硬磁/软磁交换弹簧多层膜的研究进展

交换弹簧现象在近几年是国际、国内的研究热点,取得了很大的进展,其中硬磁/软磁交换弹簧多层膜是很有价值的磁性材料.详细叙述了硬磁/软磁交换弹簧多层膜的理论和实验进展,着重讨论了硬磁/软磁交换弹簧多层膜的构造和原理,以及硬磁/软磁交换弹簧多层膜的用途,如巨磁致伸缩、永磁体、磁电阻等.     

Magnetic Structure Determinations at NBS/NIST

Magnetic neutron scattering plays a central role in determining and understanding the microscopic properties of a vast variety of magnetic systems, from the fundamental nature, symmetry, and dynamics of magnetically ordered materials to elucidating the magnetic characteristics essential in technological applications. From the early days of neutron scattering measurements at NBS/NIST, magnetic diffraction studies have been a central theme involving many universities, industrial and government labs from around the United States and worldwide. Such measurements have been used to determine the spatial arrangement and directions of the atomic magnetic moments, the atomic magnetization density of the individual atoms in the material, and the value of the ordered moments as a function of thermodynamic parameters such as temperature, pressure, and applied magnetic field. These types of measurements have been carried out on single crystals, powders, thin films, and artificially grown multilayers, and often the information collected can be obtained by no other experimental technique. This article presents, in an historical perspective, a few examples of work carried out at the NIST Center for Neutron Research (NCNR), and discusses the key role that the Center can expect to play in future magnetism research.     

Growth-Temperature Dependence of Magnetic and Magneto-Transport Properties of Epitaxially Grown MnAs/GaAs Hybrid Multilayers

We successfully fabricated epitaxial MnAs/GaAs multilayers with a total thickness of 300 nm using molecular beam epitaxy. The periodicity of the samples was fixed at 5 nm/5 nm and the growth-temperature dependence of the magnetic and magneto-transport properties were studied. All samples studied exhibited ferromagnetism above room temperature. The magnetic anisotropy and magnetoresistance are strongly dependent on the growth temperature. These results indicate that it is possible to manipulate the magnetic and magneto-transport properties by changing the growth temperature.     

Fe/V多层膜中亚稳结构Fe的形成及其磁学性能

采用电子束蒸镀的方法,通过改变多层膜的周期结构,成功地制备出具有不同晶格常数的bcc亚稳结构铁相的Fe/V多层膜,并研究了亚稳结构铁相形成对其磁性影响的规律.实验结果表明,多层膜中Fe与V层均由纳米晶粒组成.Fe层厚度小于2nm时,受多层膜界面自由能作用,Fe与V相互准外延生长,多层膜由点阵常数一致的体心立方相组成,其点阵常数随样品V/Fe层厚度比的增大而增加.多层膜平均原子磁矩随铁或钒层厚度的改变发生明显变化:当钒层厚度固定为6nm时,铁原子磁矩随铁层厚度的增加逐渐下降,在2nm处出现极小值后又随铁层增厚而回升;对于铁层厚度固定为1.6nm的样品,磁矩在钒层厚度为3nm时出现极大值.     

Multilayered materials: a palette for the materials artist

Developments in the understanding of how materials behave enable us to design material structures to display specified properties. We introduce multilayered materials as systems in which new properties, not found in their constituents in bulk form, can emerge. The importance of transmission electron microscopy to determine structure-property relationships in nanoscale multilayers through characterization of their atomic and electronic structure is emphasized. Two examples of technologically useful multilayer systems are considered in more detail: hard coatings made from nitride multilayer films and the new structures and magnetic properties that are found in some metal multilayer systems. Finally, we discuss the future developments that are required to fully exploit the novel properties found in multilayered materials.     

纳米磁性材料及其应用

纳米磁性材料是纳米材料中最早进入工业化生产,应用十分广泛的一类功能材料,纳米磁性材料的特性不同于常规的磁性材料,其原因在于与磁性相关联的特征物理长庆恰好处于纳米量级,例如,磁单畴尺寸,超顺磁性临界尺寸,交换作用长度,以主电子平均自由路磁程自由路程等大致处于1－100nm量级,当磁性体的尺寸与这些特征物理长度相当时,就会呈现反常的磁学与电学性质,利用这些新特性,已涌现出一系列新材料与众多应用。     

Microstructure, interdiffusion and magnetic properties of ZnO/MnOx multilayers grown by pulse laser deposition

ZnO/MnO_x nano-thin multilayers are fabricated by pulsed laser deposition with a sectioned target or “cake” technique. Structure and magnetic properties are measured, finding a magnetic signal that scales better with the number of interfaces than with the film volume, and an interlayer interdiffusion that happens at remarkably low film growth temperatures.     

块体纳米磁性材料研究进展

介绍了块体纳米磁性材料的形成机理以及制备方法与工艺,分别对软磁和永磁两体系中纳米磁性材料与传统磁性材料的磁性能进行了对比,并介绍了最新的几种纳米磁性材料体系。     

磁性材料在磁性纸中的应用

介绍了常用磁性材料及其制备方法,综述了细胞腔加填法和原位复合法制备磁性纤维和磁性纸的研究情况,进而对两种方法制备的磁性纸的印刷适应性进行分析。     

Influence of antiferromagnetic FeMn on magnetic properties of perpendicular magnetic thin films

We studied the influence of an anitferromagnetic FeMn layer on perpendicular magnetic anisotropy (PMA) and perpendicular coercivity (H_C⊥) of the CoCr/Pt multilayers and found that both PMA and H_C⊥ can be enhanced by the FeMn layer. We observed an obvious exchange coupling between FeMn and CoCr/Pt multilayers which enhances PMA and may increase the density of pinning sites that can pin the domain wall of ferromagnetic layers and lifts up energy barrier during the propagation of domain walls. This leads to the enhancement of H_C⊥. Moreover, X-ray diffraction results shows that the (111) texture of the FeMn layer enhances that of the CoCr/Pt multilayers, leading to the increase of PMA and H_C⊥ as well. This result is of great significance on improving magnetic properties of perpendicular magnetic recording media by using an antiferromagnetic manganese alloy.     

金属磁粉心的研究现状及发展趋势

金属磁粉心材料由金属软磁粉末、有机或无机绝缘添加剂和粘结剂组成,其是以金属软磁粉末为原料,经过绝缘包覆、压制成型和热处理等工艺制成的软磁复合材料。本文系统阐述了金属磁粉心材料的材料分类、制备工艺、磁性能及其应用,同时对其未来的发展趋势做了预测,为今后金属磁粉心的研究与发展提供了参考。     

New thin film permanent magnets

Abstract

An overview is provided of research on coupled hardsoft magnetic multilayers as model exchange-spring systems, with an emphasis on uncovering the fundamental magnetic reversal processes and the correlation between microstructure and magnetic properties. The goal is to illustrate the rich opportunities to understand and hopefully improve permanent magnets by utilising the principles of nanotechnology and the microscopic tools of the modern materials science.     

TbDyFe/FeNi多层膜的磁致伸缩性能

本文采用磁控溅射工艺制备了TbDyFe/FeNi多层膜,研究了TbDyFe/FeNi多层膜的磁致伸缩性能及其影响因素.研究表明,随着FeNi膜层以及TbDyFe膜层厚度的减少,多层膜磁致伸缩性能增强,线性变化能力增强;通过真空退火、外加磁场镀膜和外加应力镀膜能够有效地提高TbDyFe/FeNi多层膜的磁致伸缩性能.     

有机磁性结构型化合物的研究进展

有机磁性材料因其具有质轻、结构多样性、易用化学方法合成、并且还可以通过引入特定的官能团而产生新功能等特性，在超高频装置、高密度存贮材料、吸波材料、微电子工业和宇航等领域具有广阔的应用前景。介绍了磁性的本质与来源，分别从纯有机磁性化合物和金属有机磁性化合物两方面对结构型磁性化合物进行综述，重点阐述金属有机磁性化合物中的桥联型、二茂金属类、席夫碱型以及含双噻唑环类磁性化合物的发展及其性能研究，并提出了结构型磁性化合物的理论与应用研究方向。     

磁性多孔碳材料的研究进展

磁性多孔碳材料同时具有磁性和多孔性质,其拥有丰富的孔道结构、高的比表面积、高孔容、良好的活性位点和磁性可分离等优异的性能,可以很好的解决多孔碳材料在应用过程中难分离回收等问题,因此,磁性多孔碳材料已经在吸附领域得到广泛的应用。按照孔径大小、磁性强弱以及组合方式的不同将磁性多孔碳材料进行了分类,并综述了近年来磁性多孔碳材料的制备方法以及吸附应用,最后,对磁性多孔碳材料的应用前景进行了展望。     

NiO／NiFeCo／Cu／NiFeCo自旋阀结构的巨磁电阻效应及影响因素的研究

用电子蒸发的方法制备ＮｉＯ／ＮｉＦｅＣ／Ｃｕ／ＮｉＦｅＣｏ自旋阀多层膜,通过磁场中退火得到好的偏置型自旋阀ＧＭＲ效应。通过对制备态以及磁场退火后样品的ＭＲ曲线的研究,讨论了交换耦合作用,单层磁性能以及层间耦合作用对材料ＧＭＲ效应的大小和磁场灵敏度的影响,得出提高交换耦合作用,改善单层磁性能和尽可能减小层间耦合将有得于得到高性能的偏置型自旋阀ＧＭＲ材料的结论。     

Nd_2Fe_(14)B/α-Fe交换耦合双层薄膜磁性能

利用微磁学理论模拟计算了Nd2Fe14B/α-Fe交换耦合双层膜的磁滞回线,并对双层膜体系的剩磁、矫顽力、最大磁能积与软磁层厚度的关系进行了研究。结果显示,软磁层厚度小于临近尺寸时,磁滞回线为矩形,双层膜完全耦合;软磁层厚度与磁性能的关系表明,随着软磁层厚度的增加,剩磁和最大磁能积先增大后减小,而矫顽力单调下降。     

磁性多层膜系统自旋重取向行为的Monte Carlo模拟

依据Heisenberg模型,利用Monte　Carlo方法模拟了磁性多层膜系统的自旋重取向行为,研究了各向异性、偶极相互作用以及外磁场对系统自旋取向的影响。通过模拟计算,获得了系统组态、磁分量等随偶极相互作用、外加磁场和温度的变化规律,重点研究了磁性多层膜系统在外磁场作用下的磁滞现象。     

Effect of various single metallic seed-layers on the magnetic properties of Co/Pd multilayers

We studied the effects of Pd, Ru, and Ta seed-layers on the perpendicular magnetic properties of Co/Pd multilayers, promising materials for high-density magnetic recording media. Among the various seeds, the Ta seed-layer demonstrated a large coercivity and most highly promoted fcc (111) preferred orientation of the Co/Pd multilayer. We also patterned films into island arrays with sizes of 2 × 2 μm², 5 × 5 μm², and 10 × 10 μm² to investigate the effect of size on the magnetic properties. The coercivity increased as the island size decreased. The 2 × 2 μm² patterned Co/Pd multilayer with the Ta seed-layer showed a coercivity about six times greater than that of the un-patterned film. This increase can be explained by a change in the magnetization reversal mechanism from domain wall propagation to domain rotation.     

长链共轭席夫碱吸波材料的研究进展

阐述了长链共轭席夫碱吸波材料的吸波机理,综述了席夫碱吸波材料的电性能、磁性能、吸波性能的研究现状,展望了该类吸波材料的电性能、磁性能以及吸波性能的改善研究情况,可通过设计合成长链共轭结构的席夫碱、引进手性螺旋结构、利用过渡金属或稀土金属配位这3个方面来提高席夫碱吸波材料的电性能、磁性能以及吸波性能。