneto-optical properties as evidenced by significant enhancements of the Faraday and transverse Kerr effects192021222324252627282930. The mostly pronounced enhancement of the magneto-optical effects was found for MPCs containing a perforated noble metal stacked on a magnetic dielectric film27282930.…”

Magneto-plasmonic nanoantennas: Basics and applications

“…Note that only the structures in Panels (a) and (b) were designed to operate as optical devices. Although the structures in the remaining Panels were not designed as such, their metallic nanostructures allow employing them as optical devices, which opens up opportunities for the integration of nanophotonics and nano-magnetism [26,60].…”