自然旋光与法拉第效应的实验研究

介绍了自然旋光与法拉第效应偏转角的测量方法,讨论了两种效应下偏转角的影响因素,说明了两种效应的应用领域。由分析得到:自然旋光偏转角的大小只与晶体有关,与磁场无关,而旋光方向与光的传播方向有关;法拉第效应偏转角的大小正比于磁感应强度,其偏转角旋光方向只与磁场方向有关,与光的传播方向无关;光往返通过自然旋光晶体时,偏转角相互抵消,磁致旋光晶体偏转角则实现累加。利用晶体的法拉第效应,可将其制成光学隔离器或单通光闸等器件。     

A Scanning Magnetooptical Micromagnetometer

A scanning magnetooptical magnetometer designed for measuring weak spatially nonuniform magnetic fields is described. The magnetometer's principle of operation is based on the Faraday effect caused by the magnetic field under study in the region of an epitaxial garnet-type ferrite film whose dimensions are on the order of the period of its domain structure. The magnetic-field sensitivity of the designed magnetometer is about 3 × 10⁻³ Oe for a spatial resolution of about 20 μm. __________ Translated from Pribory i Tekhnika Eksperimenta, No. 5, 2005, pp. 107–110. Original Russian Text Copyright ? 2005 by Vil'danov, Sokolov.     

BBO晶体中的级联二阶过程和三阶光学非线性效应

本文讨论了非线性光学晶体中的级联二阶过程。在小信号转换近似下,这一过程被公式化,由三阶非线性极化率表示。作为比较,用自位相调制和光学混频方法,研究了BBO晶体的级联二阶过程。发现由于这一过程的存在,该晶体的三阶非线性被明显增加,极化率达10^-19m²/V².     

Measurement of magnetic susceptibility in pulsed magnetic fields using a proximity detector oscillator

We present a novel susceptometer with a particularly small spatial footprint and no moving parts. The susceptometer is suitable for use in systems with limited space where magnetic measurements may not have been previously possible, such as in pressure cells and rotators, as well as in extremely high pulsed fields. The susceptometer is based on the proximity detector oscillator, which has a broad dynamic resonant frequency range and has so far been used predominantly for transport measurements. We show that for insulating samples, the resonance frequency behavior as a function of field consists of a magnetoresistive and an inductive component, originating, respectively, from the sensor coil and the sample. The response of the coil is modeled, and upon subtraction of the magnetoresistive component the dynamic magnetic susceptibility and magnetization can be extracted. We successfully measure the magnetization of the organic molecular magnets Cu(H(2)O)(5)(VOF(4))(H(2)O) and [Cu(HF(2))(pyz)(2)]BF(4) in pulsed magnetic fields and by comparing the results to that from a traditional extraction susceptometer confirm that the new system can be used to measure and observe magnetic susceptibilities and phase transitions.     

High temperature faraday balance for in situ measurement of magnetization in transition metal oxides

We report the design of a Faraday balance that can be used to measure the magnetization of transition metal oxides at high temperatures and under controlled atmosphere. The instrument is sufficiently sensitive and stable to quantify the magnetic force on diamagnetic and paramagnetic samples at temperatures up to 1000 degrees C and in oxygen partial pressures as low as 100 ppm. We demonstrate the performance of the instrument by presenting preliminary magnetic measurements of lanthanum strontium cobalt oxide (La1-xSr(x)CoO3-delta) and aluminum oxide (Al2O3).     

CCD磁动式氧含量分析仪的分析与设计

介绍常见气体磁化率，利用氧气顺磁性，且磁化率明显高于其它气体的物理特性，分析磁动式测量混合气体中氧气含量的方案。通过在非均匀磁场悬挂一对充氮玻璃小球构成测量池；采用光杠杆对哑铃球扭转的角度信号进行放大，由CCD对光点位置信号进行探测，以提高分析仪灵敏度和精度；由NO、NO2的磁化率特性分析这两种气体对分析仪的影响，说明测氧仪的应用环境。通过对CCD像元值随气体氧含量、温度变化规律的分析，得出分析仪的分辨率可达0．048％以上；CCD像元值随氧含量变化、随温度变化基本呈线性关系，数据处理后可使仪器有较高的精度。     

Torque detected broad band electron spin resonance

We present a novel technique to measure high frequency electron spin resonance spectra in a broad frequency range (30-1440 GHz) with high sensitivity. We use a quasioptical setup with tunable frequency sources to induce magnetic resonance transitions. These transitions are detected by measuring the change in the magnetic torque signal by means of cantilever torque magnetometry. The setup allows tuning of the frequency, magnetic field, polarization, and the angle between the sample and the external magnetic field. We demonstrate the capabilities of this technique by showing preliminary results obtained on a single crystal of an Fe(4) molecular nanomagnet.     

Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range

A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01-1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low frequencies make it possible to study the rotational dynamics of large magnetic colloidal particles or aggregates dispersed in a liquid. The distinguishing features of the setup are the novel multilayered cylindrical coils with a large sample volume and a large number of secondary turns (55 000) to measure induced voltages with a good signal-to-noise ratio, the use of a dual channel function generator to provide an ac current to the primary coils and an amplitude- and phase-adjusted compensation voltage to the dual phase differential lock-in amplifier, and the measurement of several vector quantities at each frequency. We present the electrical impedance characteristics of the coils, and we demonstrate the performance of the setup by measurement on magnetic colloidal dispersions covering a wide range of characteristic relaxation frequencies and magnetic susceptibilities, from chi approximately -10(-5) for pure water to chi>1 for concentrated ferrofluids.     

Measuring magnetic susceptibilities of nanogram quantities of materials using microcantilevers

We describe a novel technique for measuring magnetic susceptibilities of nanogram quantities of magnetic materials that utilizes the extreme force sensitivity of microcantilevers. The magnetic force acting on samples attached to the free end of a cantilever can be measured as changes in the resonance response of the cantilever. The shift in resonance frequency of the cantilever is proportional to the field gradient, whereas the deflection of a cantilever is proportional to the magnetic force. The magnetic susceptibility measurement is based on comparison of the forces acting on the sample and a reference material in the same magnetic field and field gradient. We have determined the magnetic susceptibilities of nanogram quantities of many paramagnetic materials. The measured magnetic susceptibilities show excellent agreement with values found in the literature.     

Effect of Magnetic Field Dynamics on the Copper‐Constantan Thermocouple Performance

Abstract

This paper presents some results of experimental research addressing the influence of magnetic field dynamics on the copper‐constantan thermocouple performance. There are challenges in measuring temperature by thermocouples in a time‐dependent magnetic field. Although there is considerable experience on the effect of a static magnetic field, there is a lack of awareness of the outcome of a varying field on thermocouple performance. We measured the accuracy of the thermocouple response in an alternating magnetic field for various operational parameters: frequency of the magnetic field, geometry, and length of the thermocouple wire in the field, and magnetic field strength. The effect of each of the operational parameters is discussed. Test results of temperature profile measure by a copper‐constantan thermocouple in a varying magnetic field system that was used in a room temperature magnetic refrigeration test bed are demonstrated.     

Charged fusion product loss measurements using nuclear activation

In ITER, α particle loss measurements will be required in order to understand the alpha particle physics. Techniques capable of operating in a fusion reactor environment need further development. Recent experimental studies on JET demonstrated the potential of nuclear activation to measure the flux of escaping MeV ions. New results from MeV ion induced activation of metallic, ceramic, and crystal samples placed near the plasma edge are reported. Activation products were measured as function of orientation with respect to the magnetic field as well as function of the distance to the plasma. Sample activity was measured using ultralow-level gamma-ray spectrometry. Distribution of 14.68 MeV fusion proton induced activation products is strongly anisotropic in agreement with simulations and falls off sharply with increasing distance to the plasma. Prospects for using the technique in ITER are discussed.     

Development of the caliper system for a geometry pig based on magnetic field analysis

This paper introduces the development of the caliper system for a geometry PIG (Pipeline Inspection Gauge). The objective of the caliper system is to detect and measure dents, wrinkles, and ovalities affect the pipe structural integrity. The developed caliper system consists of a finger arm, an anisotropic permanent magnet, a back yoke, pins, pinholes and a linear hall effect sensor. The angle displacement of the finger arm is measured by the change of the magnetic field in sensing module. Therefore the sensitivity of the caliper system mainly depends on the magnitude of the magnetic field inside the sensing module. In this research, the ring shaped anisotropic permanent magnet and linear hall effect sensors were used to produce and measure the magnetic field. The structure of the permanent magnet, the back yoke and pinhole positions were optimized that the magnitude of the magnetic field range between a high of 0.1020 Tesla and a low of zero by using three dimensional nonlinear finite element methods. A simulator was fabricated to prove the effectiveness of the developed caliper system and the computational scheme using the finite element method. The experimental results show that the developed caliper system is quite efficient for the geometry PIG with good performance.     

基于锁相技术和磁光调制的旋光角度检测

根据法拉第磁光效应和锁相基本原理,研究了经磁光调制后的偏振光通过旋光物质后的偏转情况,分析了透射光信号中的与调制频率相同的基频信号和二倍于调制频率的倍频信号。通过对基频幅值和倍频幅值进行比较,提出了一种测量旋光角度的计算方法,根据旋光角和磁偏角两者之间的关系,提出了一种用标准石英管来标定法拉第磁光效应中磁偏角大小的方法,并对其进行了实验研究,证明了这种测量方法的可行性。     

纳米尺度单晶铜材料表面切削特性分子动力学模拟

采用分子动力学模拟方法研究单晶铜材料表面纳米切削特性。通过对单晶铜纳米切削过程进行分子动力学建模、计算与分析,研究了不同切削速度及切削厚度对单晶铜材料表面纳米切削过程中微观接触区域原子状态和切削力变化的影响规律。研究结果发现：在单晶铜表面纳米切削过程中,切削速度越高,切屑堆积体积越大,切屑里原子的排列越紧密,位错缺陷分布区域越大;在同种切削速度下,切削厚度越大,在刀具前方堆积的切屑体积越大,位错缺陷越多。不同切削速度及切削厚度下,切削力曲线均在切削初期呈上升趋势,达到稳定切削状态后围绕稳定值进行波动,但在切削初期,切削速度及切削厚度越大,切削力上升幅度越大;达到稳定切削状态后,切削速度、切削厚度越大,切削力越大。     

Magnetization and magnetoresistance of common alloy wires used in cryogenic instrumentation

We present magnetization and magnetoresistance data at liquid-helium and liquid-nitrogen temperatures for wire materials commonly used for instrumentation wiring of specimens, sensors, and heaters in cryogenic probes. The magnetic susceptibilities in Systeme International units at 4.2 K were found to be: Manganin 1.25x10(-2), Nichrome 5.6x10(-3), and phosphor bronze -3.3x10(-5), indicating that phosphor bronze is the most suitable for high-field applications. We also show the ferromagnetic hysteresis loop of Constantan wire at liquid-helium temperature. The magnetoresistance of these four wires was relatively small: the changes in resistance at 4 K due to a 10 T transverse magnetic field are -2.56% for Constantan, -2.83% for Manganin, +0.69% for Nichrome, and +4.5% for phosphor bronze, compared to about +188% for a typical copper wire under the same conditions.     

A magnetometer of weak quasi-stationary and high-frequency fields on resonator microstrip transducers with thin magnetic fields

A high-sensitivity magnetometer for simultaneous measurements of three components of a weak quasi-stationary or high-frequency magnetic-field vector was developed and investigated. Microstrip structures that are based on irregular resonators serve as the magnetometer transducers. An anisotropic thin-film magnetic structure is used as the sensing element. This structure consists of two thin magnetic films that are prepared by magnetron sputtering of a Ni₇₅Fe₂₅ permalloy target and separated by a silicon monoxide layer. It is demonstrated that the transducer exhibits the maximum sensitivity, when the easy magnetization axis of the film structure is orthogonal to the polarization direction of the pumping microwave magnetic field in the microstrip resonator and at an optimal value of a constant magnetic bias field and its optimal deflection from the pumping-field polarization direction which is parallel to it. The magnetometer is characterized by a wide dynamic range of measured magnetic fields, 10^–10–10^–4 Т, and a wide frequency range, 10^–1–10⁵ Hz.     

采用多层膜偏光器的EUV实验室Farady旋光测量装置

开发了用于实验室的ＥＵＶ（５０～７０ｅＶ）波段的Ｆａｒａｄａｙ 旋光测量装置。其中光源采用了激光等离子体光源。起偏器和检偏器均采用了入射角为准Ｂｒｅｗ ｓｔｅｒ角的反射式Ａｌ／ＹＢ６多层膜。利用４ 块Ｓｍ －Ｃｏ 永久磁铁在被测样品处生成了０．８２Ｔ的磁场。对强磁材料Ｎｉ的Ｍ２,３吸收端进行了Ｆａｒａｄａｙ 旋光测量,测量结果在６５．３ｅＶ处为－ ２．７°／２１ｎｍ 。该结果与我们在同步辐射光源上测量的结果相符合。这是ＥＵＶ 波段首次利用激光等离子体光源成功进行的磁光效应测量实验。     

用溶胶—凝胶方法制备磁光记录用的铋代钇铁石榴石薄膜

研究了在ＧＧＧ基底上用溶胶—凝胶方法制备的铋代钇铁石榴石单晶薄膜的磁光法拉弟效应与铋的替代量之间的关系。该膜层是以低于液相外延３００℃左右的６６０℃在大气中退火４ 小时制得的。最大的铋的置换量为ｘ＝ ２．７,实验发现石榴石相的晶化温度随ｘ 的增大而降低。且薄膜有很强的法拉弟效应,在λ＝ ０．６３３μｍ 的波长,可达－ ８．１×１０４ｄｅｇ／ｃｍ 。     

Faraday rotation data analysis with least-squares elliptical fitting

A method of analyzing Faraday rotation data from pulsed magnetic field measurements is described. The method uses direct least-squares elliptical fitting to measured data. The least-squares fit conic parameters are used to rotate, translate, and rescale the measured data. Interpretation of the transformed data provides improved accuracy and time-resolution characteristics compared with many existing methods of analyzing Faraday rotation data. The method is especially useful when linear birefringence is present at the input or output of the sensing medium, or when the relative angle of the polarizers used in analysis is not aligned with precision; under these circumstances the method is shown to return the analytically correct input signal. The method may be pertinent to other applications where analysis of Lissajous figures is required, such as the velocity interferometer system for any reflector (VISAR) diagnostics. The entire algorithm is fully automated and requires no user interaction. An example of algorithm execution is shown, using data from a fiber-based Faraday rotation sensor on a capacitive discharge experiment.     

各向异性磁阻传感器的原理及其应用

详细介绍了各向异性磁阻传感器的物理机理，并以HMC1002为例说明其测量原理、芯片以及电路的主要特点，给出了弱磁测量的结果与分析。将HMC1001，HMC1002与倾角传感器相结合，可用于姿态的测量。并介绍了其在场源相关性识别中的作用和应用电路。分析了各项异性磁阻传感器的优点及前景预测。