共查询到20条相似文献,搜索用时 218 毫秒
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《中国新技术新产品》2021,(8)
由于交换耦合纳米复合多层膜体系同时拥有硬磁相的高矫顽力和软磁相的高剩磁的优点,因此引起了业界的广泛关注。该文运用微磁学方法,并采用计算机进行模拟,系统地研究了交换耦合SmCo_5/Co多层膜体系退磁中的磁化反转过程,得到了纳米复合多层膜体系的成核场。研究发现交换耦合SmCo_5/Co多层膜体系成核场H_N随硬磁相厚度L~h和软磁相厚度L~s变化而变化的规律,成核场随软磁相厚度的增大而减小,随硬磁相厚度的增大而增大;当软、硬磁相厚度同时增大时,成核场受到的影响会变小;当硬磁相厚度L~h5nm时,软磁相对成核场起主导作用而硬磁相对成核场的影响可以忽略不计。 相似文献
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TbFe/Fe交换耦合磁致伸缩多层膜的制备 总被引:4,自引:0,他引:4
采用双靶磁控溅射法制备了 TbFe/Fe交换耦合磁致伸缩多层膜,考察了热处理时间、Fe层厚度、溅射功率以及Ar气分压对多层膜低场磁致伸缩性能的影响。研究结果表明:TbFe 磁致伸缩层与软磁 Fe层之间通过交换耦合作用以及热处理能明显提高薄膜的软磁性能和磁致伸缩性能;TbFe/Fe多层膜的磁致伸缩性能对热处理时间、Fe 层厚度、溅射功率、Ar 气分压等薄膜沉积参数十分敏感;与 TbFe 磁致伸缩薄膜相比TbFe/Fe交换耦合磁致伸缩多层膜水平方向的矫顽力从 16kA/m降低到 9.6 kA/m。在外加磁场为8000 A/m条件下,TbFe/Fe磁致伸缩多层膜最大磁致伸缩系数可达1.58×10-4。 相似文献
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系统地研究了磁控溅射制备的Sm22Co78/Fe65Co35/Sm22Co78三层膜系统中,当软磁相的体积分数一定时,矫顽力和剩磁比随FeCo软磁层厚度(d)的变化,所有样品的磁滞回线均为单一硬磁相特征:说明FeCo软磁层与SmCo硬磁层之间的交换相互作用,使两相很好地复合在一起。当软磁相的体积分数为15%,20%,30%的情况下,矫顽力随d的变化都出现峰值,而剩磁比则单调增加,当体积分数为50%时,矫顽力随d的增加滑有峰值,但剩磁比还是单调增加,随着软磁体积分数的增加,矫顽力峰值及峰值位置都是单调减少。 相似文献
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退火温度对Nd2Fel4B/α—Fe磁性多层膜中相形成的影响 总被引:2,自引:0,他引:2
通过TEM和HRTEM对比研究了软磁层厚度为2.5nm的Nd2Fe14B/α—Fe型多层膜的显微结构.结果表明,在退火前的多层膜中Fe层为多晶,硬磁相以非晶的状态存在;在600℃以上退火后软磁层消失,生成的Nd2Fe14B型相被固定在硬磁层内;625℃退火后发现有Nd2Fe17相在硬磁层中析出,表明在多层膜退火过程中,退火温度对相转变的影响比退火时间的影响更大.Nd2Fe17相的析出可能是高温退火后磁性能下降的主要原因. 相似文献
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采用磁控溅射方法在SiO2基体上制备了FePt/FeMn/NiFe/Ta多层膜样品,通过FeMn/NiFe双层膜交换偏置的变化研究了硬磁FePt不同磁化状态对反铁磁层FeMn的影响。实验表明,磁化了的L10相FePt能使FeMn在较薄的情况下(4.5nm)对NiFe产生比较强的交换偏置;而未被磁化的FePt对FeMn/NiFe交换偏置影响并不明显。认为更薄的反铁磁层对另外的铁磁层产生交换偏置是由于硬磁与反铁磁的界面交换耦合作用能增强反铁磁的稳定性。 相似文献
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《真空科学与技术学报》2017,(8)
首先采用磁控溅射的方法在玻璃基片上沉积不同硬/软磁层厚度的FePt/Fe交换耦合双层膜,结合实验结果,依据微磁学理论对L10-FePt/Fe交换耦合双层膜的磁性能进行研究。结果显示,当FePt硬磁层厚度固定20nm,随Fe软磁层厚度的增加双层膜矫顽力逐渐减小。当Fe软磁层厚度超过其畴壁宽度时,其对矫顽力的影响大幅度降低。Fe软磁层厚度固定为10nm,FePt硬磁层厚度发生变化时,由于理论和实际双层膜界面的不同,导致对双层膜成核场起作用的临界硬磁层厚度也不一样。 相似文献
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The magnetic properties of nanocrystalline hard magnetic and soft magnetic are summarized. When the grain size becomes of the order f the magnetic exchange length exchange coupling occurs. The different concepts of exchange coupling in these materials are discussed. Exchange coupling leads in isotropic hard magnetic materials to a remanence enhancement. Soft magnetic materials exhibit due to exchange coupling a lower coercivity, lower losses and consequently also improved properties. 相似文献
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Chuanbing Rong Ying Zhang Narayan Poudyal Izabela Szlufarska Rainer J. Hebert M. J. Kramer J. Ping Liu 《Journal of Materials Science》2011,46(18):6065-6074
Fabrication of bulk nanocomposite materials, which contain a magnetically hard phase and a magnetically soft phase with desired
nanoscale morphology and composition distribution has proven to be challenging. Here we demonstrate that SmCo/Fe(Co) hard/soft
nanocomposite materials can be produced by distributing the soft magnetic α-Fe(Co) phase particles homogenously in a hard
magnetic SmCo phase matrix through a combination of high-energy ball milling and a warm compaction. Severe plastic deformation
during the ball milling results in nanoscaling of the soft phase with size reduction from micrometers to ~15 nm. Up to 35%
of the soft phase can be incorporated into the composites without coarsening. This process produces fully dense bulk isotropic
nanocomposite materials with remarkable energy-product enhancement (up to 300%) owing to effective inter-phase exchange coupling. 相似文献
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《Materials Science & Technology》2013,29(1):5-19
AbstractThe processing, structures and phase constitutions and the magnetic properties of nanocomposite hard magnetic alloys are reviewed. The emphasis is on rare earth (RE)–iron–boron alloys in which the hard magnetic phase RE2Fe14B is intermixed with one or more soft magnetic phases. Processing–structure–property relationships are the principal focus, in particular, the role of the hard and soft nanocrystallite dimensions in promoting intergrain ferromagnetic exchange coupling and the consequent enhancement of remanent magnetisation and the technologically important maximum energy density. The powder processing, chill block melt spinning, mechanical alloying and thin film deposition routes to develop nanocrystalline and nanocomposite structures are reviewed. The coercivity mechanism in ultrafine grained alloys and the influence of crystallite dimensions are discussed, as are the effects on intrinsic and extrinsic properties of RE substitutions, replacement of iron by other transition metals and enrichment of the boron content. Exchange enhancements in Sm–Co based nanocomposite bulk alloys and in nanoscale FePt/α-Fe composite thin films are briefly considered, together with thin film materials involving exchange coupling between ferromagnetic and antiferromagnetic phases, in core–shell type structures of transition metal compounds surrounded by oxides and in mechanically alloyed materials. The processing and magnetic properties of bonded magnets based on nanocrystalline/nanocomposite REFeB alloys are discussed. The possibility of producing anisotropic hard/soft composites with properties approaching the theoretical maximum is considered and the extent to which this goal has been realised for fully dense alloys identified. 相似文献
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Gutfleisch O Willard MA Brück E Chen CH Sankar SG Liu JP 《Advanced materials (Deerfield Beach, Fla.)》2011,23(7):821-842
A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifically, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure-property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy efficiency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed. 相似文献
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D Bahadur 《Bulletin of Materials Science》1992,15(5):431-439
Magnetic oxides, a major constituent of magnetic ceramic materials, are most extensively used in a variety of applications
as soft, moderate and hard ferrites. I review here its applications with special emphasis on some recent developments in magnetic
recording materials.
This work was partially supported by CSIR, New Delhi. 相似文献
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V. Raghavendra ReddyO. Crisan Ajay GuptaA. Banerjee V. Kuncser 《Thin solid films》2012,520(6):2184-2189
Structural and magnetic properties of exchange spring magnets consisting of hard magnetic (FePt) and soft magnetic (Fe and Co) bilayers, prepared by ion beam sputtering method are studied via X-ray diffraction (XRD), magneto-optic Kerr effect (MOKE) and vibrating sample magnetometry (VSM). Thin tracer layers of 57Fe were introduced in the soft layer in order to observe the Fe spin structure and interfacial diffusion by Conversion Electron Mössbauer Spectroscopy (CEMS). The observed in-plane exchange spring behavior extends also to the magnetic hard layer, whose switching field can be tuned in an unexpected manner via the top soft magnetic layer. To explain the observed phenomenon it is suggested that the increased switching field, found in the system with a Co/Fe bilayer acting as a single soft magnetic layer, is compatible with a peculiar behavior of the stiffness coefficient of the heterogeneous soft magnetic layer. According to this observation, possibilities to maximize the exchange spring effects via suitably chosen non-homogeneous soft magnetic layers are open. 相似文献
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McEnroe SA Carter-Stiglitz B Harrison RJ Robinson P Fabian K McCammon C 《Nature nanotechnology》2007,2(10):631-634
Magnetic exchange bias is a phenomenon whereby the hysteresis loop of a 'soft' magnetic phase is shifted by an amount H(E) along the applied field axis owing to its interaction with a 'hard' magnetic phase. Since the discovery of exchange bias fifty years ago, the development of a general theory has been hampered by the uncertain nature of the interfaces between the hard and soft phases, commonly between an antiferromagnetic phase and a ferro- or ferrimagnetic phase. Exchange bias continues to be the subject of investigation because of its technological applications and because it is now possible to manipulate magnetic materials at the nanoscale. Here we present the first documented example of exchange bias of significant magnitude (>1 T) in a natural mineral. We demonstrate that exchange bias in this system is due to the interaction between coherently intergrown magnetic phases formed through a natural process of phase separation during slow cooling over millions of years. Transmission electron microscopy studies show that these intergrowths have a known crystallographic orientation with a known crystallographic structure and that the interfaces are coherent. 相似文献
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It is proposed that permanent magnets can be made of composite materials consisting of two suitably dispersed ferromagnetic and mutually exchange-coupled phases, one of which is hard magnetic in order to provide a high coercive field, while the other may be soft magnetic, just providing a high saturation J/sub s/, and should envelop the hard phase regions in order to prevent their corrosion. A general theoretical treatment of such systems shows that one may expect, besides a high energy product (BH)/sub max/, a reversible demagnetization curve (exchange-spring) and, in certain cases, an unusually high isotropic remanence ratio B/sub r//J/sub s/, while the required volume fraction of the hard phase may be very low, on the order of 10%. The technological realization of such materials is shown to be based on the principle that all phases involved must emerge from a common metastable matrix phase in order to be crystallographically coherent and consequently magnetically exchange coupled.<> 相似文献
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Campanella H Jaafar M Llobet J Esteve J Vázquez M Asenjo A del Real RP Plaza JA 《Nanotechnology》2011,22(50):505301
We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials. 相似文献