Enhancement Of Magneto-optical Kerr Effect Research Articles

Transverse magneto-optical Kerr effect enhancement in si–ni nanogratings by mie and surface lattice resonances

We demonstrate experimentally that a one-dimensional array of silicon nanowires periodically placed on a nickel substrate enhances the transverse magneto-optical Kerr effect (TMOKE) compared to a nickel film. The enhancement mechanism is associated with the excitation of two types of resonances: multipole Mie resonances in each nanowire and surface lattice resonances (SLRs) emerging from the periodic arrangement of the nanowires. The maximal TMOKE values reached up to 1.9 % and 2.6 % due to the excitation of SLR and a magnetic dipole resonance, respectively. When the SLR is excited, the spectral width of the TMOKE enhancement is narrower compared to the case of the magnetic dipole resonance.

Transverse Magneto-Optical Kerr Effect Enhancement in Si–Ni Nanogratings by Mie and Surface Lattice Resonances

Transverse Magneto-Optical Kerr Effect Enhancement in Si–Ni Nanogratings by Mie and Surface Lattice Resonances

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.

Enhancing the magneto-optical Kerr effect through the use of a plasmonic antenna.

We employ an extended finite-element model as a design tool capable of incorporating the interaction between plasmonic antennas and magneto-optical effects, specifically the magneto-optical Kerr effect (MOKE). We first test our model in the absence of an antenna and show that for a semi-infinite thin-film, good agreement is obtained between our finite-element model and analytical calculations. The addition of a plasmonic antenna is shown to yield a wavelength dependent enhancement of the MOKE. The antenna geometry and its separation from the magnetic material are found to impact the strength of the observed MOKE signal, as well as the antenna's resonance wavelength. Through optimization of these parameters we achieved a MOKE enhancement of more than 100 when compared to a magnetic film alone. These initial results show that our modeling methodology offers a tool to guide the future fabrication of hybrid plasmonic magneto-optical devices and plasmonic antennas for magneto-optical sensing.

Interference induced enhancement of magneto-optical Kerr effect in ultrathin magnetic films

We have studied the magneto-optical spectra of ultrathin magnetic films deposited on Si substrates coated with an oxide layer (SiOx). We find that the Kerr rotation angle and the ellipticity of ~1 nm thick CoFeB thin films, almost transparent to visible light, show a strong dependence on the thickness of the SiOx layer. The Kerr signal from the 1 nm CoFeB thin film can be larger than that of ~100 nm thick CoFeB films for a given SiOx thickness and light wavelength. The enhancement of the Kerr signal occurs when optical interference takes place within the SiOx layer. Interestingly, under such resonance condition, the measured Kerr signal is in some cases larger than the estimation despite the good agreement of the measured and calculated reflection amplitude. We infer the discrepancy originates from interface states that are distinct from the bulk characteristics. These results show that optical interference effect can be utilized to study the magneto-optical properties of ultrathin films.

Enhancement of magneto-optical Kerr effect by surface plasmons in trilayer structure consisting of double-layer dielectrics and ferromagnetic metal.

Giant enhancement of the magneto-optical Kerr effect (MOKE) by surface plasmon polaritons (SPPs) is theoretically shown in a trilayer structure consisting of double-layer dielectrics and a ferromagnetic metal (Al2O3/SiO2/Fe). We calculated the resonant enhancement of the transverse MOKE (TMOKE) and polar MOKE (PMOKE) using the attenuated total reflection (ATR) configuration with the transfer matrix method using a 4 × 4 scattering matrix. At a specific film thickness of the low-index SiO2 layer, where confinement of the SPPs on the Fe surface becomes close to the cutoff condition, the incident light from the Al2O3 couples with the SPPs at the SiO2/Fe boundary most efficiently, resulting in resonant enhancement of the MOKE at an incident angle corresponding to the wave vector of the SPPs. The calculated PMOKE showed orthogonal transformation (90°-rotation) and almost full-orbed deformation (44°-ellipticity) of the polarization, and the TMOKE showed a change in reflectance of about 34 dB upon magnetization reversal.

Angle dependence of the photonic enhancement of the magneto-optical Kerr effect in DMS layers

We investigate theoretically an angle dependence of the enhancement of the polar magneto-optical Kerr effect (MOKE) obtained thanks to a deposition of a paramagnetic Diluted Magnetic Semiconductor (DMS) layer on a one-dimensional photonic crystal layer. Our transfer-matrix-method–based calculations conducted for TE and TM polarizations of the incident light predict up to an order of magnitude stronger MOKE for a (Ga,Fe)N DMS layer when implementing the proposed design. The maximum enhancement for TE and TM polarization occurs for the light incidence at the normal and at the Brewster angle, respectively. This indicates a possibility of tuning of the MOKE enhancement by adjustment of the polarization and of the incidence angle of the light.

Giant magneto-optical Kerr effect in HfO2/Co/HfO2/Al/silicon structure

An extraordinary enhancement of magneto-optical Kerr effect was demonstrated in HfO2/Co/HfO2/Al/substrate composite structure by experimental measurements as well as theoretical calculations. Giant polar Kerr rotation was observed within a broad spectral region, and especially a peak of −7.92° was found at wavelength of 496 nm, which is nearly forty times as large as that of a single Co film. In addition, a Kerr rotation reversal was also observed in short wavelength region in the longitudinal geometry. We proposed that the multiple reflections and optical interference in the optical cavities lead to the enormous enhancement and modulation of the Kerr rotation.

Contribution of Au nanoparticles to the longitudinal magneto-optical Kerr effect of Bragg reflector based magneto-plasmonicmultilayers

In this paper, we investigate a significant enhancement of the longitudinal magneto-optical Kerr effect when a magneto-optical thin film is covered by the Bragg reflector mirror and Au nanoparticles on its right and left side respectively. Our results indicate the sufficient longitudinal magneto-optical Kerr effect enhancement in this new structure by the aid of combination of surface plasmon resonance and light localization in magneto-optical garnet layer at one practical communication wavelength in the middle of the visible spectrum. These results confirmed by the aid of Finite difference frequency domain simulation method.

Hydrogen absorption induced reversible effect on magneto-optical property of Pd/Fe, Pd/Co and Pd/Ni bilayers

We report on the reversible change of the magneto-optical Kerr effect (MOKE) in Pd covered magnetic thin films by controlling H2 absorption. After H2 exposure, the extinction angle of MOKE was shifted and correspondingly the Kerr intensity was significantly increased. When properly choosing the analyzer angle, we obtained large enhancement of 40%, 35% and 50–70% for Pd/Fe, Pd/Co and Pd/Ni bilayers, respectively. The time-dependence of this H2 absorption effect on MOKE was investigated. The reversibility of MOKE enhancement was demonstrated in Pd/Ni bilayer by multiple cycles (at least 4 times) of H2 absorption and desorption. These observations reveal the universal responses when combining the hydrogenated Pd layer with a magnetic thin film, and can be applied in various magnetic materials.

Longitudinal Magneto-Optical Kerr Effect in Magneto-Plasmonic Heterostructures

In this paper, the effect of Au nanoparticles and a Bragg reflector mirror on the optical and longitudinal magneto-optical Kerr effect of a new magneto-plasmonic structure has been investigated. The new magneto-plasmonic heterostructure consists of a Bragg reflector mirror beside a crystalline Ce:YIG thin film incorporating gold nanoparticles. Our results indicate sufficient broad band longitudinal magneto-optical Kerr effect enhancement in this new structure using the combination of surface plasmon resonance and Bragg reflector mirror.

Cavity Enhanced Longitudinal Magneto-Optical Kerr Effect in Magneto-Plasmonic Multilayers Consisting of Ce: YIG Thin Films Incorporating Gold Nanoparticles

Enhanced magneto-optical rotation has been the subject of intense interest for communication technology. In this paper, we report an experimental study on the effect of Bragg reflector mirror and Au nanoparticles on the magneto-optical rotation in a new magneto-optical structure named magneto-plasmonic construction. Our results indicate sufficient longitudinal magneto-optical Kerr effect enhancement in this new structure by the aid of combination of surface plasmon resonance and light localization in magneto-optical garnet layer. The presence of Au nanoparticles leads to screening of the surface plasmon resonance, while Bragg reflector mirror reduces the group velocity in magneto-optical medium as a defect layer and thus we have sufficient enhancement in magneto-optical rotation. These structures can be addressed as a new concept in the development of magneto-plasmonic devices.

Magneto-optical Kerr effect enhancement at the Wood's anomaly in magnetoplasmonic crystals

Magneto-optical Kerr effect enhancement in longitudinal and transversal configurations is systematically studied in one- and two-dimensional magnetoplasmonic crystals based on the nanostructured nickel films. Spectral dependences of magneto-optical effects demonstrate resonant features with the Fano-type lineshape in the spectral vicinity of the Wood's anomaly associated with excitation of surface magnetoplasmons in Voigt and Faraday configurations, respectively.

Diffracted magneto-optical Kerr effect in one-dimensional magnetic gratings

One-dimensional Co2MnSi magnetic gratings were fabricated with a significant ease by using the interference pattern of two femtosecond-laser beams which resulted in a selective-area annealing of the as-deposited Co2MnSi film. The longitudinal Kerr rotation of the negative first-order diffracted beam was nearly 30 times larger than that of the zeroth-order one in a sample fabricated with the optimal conditions. The enhancement strongly depends on the grating depth, which varies with the number of laser shots, confirming the theoretical result that the magneto-optical Kerr-effect enhancement is reduced as the grating depth increases.

Magneto-optical Kerr effect in Co x Ag1-x nanostructured granular films

A series of Co x Ag 1- x nanostructured granular films have been prepared by ion beam sputtering and annealed at 100, 250, 400, 500℃. The optical constants, the complex dielectric function and magneto-optical Kerr parameters were measured at room temperature. For the samples having low Co compositions, the strong Kerr effect enhancement is observed around the Ag plasma edge. With an increase in annealing temperature, the resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. From the analysis of the numerical calculations, it is concluded that the magneto-optical Kerr effect enhancement (MOKE) is due to the presence of the steep plasma edge.

Giant magneto-optical Kerr effect enhancement in layered CoMn/Si structures

For sputtered Co57Mn43/Si film samples with different ferromagnetic thickness, the spectra of the complex magneto-optical polar Kerr rotation and optical constants were ex-situ measured. For 5 nm-thick Co57Mn43 film, the Kerr rotation around 4.3 eV was enhanced by a factor of about 10 times with lower loss of the signal intensity as compared to the thick film. Numerical calculations show that the enhancement effect is attributed to an interplay between optical properties of Co57Mn43 and substrate Si that has a strong interband transition (E2) near 4.3 eV.

The Magneto-Optical Kerr Effect Enhancement in CoxAg1?x Granular Films

The magneto-optical Kerr effect enhancement in Co y Ag 1 , granular magnetic films anncaled at 100, 250, 400, 500 °C was studied. The optical constants the complex dielectric function and magneto-optical Kerr patameters were measured at room temperature. For the sample Co 2 Ag 98 , strong Kerr effect enhancement is observed around the Ag plasma edge. With increasing annealing temperature. the values of the kerr rotation θ k and Kerr ellipticity e K increase, resonance-like peaks appear in the Kerr rotation, and the peak positions are shifted toward the low photon energy region. As the Co composition x inereases the Kerr effect enhancement is weakened and disappears for x ≥ 50%. From the analysts of the experimeatal data, it is concluded that the magnetooptical Kerr effect enhancement is due to the presence of the steep plasma edge.

Optical Properties and Reactive Sputtering Conditions of AIN and AlSiN Thin Films for Magneto- Optical Applications

The dependence of the refractive index and film thickness of AlN and AlSiN thin films on the reactive sputtering conditions (N2 partial pressure, total pressure, and rf sputtering power) have been studied in detail and analyzed in terms of the mechanism of reactive sputtering and the target poisoning phenomenon. On the basis of the results, the sputtering conditions of AlN and AlSiN films have been optimized for magneto-optical applications. The AlN and AlSiN films after optimization of the sputtering conditions had very high transmissivity and refractive index, and were suitable for magneto-optical Kerr effect enhancement. A marked enhancement of the magneto-optical Kerr effect for a TbFeCo film coated with AlN and AlSiN films was observed. The improvement of the signalto-noise ratio obtained with the AlSiN film was greater than the AlN film.

Enhancement of magneto-optical Kerr effect in layered films

It is shown that low optical constants of the reflecting substrate of metallic bilayers for magneto-optical Kerr effect (MOKE) enhancement can be obtained around wavelength 800 nm either in a thin noble metal layer or in a dielectronic/noble metal double layer reflector. Analyses also indicate that low optical constants can be obtained at any visible/near infrared wavelength with a dielectric/metal double layer. A method of designing the magnetic layers for MOKE enhancement is proposed.

A study of the magneto-optical Kerr effect in layered films

Different concepts toward enhancement of magneto-optical Kerr effect in layered films are discussed and compared. A method of designing the layered films is proposed.