Nanostructured magneto-optical materials that sustain optical resonances provide an efficient way to control light via the magnetic field, which is of prime importance for telecommunication and sensing applications. However, their response is usually narrowband due to their resonance character. Here, we demonstrate and investigate a type of magnetoplasmonic structure, or quasicrystal, that demonstrates a unique magneto-optical response. It consists of a magnetic dielectric film covered by a thin gold layer perforated by slits, forming a Fibonacci-like binary sequence. The transverse magneto-optical Kerr effect (TMOKE) acquires controllable multiple plasmon-related resonances, resulting in a magneto-optical response over a wide frequency range. In particular, for the experimentally studied samples, the TMOKE resonances are observed in the wavelength range from $\lambda =780\mathrm{nm}$ to $\lambda =970\mathrm{nm}$. Multiband TMOKE is valuable for numerous nanophotonic applications, including optical sensing, control of light, all-optical control of magnetization, etc. TMOKE spectroscopy is also an efficient tool for investigating the peculiarities of plasmonic quasicrystals.

We propose a novel method to enhance the transverse magneto-optical Kerr effect (TMOKE) in the magneto-plasmonic (MP) nanostructures by means of the active dielectric layer. We report the theoretical analysis of the MP structure with a ferromagnetic dielectric doped with rear-earth ions (${\mathrm{Nd}}^{3+}$) as the example of a gain layer. The enhancement takes place near the surface plasmon polariton (SPP) resonances of the nanostructures. The stimulated emission of the dopants in the field of the SPP wave partially compensates its losses. It is shown that due to a decrease of SPP damping, a $Q$-factor of the MP resonance increases and the TMOKE is increased in comparison with the passive nanostructure.

Sensitive vector magnetometry with high spatial resolution is important for various practical applications, such as magnetocardiography, magnetoencephalography, explosive materials detection and many others. We propose a magnetometer based on magnetic iron garnet film possessing a very high magnetic anisotropy, placed in a rotating external magnetic field. Each of the measured magnetic field spatial components produces different temporal harmonics in the out-of-plane magnetization dependence. Our analysis based on numerical simulation shows that the dielectric resonant grating placed on the top of an ultrathin film enhanced the magneto-optical (MO) response by ten times. It allows one to reduce the thickness of the film, which makes it possible to achieve several times higher spatial resolution in the perpendicular to the film direction, up to 30 nm. The reported MO magnetometer allows one to measure simultaneously all three spatial components of the magnetic field with high spatial resolution and sensitivity up to 100 pT Hz ^-1/2 .

We report the enhancement of the magneto-optical Faraday effect in a two-dimensional magnetoplasmonic grating with a square lattice. The structure consists of dielectric magnetic Bi-substituted iron garnet film with low thickness (100 nm) coated by a perforated gold layer. Enhancement of the Faraday rotation by about 2 times is shown experimentally and theoretically despite the suppression of the waveguiding modes. This happens primarily through excitation of surface plasmon polaritons propagating at the Au-garnet interface in two orthogonal directions along lattice vectors of the plasmonic grating.

As magnetized media by their nature have broken time reciprocity, the spatial symmetry of a material is also crucial and it imposes some restrictions on observed optical phenomena. Thus, for the normal incidence of light the spatial inversion symmetry makes transmitted and reflected light insensitive to the direction of the in-plane magnetization of the sample. To avoid this limitation, we propose here an approach based on a magnetoplasmonic structure with broken spatial symmetry. Combination of the specially designed spatial asymmetry with magnetism in the presence of optical losses provides a different effect, the transverse magnetophotonic transmittance effect, notable magnetooptical modulation of the optical transmittance at normal incidence enhanced by surface plasmon excitation. As the phenomenon is sensitive to asymmetry, it can serve as a powerful tool to study spin waves and currents in magnonic and optospintronic devices. The approach to marry the concepts of magnetoplasmonics and a lack of spatial symmetry is promising for the design of nanophotonics devices with outstanding properties.