Magneto-impedance in glass-coated CoMnSiB amorphous microwires

A magneto-impedance (MI) effect has been experimentally detected and systematically studied in Co_68.5Mn_0.5Si₁₀ B₁₅ glass-coated amorphous microwire 14 μm in diameter. The dependence of MI on a dc applied magnetic field (up to 20 Oe) for a range of values of ac current (less than 4 mA and having a frequency between 0.2 and 2.0 MHz) flowing along the microwire has been measured in as-prepared samples, as well as after heat treatments up to 400°C. A maximum relative change in MI of around 16% is observed in the optimum conditions, that is, for about 5 Oe dc axial applied field and 3 mA, 2 MHz ac current flowing along the microwire, which finally corresponds to a magnetic field sensitivity of about 0.4 V/Oe. Such modifications are interpreted considering the dependence of the skin-effect on those parameters through the induced changes in the circular permeability. MI in these ferromagnetic wires with micrometric dimension is of technological interest for local detection of magnetic fields     

非晶FeSiB薄膜中的巨磁阻抗效应

采用射频溅射法在三组不同溅射条件下制备了FeSiB薄膜。测量了溅射薄膜的磁滞回线 ,并利用HP 41 94A阻抗分析仪 ,在 1～ 40MHz频率范围内研究了样品的巨磁阻抗效应。结果表明 :溅射条件对薄膜磁性能和巨磁阻抗效应影响很大 ,其中氩气压强为 6 65Pa ,磁场感生横向单轴磁各向异性的薄膜具有较好的软磁性能和较大的阻抗变化比值。一定温度下退火能够消除部分应力 ,阻抗变化的灵敏度能提高一倍。另外 ,对巨磁阻抗效应与测量磁场和薄膜易轴的相对位置取向之间的关系也作了讨论     

铁基巨磁阻抗薄膜的研究

溅射方法制备的非晶Fe68Cu0 .5Cr4 V5Si13 .5B9薄膜 ,通过适宜的退火处理得到具有纳米α Fe(Si)和非晶母相的混合结构和最佳的软磁性能 ,相应的巨磁阻抗值最高可达 72 %。本文着重研究了热处理条件、薄膜组织结构、软磁性能以及驱动电流频率对Fe68Cu0 .5Cr4 V5Si13 .5B9薄膜磁致阻抗的影响。     

FeSiB薄膜的巨磁阻抗和应力阻抗效应研究

软磁材料中存在巨磁阻抗 (giantmagneto impedance ,GMI)效应以及与之相同来源的应力阻抗 (stress impedance ,SI)效应 ,利用这两种效应可以制成具有高灵敏度的微型化的磁场和应力 应变传感器。本文基于传感器的实际应用 ,对图形化的、较大磁致伸缩的FeSiB单层和多层薄膜的巨磁阻抗和应力阻抗效应中频率和退火的影响进行了研究。结果表明 ,对于两种效应 ,经过退火处理的单层和多层膜均可在较低的频率下得到较高的灵敏度 ,而多层膜中的应力阻抗效应将为新型高灵敏传感器的设计和研制开辟一条崭新的途径     

FeSiB/Cu/FeSiB多层膜巨磁阻抗效应研究

用磁控溅射法在玻璃基片上制备了FeSiB/Cu/FeSiB多层膜,在100kHz～40MHz范围内研究了FeSiB/Cu/FeSiB多层膜中的巨磁阻抗效应特性.当磁场强度Ha施加在薄膜的长方向时,巨磁阻抗效应随磁场的增加而增加,在某一磁场下达到最大值,然后随磁场的增加而下降到负的巨磁阻抗效应.在频率为3.2MHz时,在磁场强度Ha=2400A/m时巨磁阻抗变化率达到最大值13.50%;在磁场强度Ha=9600A/m时,巨磁阻抗变化率为-9.20%.巨磁阻抗效应的最大值及负的巨磁阻抗效应与多层膜中磁各向异性轴的取向及发散有关.另外,当磁场施加在薄膜的短方向时,薄膜表现出负的巨磁阻抗效应,在频率为3.2MHz,磁场强度Ha=9600A/m时,巨磁阻抗变化率可达-12.50%.     

横向巨磁阻抗效应中磁导率张量的理论研究

建立了比较完善的二维铁磁体在横向巨磁阻抗 (GMI)效应中的磁化模型 ,采用将静态磁化过程和动态磁化过程分开计算的方法 ,同时考虑畴壁移动和磁畴转动两种磁化机制的影响 ,推导出比较完善的用于二维铁磁体横向巨磁阻抗效应理论研究的磁导率张量的表达式。     

电流退火NiFeCoP/BeCu复合结构丝的巨磁阻抗效应和磁化特性

用化学镀的方法制备了镀NiFeCoP膜的复合结构丝,这种复合结构丝在较低频率下就有较好的磁阻抗效应.对样品进行电流退火处理,不同电流密度退火对复合结构丝磁阻抗效应特性的影响不同.利用复数磁导率探讨了该复合丝在不同电流密度退火后的磁化过程和磁化频率特性,较大电流密度退火后复合结构丝的畴壁运动被抑制,减弱了动态磁化过程,降低了相应的磁阻抗效应.     

Magneto-inductive element

A novel sensitive magnetic head using a magnetoinductive (MI) effect in zero- or negative-magnetostrictive amorphous wires is described. The MI effect refers to the change of an inductance L for an external magnetic field in a ferromagnetic wire element magnetized with a wire AC current I_AC. A 5-mm-length MI element using a folded almost zero-magnetostrictive amorphous wire having a 120-μm diameter showed a sensitive rate of change of its inductance of more than 50% for an external low frequency field of about 10 Oe (800 A/m) applied in parallel with the element. The a-wire MI element works for a wire current having frequencies up to 1 MHz     

Finite dynamic element formulation for a plane triangular element

The higher order dynamic correction terms for the stiffness and inertia matrices associated with a triangular plane stress-strain finite dynamic element are developed in detail. Numerical results presented indicate that the adoption of these matrices along with a suitable quadratic matrix eigenproblem solver effects a significant economy in the free vibration solution of structures when compared with the analysis based on the usual finite element procedure. A FORTRAN IV computer program listing of the various relevant element matrices is also presented in the Appendix.     

New functionalities in abundant element oxides: ubiquitous element strategy

While most ceramics are composed of ubiquitous elements (the ten most abundant elements within the Earth''s crust), many advanced materials are based on rare elements. A ‘rare-element crisis’ is approaching owing to the imbalance between the limited supply of rare elements and the increasing demand. Therefore, we propose a ‘ubiquitous element strategy’ for materials research, which aims to apply abundant elements in a variety of innovative applications. Creation of innovative oxide materials and devices based on conventional ceramics is one specific challenge. This review describes the concept of ubiquitous element strategy and gives some highlights of our recent research on the synthesis of electronic, thermionic and structural materials using ubiquitous elements.     

An isoparametric joint/interface element for finite element analysis

A generally applicable and simple joint/interface element for three- and two-dimensional finite element analysis is presented. The proposed element can model joints/interfaces between solid finite elements and shell finite elements. The derivation of the joint element stiffness is presented and algorithms for the treatment of nonlinear joint behaviour discussed. The performance of the element is tested on typical problems involving shell-to-shell and shell-to-solid interfaces.     

New functionalities in abundant element oxides: ubiquitous element strategy

Abstract

While most ceramics are composed of ubiquitous elements (the ten most abundant elements within the Earth's crust), many advanced materials are based on rare elements. A ‘rare-element crisis’ is approaching owing to the imbalance between the limited supply of rare elements and the increasing demand. Therefore, we propose a ‘ubiquitous element strategy’ for materials research, which aims to apply abundant elements in a variety of innovative applications. Creation of innovative oxide materials and devices based on conventional ceramics is one specific challenge. This review describes the concept of ubiquitous element strategy and gives some highlights of our recent research on the synthesis of electronic, thermionic and structural materials using ubiquitous elements.     

Light element ceramics

An overview of a few structurally important light element ceramics is presented. Included in the overview are silicon nitride, sialon, aluminium nitride, boron nitride, boron carbide and silicon carbide. Methods of preparation, characterization and industrial applications of these ceramics are summarized. Mechanical properties, industrial production techniques and principal uses of these ceramics are emphasized. Contribution No. 76 from the Materials Research Laboratory     

Chemical element index

Chemical element index     

Global-local finite element

Finite element procedures usually require more degrees of freedom for a specified accuracy than does a classical Ritz procedure if suitable coordinate functions are available. This paper develops a combined global and local dependent variable representation which couples the conventional and finite element Ritz methods. This hybrid method preserves much of the flexibility of the finite element method while increasing the solution accuracy for a specified system order. The method is illustrated by examination of a beam and a plate vibration problem.     

Automatic element reordering for finite element analysis with frontal solution schemes

This paper describes an element reordering algorithm which is suitable for use with a frontal solution package. The procedure is shown to generate efficient element numberings for a wide variety of test examples. In an effort to obtain an optimum elimination order, the algorithm first renumbers the nodes, and then uses this result to resequence the elements. This intermediate step is necessary because of the nature of the frontal solution procedure, which assembles variables on an element-by-element basis but eliminates them node by node. To renumber the nodes, a modified version of the King¹ algorithm is used. In order to minimize the number of nodal numbering schemes that need to be considered, the starting nodes are selected automatically by using some concepts from graph theory. Once the optimum numbering sequence has been ascertained, the elements are then reordered in an ascending sequence of their lowest-numbered nodes. This ensures that the new elimination order is preserved as closely as possible. For meshes that are composed of a single type of high-order element, it is only necessary to consider the vertex nodes in the renumbering process. This follows from the fact that mesh numberings which are optimal for low-order elements are also optimal for high-order elements. Significant economies in the reordering strategy may thus be achieved. A computer implementation of the algorithm, written in FORTRAN IV, is given.