Characterization of magnetic colloids by means of magnetooptics

A new, efficient method for the characterization of magnetic colloids based on the Faraday effect is proposed. According to the main principles of this technique, it is possible to detect the stray magnetic field of the colloidal particles induced inside the magnetooptical layer. The magnetic properties of individual particles can be determined providing measurements in a wide range of magnetic fields. The magnetization curves of capped colloids and paramagnetic colloids were measured by means of the proposed approach. The registration of the magnetooptical signals from each colloidal particle in an ensemble permits the use of this technique for testing the magnetic monodispersity of colloidal suspensions.     

Untersuchungen zur Temperaturabhängigkeit der Bereichstrukturen stabförmiger Nickel-Einkristalle

The domain structure of nickel single crystals of prismatic form and with a simple “two phase” basic structure has been investigated by using the magnetooptical Kerr technique. Observations of the periodical basic structure and of the closure domains on the side faces and their dependence on temperature are reported for the idealized and hysteresis curve. The results are compared with those of domain theory. Some discrepancies in the temperature dependence in weak fields and the interpretation of the Kerr pattern we believe to decrease if the model for the closure domains will be modified, especially by using an echelon structure and by modifying the stray fields.     

Magnetooptical images of inhomogeneous magnetic fields in metallic films with in-plane anisotropy

The magnetooptical (MO) images of the inhomogeneous field created by permanent magnets in magnetic metallic films with in-plane anisotropy are experimentally studied. The MO images recorded using the longitudinal Kerr effect are the superposition of two pictures, namely, a polar-sensitivity MO image and a longitudinal-sensitivity MO image. An analysis of these images after separation shows that the polar-sensitivity MO image reflects the distribution of the inhomogeneous field component that is normal to the surface of an indicator film in an analog manner. The longitudinal-sensitivity MO image reflects the angular distribution of the in-plane component of a stray field in an analog manner. The coincidence of the experimental and corresponding simulated MO images makes it possible to interpret the experimental images. In particular, it is shown that the specific features detected in the topological characteristics of the inhomogeneous field correspond to experimental singular points. Hidden magnetic images (magnetic bar codes) are shown to be visualized with metallic CoFe films. As an example, the stray field of a magnetic system made of cylindrical magnets is mapped.     

Peculiarities of permalloy thin film microcore hysteretic magnetization process in high space resolution fluxgate device

Magnetization processes of the sectioned thin film permalloy core were examined in relation with its geometrical dimensions using magnetooptical Kerr technique and ferrofluid observation. It is shown quantitatively the intermediate case between Stoner–Wohlfarth and zero internal field contradicting models takes place. Ferrofluid investigation had shown the stable quasi-saturated state with closing domain structures at permalloy bar edges. Magnetization reversal occurs by hysteretic manner but the hysteresis loop parameters are reproducible and depend strongly upon core geometry. Hysteresis is characterized by parallelogram form with clear critical field and loop slope depending on bars dimensions and their mutual position in array. Loop shape approaches the rectangular form and critical field increases if bar thickness t, width w and bar density in array are decreased. The critical field value H_cr is defined by demagnetizing field at bar edges while the saturation field H_s depends only on width w at of a bar in array. Variation of the bar form or shift of every second bar in array possesses to increase the core thickness to enhance the stray field without increase of the saturating exciting current. The core described can be used with magnetooptical garnet film or Hall sensor in fluxgate regime for magnetic field measurement with space resolution 10–100 mcm.     

Magnetooptical properties of Co-SiO<Subscript>2</Subscript> granular films

The structural, optical, and magnetooptical properties of Co-SiO₂ granular films are studied. It is found that the magnetooptical response is considerably enhanced in samples with a metal component concentration close to the percolation threshold. The Co nanogranules formed in the SiO₂ matrix exhibit ferromagnetic properties and are ordered into the fcc structure, which is confirmed by magnetooptical investigations. The magnetooptical properties of nanocomposites are simulated in the effective-medium approximation. It is shown that the singularities found in the magnetooptical spectra are related to the excitation of plasmon resonances in granular films.     

利用磁光效应测电流

本文介绍了一种磁光电流传感器的测试原理和实验方法，并对ＫＣ１饱和溶液和ＹＩＧ固体薄膜的磁光特性进行了分析。     

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。     

Enhancement of the Kerr effect in magnetooptical DyFeCo/GeO carriers

The optimum parameters of a dielectric layer near the substrate in the interference multilayer structure are calculated. The calculations showed that this layer should have the index of refraction n∼3. The results are presented of measuring the Kerr angle of magnetooptical rotation in the multilayer structure, in which GeO films were used as dielectric layers for the first time. The maximum Kerr angle of rotation and magnetooptical quality observed in this system were 0.75° and 0.34°, respectively. These values exceed those inherent in the known information carriers, which demonstrates the advantage of this structure for use in magnetooptical discs.     

Magnetooptical Kerr effect in the near field of a nanowire supporting surface plasmons

In terms of Green’s functions, a theory is developed describing the resonant magnetooptical Kerr effect in light scattering by a linear probe that is parallel to the surface of a magnet and placed at a subwavelength distance from it. The probe is supposed to be a metal nanowire supporting long-lived surface plasmons and forming the near field of the “probe + image” complex. The resonant interaction between the probe and the sample is taken into account within a self-consistent approximation of multiple-scattering theory, and the magnetooptical interaction is included in the linear approximation in magnetization. The problem of scanning near-field magnetooptical microscopy with a linear probe is solved analytically in the case where the magnetization is parallel to both the magnet surface and the plane of incidence of light (longitudinal magnetooptical Kerr effect). The polarization, spectral, and angular characteristics of scattered light modulated by magnetization are discussed. It is shown that the magnetooptical modulation of the scattered light intensity is significantly enhanced when surface plasmons are resonantly excited in the nanowire.     

榕树型互连网络及光学实现

讨论了一种用扭曲向列相液晶器件和偏振分光棱镜实现光学榕树上互连网络的结构，这种结构具有直线式传输、无错位、无缩放，并能够实现模块化和集成化的优点。     

Magnetooptische und optische Eigenschaften von ferromagnetischen Schichten im Ultraroten

The rotation of the plane of polarisation and the ellipticity of the reflected light at both sides and the transmitted light through magnetically saturated evaporated layers (30 mμ) of iron, cobalt and nickel are measured in the near I.R. and the visible spectrum (2·5 to 0·43 μ). The four measured magnetooptical angles are dependent one another according to the theory ofVoigt. They are found independent however each other. That can be explaned only by a magnetooptical term in the second equation of Maxwell too, if the layers are homogenous. This term is calculated and gives rise to a considerable portion of the magnetooptical effects. The transmitted light gains a rotation and ellipticity not only in the interior of the metal but also on the surfaces. This surface-change surpasses that in the interior in the I.R. region. It can be determined by extrapolating on the thickness zero or by calculating out of the measured Kerr-effect. Both methods agree well. This is a convincing prove that non-magnetical surface-layers are there not existing. The magnetooptical rotation of Nickel has a sharp peak at 1 μ, the other magnetooptical constants, include the calculated magnetical terms show a more monotonous course with the wavelenght, also for the other metals. The optical constants are determined by measurements of intensity of the reflected light on both sides of the layer and of the transmitted light.     

双光束磁光存贮中信号读出的偏振态分析

利用琼斯矩阵分析了双光束磁光存贮中信号读出系统偏振态的传输情况，推导了读出信号的表达式，分析了偏振分束镜与光盘盘基的相位延迟对读出信号的影响。     

Analysis of Different Contributions into the Magnetooptical Signal of Magnetophotonic Crystal Type Three-Dimensional Structures

Interference of effects of different levels and magnitudes in producing a net magnetooptical response was considered for the first time in structures similar to magnetophotonic crystals at different wavelengths of the incident irradiation in regions far from plasmon resonances. Contributions of interference and diffraction phenomena in maxima of different orders in three-dimensional systems of the magnetophotonic crystal type were studied. Use of the integral response in the analysis of the magnetooptical effects was shown to lead to disappearing of the interference phenomena. The zero-order diffraction maximum reflects adequately the magnetic component of the magnetooptical response. Numerical estimates of the observed diffraction and interference effects are reported.     

IV–VI compound compositional and doping superlattices

Structural, electronic, optical and magnetooptical investigations on compositional superlattices (mainly PbTe/PbSnTe, PbTe/PbEuSeTe) are summarized. Recent results on transport and magnetooptical effects in PbTe doping superlattices are presented and examples for an excellent photoconductivity response of these structures in the 5μm region are given.     

Theory of magnetooptical effects in thin ferromagnetic films

A systematic theory is derived for the anomalous magnetooptical effects in thin ferromagnetic films for the more general case in which conduction electrons are scattered by both phonons and impurities. The Kohn-Luttinger density-matrix method is used to find the tensor for the complex transverse conductivity, which is linear in the spin-orbit interaction and can be used to find the magnetooptical parameter. The temperature dependences of the real and imaginary parts of the conductivity tensor are found for high temperatures.     

Features of two-photon resonances of nonlinear magnetooptical rotation of the plane of polarization for the initial population of fine-structure levels in alkali atoms

The features of nonlinear magnetooptical effects of fine-structure levels of an alkali atom, including effects in strong magnetic fields, as well as under conditions of two-photon resonance, are considered. The spectra of magnetooptical rotation and of magnetic circular dichroism have been obtained for the first time for the nontrivial initial population of magnetic sublevels of excited electronic states of an alkali atom, as well as under conditions of two-photon resonance. The decrease in the amplitude of resonances of initially populated fine-structure levels is explained by population transfer, taking place in strong fields. This transfer affects the rotation of the plane of polarization. The lower the initial population, the more pronounced the population transfer. Numerical experiments have shown that analysis of the resonance shapes in the spectra of magnetooptical rotation can yield information on the initial population of magnetic sublevels of excited electronic states of atoms.     

Reflection and transmission of light by a ferromagnetic structure with a noncollinear orientation of the magnetization of layers

The transmission and reflection of light by a ferromagnetic structure with a noncollinear orientation of the magnetization vectors of layers lying in the plane of the film is considered. The characteristic matrix of the structure that relates the wave amplitudes at the entrance to the system and at the exit from it and that determines the magnetooptical properties of the structure is calculated. The magnetooptical characteristics of this structure are shown to significantly depend on the angle between the magnetization vectors of layers and on the number of layers. Both the magnitude and the character of these dependences are analyzed in relation to the angle of incidence and to the polarization of the incident wave. Such an analysis makes it possible to optimize the magnetooptical properties of this structure.     

Magnetooptical effects in ferromagnetic metals at low temperatures

Zeroth-order and first-order Boltzmann kinetic equations are found for the frequency-dependent transverse-conductivity tensor for inelastic scattering of electrons, with an account of thermal oscillations of the scattering centers. At low temperatures this tensor, which is linear in the spin-orbit interaction, depends exponentially on the temperature. A relation is found between the magnetooptical effects in ferromagnetic metals and the topology of the Fermi surfaces; from this relation, qualitative conclusions can be drawn regarding the effect of this topology on the magnetooptical effects and regarding the sign of the anomalous magnetooptical parameter (which depends on whether hole or electronic conductivity predominates).Translated from Izvestiya VUZ. Fizika, No. 4, pp. 86–90, April, 1970.     

The possibility of measuring linear and quadratic magnetooptical effects in magnetic field under conditions of magnetomechanical resonance

We have considered the possibility of measuring the linear and quadratic (in magnetic field) magnetooptical effects in magnetooptical crystals that are simultaneously exposed to a constant (polarizing) magnetic field and to an alternating magnetic field under conditions of magnetomechanical resonance. The use of a Mueller polarimeter in combination with spectral analysis of the intensity of the light wave at the output of the polarimeter makes it possible to selectively determine elements of the Mueller matrix and minimize the amount of measurements. We have shown that there is a possibility of solving the inverse problem on finding two components of the alternating magnetic field in which a magnetooptical crystal is placed.     

Theory of scanning near-field magnetooptical microscopy

An analytical theory of scanning near-field magnetooptical microscopy is developed. The theory is based on the elastic scattering of light by small, resonantly polarizable particles, which are used to scan the plane surface of a nonuniformly magnetized medium. The effective polarizability of the particles is calculated with the effect of dynamic “image forces” taken into account in all orders of perturbation theory with respect to the interaction of the particle with a demagnetized ferromagnet, and the magnetooptical perturbation is calculated to first order in the magnetization. The major contributions to the magnetooptical light scattering for a ferromagnetic structure magnetized perpendicular to the surface are found, including a quasistatic approximation for the near-field particle-magnet interaction. The optical size resolution of a magnetic (dielectric) inhomogeneity is estimated. Zh. Tekh. Fiz. 68, 86–91 (July 1998)