软磁材料音频磁滞回线显示仪

本文介绍一种适用于大专院校演示实验和电磁学实验教学的磁测仪器,也可以用于生产厂家和科研单位。它与示波器配用可以在荧光屏上显示软磁材料的动态磁滞回线,以及磁场强度波形、磁感应强度波形、感应电动势波形等。由饱和磁滞回线经仪器内定标之后可以定量计算饱和磁感应强度B_s、剩余磁感应强度B_r、达到饱和时的磁场强度H_s以及矫顽力H_e等磁性参量。相对误差<7%,所用样品平均直径1cm相似文献   

李萨如图形法测量软磁材料磁导率

提出了李萨如图形的一个新应用——测量软磁材料磁导率.实验系统由示波器和信号发生器构成,以安培环路定理及法拉第电磁感应定律为理论基础,利用李萨如图形实现了软磁材料磁导率的测量.实验结果给出了在材料未达到饱和磁化的情况下,不同励磁频率下的磁导率测量结果.     

磁场强度H与磁介质无关的充要条件及其应用

推导出磁场强度H与磁介质无关的充要条件，获得了一种计算有介质存在时磁感应强度B分布的简单方法．     

磁场强度波形畸变对交流磁滞回线形状的影响

测量了软磁铁氧体环形样品在不同条件下的交流磁滞回线,发现磁滞回线形状随交流磁场强度H的幅值、频率而变化.交流磁滞回线形状的变化是由于磁场强度H波形畸变造成的,在弱交变场下,当磁感应强度B作正弦变化时,磁场强度H也作正弦变化,此时磁滞回线形状为椭圆;当磁场增强时,H-t曲线发生了不同程度畸变,且磁场强度越强,H-t曲线畸变程度越严重,此时磁滞回线变弯变尖,呈胖S形.通过理论分析及实验拟合对磁滞回线形状变化做出了解释.     

用数字电桥测量介电材料与软磁材料的特性

应用数字电桥采用并联等效或串联等效方法测量了介电材料和软磁材料的特性,考察了BaTiO_3材料的复电容率及MnZn铁氧体材料的复数磁导率随频率的变化规律.     

基于铁氧体基板的开口谐振环的可调微波左手特性研究

利用铁氧体的外场调制特性,提出采用铁氧体作为金属环线结构的介质基板,实现频率可调左手材料. 首先采用时域差分有限元方法数值模拟了基板材料参数变化的条件下,开口谐振环的频率可调性规律. 随基板材料的介电常数或磁导率升高,与开口谐振环负磁导率对应的透射谷频率将显著降低. 实验制备了一系列超高频软磁六角铁氧体,利用外加磁场有效调制了其磁导率. 并通过实验表明,通过调控外加磁场可以有效地调控开口谐振环负磁导率对应的透射谷频率. 关键词： 左手材料 开口谐振环 铁氧体 可调     

蜂窝结构吸波材料等效电磁参数和吸波特性研究

根据强扰动理论,在长波长近似条件下推导出蜂窝结构吸波材料等效介电常数和等效磁导率的计算公式.电磁参数计算结果表明,蜂窝结构吸波材料等效介电常数和等效磁导率均小于吸收层的介电常数和磁导率,但等效介电常数的降幅更大,从而使等效介电常数更接近于等效磁导率,这正是吸波材料波阻抗匹配设计所需要的.反射率计算结果表明,不同的蜂窝高度,吸收层对应一最优厚度,使蜂窝结构吸波材料的反射率最低.这些结果对于蜂窝结构吸波材料设计具有一定的意义. 关键词： 蜂窝结构吸波材料 等效介电常数 等效磁导率 反射率     

磁化铁氧体材料电磁散射递推卷积-时域有限差分方法分析

根据递推卷积原理，将磁化铁氧体材料的频域磁导率过渡到时域，通过引入时域复数磁化率张量和时域复数磁感应强度矢量，提出了磁化铁氧体材料电磁散射的三维时域有限差分方法.为了验证该方法，用它计算了磁化铁氧体球的后向雷达散射截面，与文献结果符合很好.计算结果表明，该方法是分析磁化铁氧体材料电磁散射一种可行的方法. 关键词： 递推卷积 磁化铁氧体 电磁散射 时域有限差分方法     

Fe-Ga磁致伸缩材料的磁学特性研究

通过电阻应变片法得到其磁致伸缩系数随磁感应强度的变化关系.由磁滞回线以及磁导率随磁场变化关系可以得到该Fe-Ga磁致伸缩材料为软磁材料,几乎没有剩磁、矫顽力.     

取向易面各向异性羰基铁粉体的高频磁性研究

研究了取向度对羰基铁粉体复合材料微波磁性的影响.理论上构造了取向片状磁性颗粒磁矩的高斯分布,并通过Landau-Lifshitz-Gilbert方程得到了有取向度的软磁材料复数磁导率的求解方法,模拟计算了羰基铁样品高频复数磁导率随频率的变化.研究发现:随着样品取向角?θ?的变大,高斯分布标准偏差σ减小,取向度f增大;随着片状样品取向度的提高,材料初始有效磁导率的实部值增大.为了对照,利用穆斯堡尔谱得到磁体的取向度,并通过网络分析仪测量了磁体的高频磁导率,所获得的实验结果与理论预期值相符.     

基于虚拟仪器技术的磁场的测量

以螺线管磁场测试仪为硬件基础,LabVIEW为软件支持,通过数据采集卡将两者结合,直接测得通电长直螺线管轴线上的磁场分布,实现了磁场的自动化测量。测试结果表明,不同励磁电流下,通电长直螺线管中部轴线上均为匀强磁场,且大小是端口处磁场的两倍。该方法原理直观明了,操作简单,可作为创新和研究型项目。     

Hysteresis loss reduction in self-bias FeSi/SrFe12O19soft magnetic composites

The magnetic field provided by magnetized SrFe₁₂O₁₉particles in FeSi/SrFe₁₂O₁₉composites is used to replace the applied transverse magnetic field,which successfully reduces the magnetic loss of the composites with minor reduction of permeability.This magnetic loss reduction mainly comes from the decrease in hysteresis loss,while the eddy current loss is basically unaffected.The hysteresis loss reduction in magnetized composites is believed to be due to the decrease in domain wall displacement caused by the increase in the average magnetic domain size in a DC magnetic field.This is an effective method for reducing the magnetic loss of soft magnetic composites with wide application potential,and there is no problem of increasing the cost and the volume of the magnetic cores.     

一种霍尔效应测量磁场的设计方法

针对大学物理实验中＂霍尔效应法测量磁场＂项目只能测长直螺线管轴线上一维稳恒磁场分布的不足,提出一种设计方法,来测量任一未知稳恒磁场的二维分布,进而可扩展到测量三维分布。可使学生深刻全面理解霍尔效应测磁场的原理及磁场的性质,并可作为设计性实验项目在大学物理实验课中开出,培养学生的创新意识。     

疏松载流螺线管轴线上磁场的分布研究

疏松载流螺线管轴线上磁场实验的设计可以测量螺线管轴线不同位置上的轴向磁场和径向磁场,实验结果与数值计算结果吻合。另外,从该实验测量结果发现疏松型螺线管轴线上的轴向磁场与螺距呈近似线性关系。这些工作不仅可作为大学物理实验课的选做内容,还可以为设计基于测量磁场的位移和应力传感器提供依据。     

用三角波电流励磁改进交流磁滞回线实验简

改进行了交流磁滞回线实验的励磁方法。研制了三角波电流交流恒流源驱动励磁线剖励磁．使软磁环形样品被交流磁化双向交替达到饱和,磁化场H的波形仍为三角波。维持三角波电流的周期和幅值不变．可使H变化的波形和变化的速率不变。可在H匀速变化的条件下观测样舳的交流磁滞回线;能在磁化场相同的条件下观测不同样品的交流磁滞回线;还可直接观测样品的微分磁导率曲线。     

求任意形状截面无限长直载流螺线管磁场的一种方法

在电磁学中,无限长直载流螺线管的磁场是一个基本与核心的问题,为了得到这一系统的磁场,通常的做法是：先就圆截面情况计算,然后把截面为任意形状无限长直螺线管看成是由无数大大小小的圆截面螺线管叠加而成,由此得到螺线管内的磁场均匀而管外磁场为零的一般结论.这里给出了一种推导截面为任意形状无限长直螺线管内外磁场的直接方法.先计算螺线管表面一窄条的磁场,再算总磁场.这种方法物理图像清楚,数学过程简单,可以在教学中加以应用.     

Magnetization Configuration in Magnetic Trilayer System with Out-of-Plane Component Defect

The equilibrium magnetization configuration, the inducing field and the coercive field in trilayer magnetic materials having an out-of-plane anisotropy defect interlayer between two in-plane anisotropy layers are discussed by both analytical and numerical calculations based on a micromagnet approach. It is shown that the above physical parameters strongly depend on the defect layer such as its thickness and exchange stiffness etc., as well as on the applied fields. It is found that there is a special thickness of defect layer, in which the inducing effect begin to occur, and the critical behavior of inducing field in the vicinity of the special thickness is linearly characterized. Particularly, the magnetic hysteresis shows typical soft hysteresis shape, even though the host material is composed of hard magnets, and the coercivity increases with increasing the thickness of the interlayer.     

Magnetic properties of Co-P-based trilayers

The magnetic properties of a film trilayer consisting of hard magnetic and soft magnetic Co-P layers separated by a nonmagnetic Ni-P spacer have been studied. The features of the hysteresis shift relative to the zero exchange magnetic field and of the coercivity of the soft magnetic layer in the dependence on thicknesses of the hard magnetic layer and spacer have been considered. The dynamic changes in the shift of the hysteresis of the soft magnetic layer versus the magnetization reversal time after saturation of the hard magnetic layer have been found and investigated.     

Thickness dependence of microwave magnetic properties in electrodeposited Fe-Co soft magnetic films with in-plane anisotropy

In this work, the thickness effect of Fe₅₂Co₄₈ soft magnetic films with in-plane anisotropy on static and microwave magnetic properties was investigated. The hysteresis loop results indicated that the static in-plane uniaxial anisotropy field increased from almost 0-60 Oe with increasing film thickness from 100 to 540 nm and well-defined in-plane uniaxial magnetic anisotropy can be obtained as the thickness reached 540 nm or larger. Based on Landau-Lifshitz-Gilbert (LLG) equation, the microwave complex permeability spectra were analyzed and well fitted. The LLG curve-fitting results indicated that the initial permeability increased from 106 to 142 and the resonant frequency was shifted from 4.95 to 4.29 GHz as the film thickness was varied from 540 to 1500 nm. Moreover, it was found that there was a discrepancy between the static and the dynamically determined anisotropy field, which can be explained by introducing an additional effective isotropic ripple field. The decreased ripple field was suggested to result in a significant decrease of damping coefficient from 0.109 to 0.038.