Transverse Kerr Effect Research Articles

Near-Perfect TMOKE in Photonic Crystal Structures for Sensing Devices With High Figure of Merit

Near-perfect transverse magneto-optical Kerr effect (TMOKE), which is realized by sandwiching a magnetic-optical film between a photonic crystal (PhC) structure and a metallic mirror, is studied. Near-unity amplitude in TMOKE is observed owing to the excitation of Tamm plasmon polaritons (TPPs) at the interface between the PhC and the metallic mirror. The physical origin behind such giant enhancement of TMOKE is disclosed by studying the magnetic field distributions at resonance and also confirmed by the reflection spectra of the top PhC and the bottom continuous metallic film. Besides, the suitability and the sensitivity of the proposed structure for sensing both gas and aqueous mediums are also illustrated in the last. And it is found that the excellent performance with the averaged figure of merit (FoM) on the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.8\times10^{3}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.7\times10^{3}$ </tex-math></inline-formula> can be achieved for sensing gas and aqueous mediums, respectively. We hoped that this work will prompt the development of data magnetic storage, optical filters, waveguide isolators, and novel sensors with improved sensitivity.

Sensitivity and reproducibility of transverse magneto-optical Kerr effect (T-MOKE) ellipsometry

We report a comprehensive experimental study to analyze the limiting factors and physical mechanisms that determine the achievable performance of transverse magneto-optical Kerr effect (T-MOKE) ellipsometry. Specifically, we explore different approaches to achieve high sensitivity and reduced acquisition times. The best sensitivity is observed for an incident light polarization with balanced s-p components. We also verify experimentally that the method’s theoretical description is accurately describing data for any s-p combination of the incoming light. Furthermore, two alternative measurement strategies are explored by using different measurement sequences for the polarization sensitive optics, which both achieve a very comparable, high quality of results. Signal-to-noise ratios and systematic deviations are measured and analyzed based on a large number of nominally identical measurement repeats, both for entire signal sequences as well as for individual Fourier components of the magneto-optical signal generated by a sinusoidal magnetic field sequence. Hereby, we observe that while higher order Fourier components have a significantly reduced signal amplitude and correspondingly exhibit reduced signal-to-noise and repeatability performance, signal-to-noise ratios always exceed values of 100 even for the lowest signal Fourier component and the lowest signal sample that we investigated, illustrating the extremely precise nature of T-MOKE ellipsometry.

Bulk Plasmon Polariton Modes in Hyperbolic Metamaterials for Giant Enhancement of the Transverse Magneto-Optical Kerr Effect.

We demonstrate a concept for the giant enhancement of the transverse magneto-optical Kerr effect (TMOKE) using bulk plasmon polariton (BPP) modes in non-magnetic multilayer hyperbolic metamaterials (HMMs). Since the BPP modes are excited through the attenuated total reflection (ATR) mechanism, using a Si-based prism-coupler, we considered a single dielectric magneto-optical (MO) spacer between the prism and the HMM. The working wavelength was estimated, using the effective medium approach for a semi-infinite dielectric-plasmonic multilayer, considering the region where the system exhibits type II HMM dispersion relations. Analytical results, by means of the scattering matrix method (SMM), were used to explain the physical principle behind our concept. Numerical results for giant TMOKE values (close to their maximum theoretical values, ) were obtained using the finite element method (FEM), applying the commercial software COMSOL Multiphysics. Our proposal comprises a simple and experimentally feasible structure that enables the study of MO phenomena in HMMs, which may find application in future nanostructured magnetoplasmonic metamaterials for active nanophotonic devices.

Optimization of Magnetoplasmonic ε-Near-Zero Nanostructures Using a Genetic Algorithm.

Magnetoplasmonic permittivity-near-zero (-near-zero) nanostructures hold promise for novel highly integrated (bio)sensing devices. These platforms merge the high-resolution sensing from the magnetoplasmonic approach with the -near-zero-based light-to-plasmon coupling (instead of conventional gratings or bulky prism couplers), providing a way for sensing devices with higher miniaturization levels. However, the applications are mostly hindered by tedious and time-consuming numerical analyses, due to the lack of an analytical relation for the phase-matching condition. There is, therefore, a need to develop mechanisms that enable the exploitation of magnetoplasmonic -near-zero nanostructures’ capabilities. In this work, we developed a genetic algorithm (GA) for the rapid design (in a few minutes) of magnetoplasmonic nanostructures with optimized TMOKE (transverse magneto-optical Kerr effect) signals and magnetoplasmonic sensing. Importantly, to illustrate the power and simplicity of our approach, we designed a magnetoplasmonic -near-zero sensing platform with a sensitivity higher than and a figure of merit in the order of . These last results, higher than any previous magnetoplasmonic -near-zero sensing approach, were obtained by the GA intelligent program in times ranging from 2 to 5 min (using a simple inexpensive dual-core CPU computer).

Ultrafast element- and depth-resolved magnetization dynamics probed by transverse magneto-optical Kerr effect spectroscopy in the soft x-ray range

We report on time- and angle-resolved transverse magneto-optical Kerr effect spectroscopy in the soft x-ray range that, by analysis via polarization-dependent magnetic scattering simulations, allows us to determine the spatio-temporal and element-specific evolution of femtosecond laser-induced spin dynamics in nanostructured magnetic materials. In a ferrimagnetic GdFe thin film system, we correlate a reshaping spectrum of the magneto-optical Kerr signal to depth-dependent magnetization dynamics and disentangle contributions due to non-equilibrium electron transport and nanoscale heat diffusion on their intrinsic time scales. Our work provides a quantitative insight into light-driven spin dynamics occurring at buried interfaces of complex magnetic heterostructures, which can be tailored and functionalized for future opto-spintronic devices.

Giant enhancement of the transverse magneto-optical Kerr effect based on the Tamm plasmon polaritons and its application in sensing

The giant enhancement of the transverse magneto-optical Kerr effect (TMOKE) is investigated. It is achieved by depositing a multilayer structure in the form of alternating magnetic and nonmagnetic dielectric film on a metallic mirror supported by a dielectric substrate. The results show that near perfect TMOKE is realized owing to the Tamm plasmon polaritons (TPPs) excited between the multilayer structure and the metallic mirror, which is confirmed by illustrating the distributions of the magnetic field at resonance. Besides, the potential applications of the giant enhancement of the TMOKE on the sensing are also illustrated in the last. It is believed that the proposed structures in this work are promising for the development of 3D imaging, data storage and novel sensors with high sensitivity.

Observation of optical gyromagnetic properties in a magneto-plasmonic metamaterial

Metamaterials with artificial optical properties have attracted significant research interest. In particular, artificial magnetic resonances with non-unity permeability tensor at optical frequencies in metamaterials have been reported. However, only non-unity diagonal elements of the permeability tensor have been demonstrated to date. A gyromagnetic permeability tensor with non-zero off-diagonal elements has not been observed at the optical frequencies. Here we report the observation of gyromagnetic properties in the near-infrared wavelength range in a magneto-plasmonic metamaterial. The non-zero off-diagonal permeability tensor element causes the transverse magneto-optical Kerr effect under s-polarized incidence that otherwise vanishes if the permeability tensor is not gyromagnetic. By retrieving the permeability tensor elements from reflection, transmission, and transverse magneto-optical Kerr effect spectra, we show that the effective off-diagonal permeability tensor elements reach 10−3 level at the resonance wavelength (~900 nm) of the split-ring resonators, which is at least two orders of magnitude higher than magneto-optical materials at the same wavelength. The artificial gyromagnetic permeability is attributed to the change in the local electric field direction modulated by the split-ring resonators. Our study demonstrates the possibility of engineering the permeability and permittivity tensors in metamaterials at arbitrary frequencies, thereby promising a variety of applications of next-generation nonreciprocal photonic devices, magneto-plasmonic sensors, and active metamaterials.

Experimental confirmation of the delayed Ni demagnetization in FeNi alloy

Element-selective techniques are central for the understanding of ultrafast spin dynamics in multi-element materials, such as magnetic alloys. Recently, however, it turned out that the commonly used technique of the transverse magneto-optical Kerr effect (T-MOKE) in the extreme ultraviolet range may have issues with unwanted crosstalk between different elemental signals and energy-dependent non-linear response. This problem can be sizeable, which puts recent observations of ultrafast spin transfer from Fe to Ni sites in FeNi alloys into question. In this study, we investigate the Fe-to-Ni spin transfer in a crosstalk-free time-resolved x-ray magnetic circular dichroism (XMCD) experiment with a reliable time reference. With XMCD near the absorption maxima, we find a very similar Fe and Ni dynamics as with T-MOKE from identical samples. Considering the potential non-linearities of the T-MOKE response, such a good agreement in our findings is remarkable. Our data provide the ongoing discussion about ultrafast spin-transfer mechanisms in FeNi systems with a broader experimental basis.

Surface plasmon resonance enhanced transverse magneto-optical Kerr effect and the detection performance of nanopore arrays

The introduction of a magnetic component to the surface plasmon resonance (SPR) structure to form a magneto-optical surface plasmonic resonance (MOSPR) detector is an effective method for enhancing the detection limit for small molecules at low concentrations. This is important for biosensing, early disease diagnosis, drug discovery, and the detection of contamination in solutions and gases. In this study, an MOSPR crystal composed of a Co6Ag94 slab covered by a subwavelength periodic square array of gold (Au) nanopores was designed to theoretically examine the mechanism by which MOSPR crystals detect glucose concentrations through the transverse magneto-optical Kerr effect (T-MOKE). Owing to the excitation of SPR at the interface between the glucose solution and Au film, a Fano-like sharp T-MOKE spectrum with a narrow linewidth and a high amplitude was obtained, thus producing a high sensitivity of 159° RIU−1 and a high figure of merit of the order of 103 RIU−1. This corresponds to a glucose detection limit of 0.0066 g ml−1, which is more accurate than that previously reported. This design provides an alternative method for detecting analytes’ concentrations in aqueous environments.

Surface profile-tailored magneto-optics in magnetoplasmonic crystals

The control of transverse magneto-optical Kerr effect (TMOKE) enhancement is realized by balancing the radiative and absorption losses in one-dimensional all-nickel magnetoplasmonic crystals. The modulation of the surface shape tunes the plasmonic radiative losses and coupling of the incident light with surface plasmons. The maximal magneto-optical response corresponds to the optimal coupling implemented with the equality of radiative and absorption losses. A slight deviation from the optimal corrugation depth results in a significant reduction of the TMOKE value.

Nanostructured Hyperbolic Metamaterials for Magnetoplasmonic Sensors

We demonstrate numerically a concept for highly integrated magnetoplasmonic biosensors made with nanostructured magnetooptical (MO) hyperbolic metamaterials (HMMs). The concept is based on the use of enhanced amplitudes of ultranarrow peaks of the transverse magnetooptical Kerr effect (TMOKE). In contrast to conventional magnetoplasmonic transducers that employ wide surface plasmon resonances, we use bulk plasmon polariton modes in HMMs. In sensing through changes in the refractive index of water, a figure of merit on the order of 8 × 102 was observed, to be compared with 590 for non-MO HMMs. This allows for improved resolution detection of low-molecular-weight analytes at concentrations on the order of picomolar.

Magnetic anisotropy and reversal in epitaxial FeGa/IrMn bilayers with different orientations of exchange bias

Epitaxial FeGa/IrMn bilayers with exchange biases along the FeGa[100] and [110] directions are prepared on MgO(001) single crystal substrates by magnetron sputtering through controlling the orientation of the external field &lt;i&gt;in situ&lt;/i&gt; applied during growth. The effect of the exchange bias orientation on the magnetic switching process and the magnetic switching field are studied. The X-ray &lt;i&gt;φ&lt;/i&gt;-scan indicates that the FeGa layer is epitaxially grown with a 45° in-plane rotation on the MgO(001) substrate along the FeGa(001)[110] direction and the MgO(001)[100] direction. The measurements of the angular dependence of the ferromagnetic resonance field and the corresponding fitting to the Kittel equation show that the samples have a superposition of fourfold symmetric magnetocrystalline anisotropy &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}$ {K}_{1} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, unidirectional magnetic exchange bias anisotropy &lt;inline-formula&gt;&lt;tex-math id="M5"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M5.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M5.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, and uniaxial magnetic anisotropy &lt;inline-formula&gt;&lt;tex-math id="M6"&gt;\begin{document}$ {K}_{\mathrm{u}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M6.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M6.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; with configuration of &lt;inline-formula&gt;&lt;tex-math id="M7"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}}//\left[100\right] $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M7.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M7.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; or &lt;inline-formula&gt;&lt;tex-math id="M8"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}}//\left[110\right] $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M8.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M8.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. The combined longitudinal and transverse magneto-optical Kerr effect measurements show that sample with &lt;inline-formula&gt;&lt;tex-math id="M9"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}}//\left[100\right] $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M9.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M9.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; exhibits square loops, asymmetrically shaped loops, and one-sided two-step loops in different external magnetic field directions. In contrast, the sample with &lt;inline-formula&gt;&lt;tex-math id="M10"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}}//\left[110\right] $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M10.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M10.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; exhibits one-sided two-step and two-sided two-step loops as the magnetic field orientation changes. Because the &lt;inline-formula&gt;&lt;tex-math id="M11"&gt;\begin{document}$ {K}_{1} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M11.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M11.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; is superimposed by &lt;inline-formula&gt;&lt;tex-math id="M12"&gt;\begin{document}$ {K}_{\mathrm{u}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M12.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M12.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and &lt;inline-formula&gt;&lt;tex-math id="M13"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M13.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M13.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, the in-plane fourfold symmetry of the magnetic anisotropy energy is broken. The local minima are no longer strictly along the in-plane &lt;inline-formula&gt;&lt;tex-math id="M14"&gt;\begin{document}$ \left\langle{100}\right\rangle $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M14.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M14.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; directions, but make a deviation angle which depends on the relative orientation and strength of magnetic anisotropy. A model based on the domain wall nucleation and propagation is proposed with considering the different orientations of &lt;inline-formula&gt;&lt;tex-math id="M15"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M15.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M15.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, which can nicely explain the change of the magnetic switching route with the magnetic field orientation and fit the angular dependence of the magnetic switching fields, indicating a significant change of domain wall nucleation energy as the orientation of &lt;inline-formula&gt;&lt;tex-math id="M16"&gt;\begin{document}$ {K}_{\mathrm{e}\mathrm{b}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M16.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20220166_M16.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; changes.

Giant Enhancement of the Transverse Magneto-Optical Kerr Effect Based on the Tamm Plasmon Polaritons and its Application in Sensing

Giant Enhancement of the Transverse Magneto-Optical Kerr Effect Based on the Tamm Plasmon Polaritons and its Application in Sensing

Design of Nanoarchitectures for Magnetoplasmonic Biosensing with Near-Zero-Transmittance Conditions.

Nanostructures exhibiting large transverse magneto-optical Kerr effect (TMOKE) are required for magnetoplasmonic biosensing if the aim is the minituarization and integration into microfluidic devices. In this work, we present a general strategy to design nanoarchitectures with enhanced TMOKE, which consist of an arrangement of gold ribs deposited on an magneto-optical (MO) dielectric slab of Bi:YIG (bismuth-substituted yttrium iron garnet) with a SiO2 substrate surrounded by water. Using the finite element method (FEM), we demonstrate numerically that the near-zero-transmittance condition is the most important requirement for high TMOKE values. This can be reached through geometric optimization of the nanoarchitecture by tuning the period, height, and width of the grating, thus leading to resonances at wavelengths where the MO dielectric slab has high MO activity. We also show that the TMOKE amplitude can be further increased if losses in metal ribs are reduced. For a magnetoplasmonic grating with optimized geometry, we demonstrated the potential detection of biologically relevant analytes with sensitivity in the order of 102 nm/RIU (refractive index unit). Since the nanoarchitecture proposed is experimentally feasible with, e.g., nanolithography techniques, one may expect that the design strategy may inspire the development of efficient magnetoplasmonic sensing platforms.

Enhancement of transverse magneto-optical Kerr effects and high sensing performance in a trilayer structure with nanopore arrays

The transverse magneto-optical Kerr effects (T-MOKEs) and sensing performance in a magneto-optical surface plasmon resonance (MOSPR) structure comprising a nanoporous gold/Co6Ag94 bilayer with a square-subwavelength period on a gold slab are theoretically investigated. Benefiting from the excitation of the surface plasmon resonance by optimizing the related parameters of the proposed MOSPR structure, we obtain a magnified T-MOKE signal with a high sensing performance in a gas environment. In this system, a sharp Fano-like T-MOKE spectrum with a narrow linewidth and a high amplitude is achieved. This strategy is important for obtaining new classes of detectors for monitoring air quality.

Two-dimensional array of iron-garnet nanocylinders supporting localized and lattice modes for the broadband boosted magneto-optics

Abstract We demonstrate a novel all-dielectric magnetophotonic structure that consists of two-dimensional arrays of bismuth substituted iron-garnet nanocylinders supporting both localized (Fabry–Perot-like) and lattice (guided-like) optical modes. Simultaneous excitation of the two kinds of modes provides a significant enhancement of the Faraday effect by 3 times and transverse magneto-optical Kerr effect by an order of magnitude compared to the smooth magnetic film of the same effective thickness. Both magneto-optical effects are boosted in wide spectral and angular ranges making the nanocylinder array magnetic dielectric structures promising for applications with short and tightly focused laser pulses.

Silicon-Based All-Dielectric Metasurface on an Iron Garnet Film for Efficient Magneto-Optical Light Modulation in Near IR Range.

All-dielectric nanostructures provide a unique low-loss platform for efficiently increasing light-matter interaction via excitation of the localized or propagating optical modes. Here, we report on the transverse magneto-optical Kerr effect enhancement in an all-dielectric metasurface based on a two-dimensional array of Si nanodisks on a cerium substituted dysprosium iron garnet thin film. We observed up to 15% light intensity modulation under TM modes excitation. The observed magneto-optical effect is nearly independent of the rotation of the light incidence plane with respect to the metasurface. Being compatible with conventional semiconductor technology, our structure holds promise for device applications, such as light modulators, magnetic and chemical sensors.

Theoretical Study on Metasurfaces for Transverse Magneto-Optical Kerr Effect Enhancement of Ultra-Thin Magnetic Dielectric Films.

We study how to enhance the transverse magneto-optical Kerr effect (TMOKE) of ultra-thin magnetic dielectric films through the excitation of strong magnetic resonances on metasurface with a metal nanowire array stacked above a metal substrate with an ultra-thin magnetic dielectric film spacer. The plasmonic hybridizations between the Au nanowires and substrate result in magnetic resonances. The periodic arrangement of the Au nanowires can excite propagating surface plasmon polaritons (SPPs) on the metal surface. When the SPPs and the magnetic resonances hybridize, they can strongly couple to form two strong magnetic resonances, which are explained by a coupled oscillator model. Importantly, benefitting from the strong magnetic resonances, we can achieve a large TMOKE signal up to 26% in the ultra-thin magnetic dielectric film with a thickness of only 30 nm, which may find potential applications in nanophotonics, magnonics, and spintronics.

Extraordinary transverse magneto-optical Kerr effect through excitation of bulk plasmon polariton modes in type II magneto-optical hyperbolic metamaterials.

In this work, we theoretically demonstrate the giant increment of the transversal magneto-optical Kerr effect in a type II hyperbolic metamaterial composed of four pairs of dielectric/metal layers, where the dielectric material presents magneto-optical activity. The enhancement is a consequence of high localization of the electromagnetic field inside the metamaterial given by excitation of the lowest order-bulk plasmon polariton mode.

Sub-15-fs X-ray pump and X-ray probe experiment for the study of ultrafast magnetization dynamics in ferromagnetic alloys.

In this paper, we present a new setup for the measurement of element-specific ultrafast magnetization dynamics in ferromagnetic thin films with a sub-15-fs time resolution. Our experiment relies on a split and delay approach which allows us to fully exploit the shortest X-rays pulses delivered by X-ray Free Electrons Lasers (close to the attosecond range), in an X-ray pump - X-ray probe geometry. The setup performance is demonstrated by measuring the ultrafast elemental response of Ni and Fe during demagnetization of ferromagnetic Ni and Ni80Fe20 (Permalloy) samples upon resonant excitation at the corresponding absorption edges. The transient demagnetization process is measured in both reflection and transmission geometry using, respectively, the transverse magneto-optical Kerr effect (T-MOKE) and the Faraday effect as probing mechanisms.