The Kerr and Faraday effects in Co-P films prepared by chemical deposition

The results from experimental studies of the magnetooptical Kerr and Faraday effects in Co-P films are described. It is shown that the angle of rotation of the polarization of light in the polar Kerr effect is a nonmonotonic function of film thickness. Maximum changes in the angle of rotation are observed in the wavelength region of incident radiation for thicknesses comparable to the skin layer. A qualitative model in which the observed effects are attributed to the multilayer structure of the samples under study is described.     

Magnetization-induced second harmonic generation in magnetophotonic microcavities based on ferrite garnets

Magnetization-induced second harmonic generation was observed in magnetophotonic microcavities consisting of a ferromagnetic yttrium-iron garnet layer surrounded by nonmagnetic photonic crystals (Bragg reflectors). At resonance between the fundamental radiation and the microcavity mode in the geometry of polar magnetooptical Kerr effect, the polarization rotation for the second harmonic was found to be (18.5±0.5)°/μm for the fundamental radiation with a wavelength of 825 nm.     

An analysis of the mechanism of Kerr effect enhancement in Mn/Dy/Bi

A study is reported of the structural, magnetic, and magneto-optic properties of Mn/Dy/Bi films obtained by multilayer technology. The maximum Kerr rotation angle in such films is shown to be θ _k =2.25°. Possible reasons for such a large Kerr effect enhancement are considered, namely, an increase in the 6p–3d transition probability caused by symmetry distortion, polarization of the Bi6p band, and a change in the density of states near the Fermi level. The latter reason has been analyzed by simulating the electronic structure of Mn/Dy/Bi through superposition of Dy levels on the MnBi band structure. This approach has revealed possible additional transitions which may be induced by the presence of a Dy buffer and could contribute to the Kerr magneto-optic effect. Fiz. Tverd. Tela (St. Petersburg) 41, 91–97 (January 1999)     

Interrelation between optical and magneto-optical properties of MnSbBi(Pt,Co) films

Results of the study of optical and magneto-optical properties of MnSbBi(Pt, Co) films in a spectral region of 360–820 nm are reported. It is shown that the multilayer MnSbBi(Pt, Co) films obtained by magnetron sputtering possess considerable optical rotation in the geometry of the polar Kerr effect, which is as large as 0.5°–0.7° upon 5-h annealing of the films at 350°C. The spectral dependences measured for the magnitude of the polar Kerr effect showed that these films may be used for laser data recording in the short-wavelength spectral region, which substantially increases the recording density. Studies of the film structure by X-ray and electron diffraction analysis showed that the films have a polycrystalline structure, with granules 15–40 nm in size. Possible causes of a large magnitude of Kerr effect are analyzed.     

Enhancement of the Faraday rotation in magnetically active periodic structures with defects

Relations that determine the field of a light wave transmitted through and reflected from a periodic structure lying on a substrate and containing a defect layer are derived for the case of an arbitrary symmetry of both the defect layer and the layers forming the structure. Exact expressions are obtained for the determination of the positions of the defect modes. The feasibility of a considerable enhancement of the Faraday rotation while retaining 100% transmission through the defect-containing magnetically active structure at a high dielectric contrast is revealed. It is shown that the angle of magnetooptical rotation of the polarization plane in a periodic structure is a bounded quantity.     

Formation of clusters and the magnetooptical Kerr effect in gallium arsenide implanted with manganese ions

The surface morphology and magnetic properties of GaAs irradiated by manganese ions are studied at room temperature using atomic-force microscopy and the magnetooptical Kerr effect. It is shown that ferromagnetism takes place in the surface layer of the irradiated semiconductor subjected to annealing at 715–750°C. The magnetic properties of this layer are related to the evolution of submicron clusters in GaAs doped with Mn.     

Optical and magnetooptical properties of CoFeB/SiO<Subscript>2</Subscript> and CoFeZr/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> granular magnetic nanostructures

The optical and magnetooptical properties of the new granular nanocomposites (CoFeB)/(SiO₂) and (CoFeZr)/(Al₂O₃), which are grains of amorphous ferromagnetic alloys embedded in dielectric matrices, have been studied. The dependence of the optical, magnetooptical, and magnetic properties of the nanocomposites on their qualitative and quantitative composition, as well as on the conditions of their preparation, was investigated. Spectra of the dielectric functions ε = ε₁ ? iε₂ were obtained by the ellipsometric method in the range 0.6–5.4 eV. Above 4.2 eV, the absorption coefficient of the (CoFeB)/(SiO₂) composites was found to be close to zero for all magnetic-grain concentrations. The polar Kerr effect measured at a photon energy of 1.96 eV in dc magnetic fields of up to 15 kOe reaches values as high as 0.25°–0.3° for these nanocomposites and depends only weakly on the conditions of preparation. On the other hand, the (CoFeZr)/(Al₂O₃) nanostructures reveal a considerable difference in the concentration dependences of the Kerr effect between samples prepared in a dc magnetic field and in zero field.     

Compact 1-D magnetophotonic crystals with simultaneous large magnetooptical Kerr rotation and high reflectance

We have investigated the case of reflection-type one-dimensional magnetophotonic crystals (MPCs) in order to achieve high reflectance and high magnetooptical Kerr effect, simultaneously, utilizing a low number of magnetic layers. In a MPC structure including only one Bi:YIG magnetic layer, we have achieved a Kerr rotation as huge as θ_k ≈ 90° with a reflectance of R > 97%. In addition, we have introduced a thinner structure having three Bi:YIG layers and with approximately the same Kerr rotation and reflectance. Both the structures are very compact with lengths of less than 9 μm.     

Magnetic and magnetooptical properties of multilayer ferromagnet-semiconductor nanostructures

The magnetic and magnetooptical properties of spin-tunneling multilayer permalloy-silicon carbide nanoheterostructures deposited by rf sputtering have been studied. Magnetometric and magnetooptical methods are used to show that the magnetic-semiconducting nanostructures have a complex magnetic structure and to track the evolution of the magnetic properties of these structures as functions of the magnetizing field and the thickness and sequence order of ferromagnetic and semiconducting layers in them. The induction response and the field and orientation dependences of the transversal Kerr effect are found to have anomalies. The experimental results are interpreted under the assumption that there is exchange interaction between the ferromagnetic and semiconducting layers through a thin magnetically ordered transition layer formed inside the interface.     

GdFeCo/AlN/TbFeCo薄膜的变温磁化性能研究

用磁控溅射法制备了GdFeCo/AlN/TbFeCo静磁耦合多层薄膜。振动样品磁强计和克尔磁滞回线测试装置的测试结果表明 :2 5℃不加外磁场时GdFeCo/AlN/TbFeCo静磁耦合多层薄膜读出层 (GdFeCo)的极向克尔角为零 ,读出层呈平面磁化 ;12 5℃不加外场时读出层的克尔角最大 (0 .5 4°) ,读出层的磁化方向为垂直磁化 ;随着温度增高 ,读出层由平面磁化转变为垂直磁化 ,在 75℃到 12 5℃温度范围内读出层磁化方向很快从平面磁化转变为垂直磁化。对磁化过程的机理研究表明 :饱和磁化强度和有效各向异性常量影响读出层磁化方向的转变过程 ,但主要受读出层饱和磁化强度的影响 ;在较高温度时读出层的磁化强度较小 ,退磁场能较小 ,在静磁耦合作用下 ,使GdFeCo读出层的磁化方向发生转变。制备的GdFeCo/AlN/TbFeCo静磁耦合多层薄膜适合作CAD MSR记录介质     

MnBi磁性多层膜磁光科尔效应的数值模拟

基于各向异性的平面电磁波传输理论和4×4矩阵法，计算了MnBi，Mn_0.53Bi_0.47，Mn_0.52Bi_0.44Sb_0.04磁性多层膜系列的磁光科尔旋转角、椭圆率随波长、入射角、磁性层厚度变化曲线.计算结果表明，模拟的科尔旋转角、椭圆率随波长变化规律与实验结果吻合很好；在一定波长的垂直入射下，模拟的科尔旋转角、椭圆率随磁性层厚度变化曲线出现科尔谱极大；在磁性层厚度一定的情况下，当入射光以某一角度 关键词： 4×4矩阵法 磁性多层膜 磁光科尔谱 介电张量     

一维磁光子晶体的法拉第效应

由于一维磁光子晶体能同时展示出很好的光透射率和法拉第旋转,故可用于实现小尺度的磁光隔离器。采用传输矩阵法研究了由磁光膜(Bi∶YIG)和电介质膜(Ta2O5,SiO2)构成的一维磁光子晶体,分别讨论了在垂直入射和斜入射条件下的法拉第效应,并给出了几种可行性结构,对磁光隔离器件的进一步改进设计具有一定的参考价值。     

One-dimensional magnetophotonic crystals with magnetooptical double layers

One-dimensional magnetophotonic microcavity crystals with nongarnet dielectric mirrors are created and investigated. The defect layers in the magnetophotonic crystals are represented by two bismuth-substituted yttrium iron garnet Bi:YIG layers with various bismuth contents in order to achieve a high magnetooptical response of the crystals. The parameters of the magnetophotonic crystal layers are optimized by numerical solution of the Maxwell equations by the transfer matrix method to achieve high values of Faraday rotation angle Θ _F and magnetooptical Q factor. The calculated and experimental data agree well with each other. The maximum values of Θ _F =–20.6°, Q = 8.1° at a gain t = 16 are obtained for magnetophotonic crystals with m = 7 pairs of layers in Bragg mirrors, and the parameters obtained for crystals with m = 4 and t = 8.5 are Θ _F =–12.5° and Q = 14.3°. It is shown that, together with all-garnet and multimicrocavities magnetophotonic crystals, such structures have high magnetooptical characteristics.     

Thermal stability of amorphous SiOC/crystalline Fe composite

We examined the thermal stability of amorphous silicon oxycarbide (SiOC) and crystalline Fe composite by in situ and ex situ annealing. The Fe/SiOC multilayer thin films were grown via magnetron sputtering with controlled length scales on a surface-oxidized Si (100) substrate. These Fe/SiOC multilayers were in situ or ex situ annealed at temperature of 600 °C or lower. The thin multilayer sample (~10 nm) was observed to have a layer breakdown after 600 °C annealing. Diffusion starts from low groove angle triple junctions in Fe layers. In contrast, the thick multilayer structure (~70 nm) was found to be stable and an intermixed layer (Fe_xSi_yO_z) was observed after 600 °C annealing. The thickness of the intermixed layer does not vary as annealing time goes up. The results suggest that the Fe_xSi_yO_z layer can impede further Fe, Si and O diffusion, and assists in maintaining morphological stability.     

Magnetism of a cobalt-gold planar nanostructure on the silicon surface

The structural and magnetic properties of a cobalt nanolayer placed between a silicon substrate and a protective gold layer are studied. At a cobalt layer mass thickness of 1–2 nm, a nanoisland structure is shown to form. This thickness range is characterized by a local maximum of the magnetooptical Kerr effect and enhanced nonlinear optical and magnetic nonlinear optical responses at the second-harmonic frequency. This enhancement can be caused by the excitation of local surface plasmons and an increase in the local fields at the probing-radiation and second-harmonic frequencies in metallic nanoislands. The surface-sensitive nonlinear magnetooptical Kerr effect at the second-harmonic frequency is maximal at a cobalt layer thickness of about 2 nm, which corresponds to the characteristic scale of magnetization formation in the near-surface layer in cobalt.     

The superstructures of the clean Pt(100) and Ir(100) surfaces

The clean and reconstructed surfaces of Pt(100) and Ir(100) were investigated by low energy electron diffraction (LEED). It is shown that two superstructures can be observed in the case of platinum. The structure Pt(100)-hex, which is commonly called Pt(100)-(5 × 20), transforms to Pt(100)-hex-R0.7° above 1100 K. It is shown that this stable phase differs from the first one by a slight rotation of the hexagonal surface layer by 0.7°. For Ir(100) only the well known (1 × 5) superstructure is observed without any rotation of the outer layer. The rotation angle of 0.7° for platinum and the stability of the unrelated structure for iridium can be interpreted by simple calculations of the coordination of surface atoms with those of the second layer. The method assumes that the surface layer is of ideal hexagonal structure in the case of platinum and nearly hexagonal in the case of iridium. The results are in good agreement with the experiment.     

Genetic optimization of magneto-optic Kerr effect in lossy cavity-type magnetophotonic crystals

We have demonstrated an optimization approach in order to obtain desired magnetophotonic crystals (MPCs) composed of a lossy magnetic layer (TbFeCo) placed within a multilayer structure. The approach is an amalgamation between a 4×4 transfer matrix method and a genetic algorithm. Our objective is to enhance the magneto-optic Kerr effect of TbFeCo at short visible wavelength of 405 nm. Through the optimization approach, MPC structures are found meeting definite criteria on the amount of reflectivity and Kerr rotation. The resulting structures are fitted more than 99.9% to optimization criteria. Computation of the internal electric field distribution shows energy localization in the vicinity of the magnetic layer, which is responsible for increased light-matter interaction and consequent enhanced magneto-optic Kerr effect. Versatility of our approach is also exhibited by examining and optimizing several MPC structures.     

Local field effects in magneto-optics of two-dimensional arrays of ferromagnetic nanoparticles

A theory of the polar magneto-optical Kerr effect in a layer of small ferromagnetic particles has been developed in the framework of the Green’s function method of electrodynamics. The manifestation in magneto-optics of the local field effect, which is initiated by the contribution to the effective field of dipole moments induced in particles, has been studied in terms of the model of a square lattice of ferromagnetic ellipsoids. The magneto-optical Kerr effect stimulated under normal incidence of a linearly polarized electromagnetic wave on a layer of particles magnetized perpendicular to the layer plane has been analyzed. The dependence of the Kerr rotation angle in an array of ellipsoidal Co particles embedded in the transparent dielectric CaF₂ on the light frequency, the parameters of the ellipsoidal particles, and the lattice period (concentration of the magnet in the layer) has been studied numerically. It has been shown that, within a broad (2.0–4.5 eV) spectral range, the local field effect studied as a function of increasing concentration of Co particles in the layer manifests itself in the reversal of the sign of the Kerr rotation compared to that observed in a single ellipsoid or a solid Co film.     

Photonic-crystal properties of a 1D longitudinally magnetized periodic structure

Features of propagation of circularly polarized waves in a plane-layer periodic longitudinally magnetized ferromagnet—dielectric structure are studied. Dispersion relations and reflection coefficients are obtained, and frequency dependences of the Bloch wavenumber and reflection coefficients are constructed for natural waves of the periodic structure under investigation. The dependences of the polarization plane rotation angle in the polar Kerr effect on the frequency and the ratio of the thicknesses of layers over a period are constructed for various numbers of periods in the structure.     

非周期多层膜Kirkpatrick-Baez显微镜成像

从光线传播的角度分析了非周期多层膜Kirkpatrick-Baez(KB)显微镜的成像性能,并与单层膜KB显微镜、周期多层膜KB显微镜进行了对比。与单层膜KB显微镜相比,多层膜KB显微镜提高了工作掠入射角度,在同样分辨力和集光效率要求下具有更大的视场。周期多层膜KB显微镜的反射率和能量分辨本领高于非周期多层膜KB显微镜,但非周期多层膜元件具有较大的角度带宽和均一的反射率,克服了周期多层膜KB显微镜视场范围和像场均匀性的不足。在此基础上,制备了中心角度1.133 0°的非周期多层膜反射镜元件,以8 keV能量的X射线光管为背光源进行了KB显微镜成像实验,实验结果与理论分析一致。