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1.
利用射频磁控共溅射方法,在Si衬底上制备了Ni88Cu12薄膜,并且研究了膜厚以及真空磁场热处理温度对畴结构和磁性的影响. X射线衍射结果表明热处理后的薄膜晶粒长大,扫描电子显微镜结果发现不同热处理温度下薄膜表现出不同的形貌特征.热处理前后的薄膜面内归一化磁滞回线结果显示,经过热处理的Ni88Cu12薄膜条纹畴形成的临界厚度降低,未热处理的Ni88Cu12薄膜在膜厚为210 nm时出现条纹畴结构,而经过300℃热处理的Ni88Cu12薄膜在膜厚为105 nm就出现了条纹畴结构.高频磁谱的结果表明,随着热处理温度的增加, Ni88Cu12薄膜的共振峰会有小范围的移动. 相似文献
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利用磁控溅射法制备了Nd28F66B6/Fe50Co50双层纳米复合磁性薄膜,研究了其结构和磁性.经873K退火处理15min后,利用x射线衍射仪测定薄膜晶体结构,采用俄歇电子能谱仪估算薄膜厚度和超导量子干涉仪测量其磁性.磁性测量表明,1)该系列薄膜具有垂直于膜面的磁各向异性.从起始磁化曲线和小回线的形状特征可知,矫顽力机制主要是由畴壁钉扎控制.2)对于固定厚度(10nm)层的硬磁相Nd-Fe-B和不同厚度(dFeCo=1-100nm)层软磁相FeCo双层纳米复合膜,剩磁随软磁相FeCo厚度的增加快速增加,而矫顽力则减少.当dFeCo=5nm时,最大磁能积达到160×103A/m.磁滞回线的单一硬磁相特征说明,硬磁相Nd-Fe-B层和软磁相FeCo层之间的相互作用使两相很好地耦合在一起.剩磁和磁能积的提高是由于两相磁性交换耦合所致. 相似文献
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磁性薄膜研究的现状和未来 总被引:14,自引:0,他引:14
概括介绍了近十几年来磁性薄膜研究的主要成果、应用和可能的发展情况,主要内容有:钙钛矿结构氧化物薄膜的磁性和庞磁电阻效应,磁性金属多层 膜的层间耦合和巨磁电阻效应及磁电阻磁头应用情况,光存储技术纳米点阵存储技术,磁电子学。 相似文献
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斯格明子(skyrmion)的概念最早是由英国的粒子物理学家Tony Skyrme提出,它被用来描述粒子的一个状态,是一种拓扑孤立子.磁性斯格明子是一种具有拓扑行为的新型磁结构,其空间尺寸为纳米量级,空间距离从纳米到微米量级可调;其存在温度涵盖从低温、室温到高温的宽温区;其材料体系不仅包括早期发现的低温区B20型中心对称破缺的铁磁体和螺旋磁有序的弱铁磁材料,也包括近期发现的室温及以上的中心对称六角结构磁性MnNiGa金属合金和磁性薄膜/多层膜体系.利用磁性斯格明子的拓扑磁结构可以实现类似于自旋阀或者磁性隧道结中的自旋转移矩效应,即外加电流可以驱动斯格明子,其临界电流密度比传统翻转磁性多层膜体系中磁矩的电流密度(一般为10~7A/cm~2)要低5个数量级,约为10~2A/cm~2,该临界值远低于硅基半导体技术中沟道电流密度的上限,在未来的磁信息技术中具有广泛的应用前景.本综述简单介绍了磁性斯格明子的发展历程,归纳总结了磁性斯格明子的材料体系,介绍了观察磁性斯格明子的实验手段,重点介绍了多场(磁场、电流、温度场)调控作用下中心对称MnNiGa合金和Pt/Co/Ta磁性多层膜体系中磁性斯格明子的产生、消失以及外场调控演变等动态行为. 相似文献
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采用交替沉积磁控溅射工艺制备了超薄多层的FeCoB SiO2 磁性纳米颗粒膜 .利用x射线衍射仪、扫描探针显微镜、透射电子显微镜分析了薄膜的微结构和形貌特征 .采用振动样品磁强计、四探针法、微波矢量分析仪及谐振腔法测量薄膜试样的磁电性能和微波复磁导率 .重点对SiO2 介质相含量、薄膜微结构对电磁性能产生重要影响的机理做了分析和探讨 .结果表明 :这类FeCoB SiO2 磁性纳米颗粒膜具有良好的软磁性能和高频电磁性能 ,2GHz时的磁导率 μ′高于 70 ,可以应用于高频微磁器件或微波吸收材料的设计 相似文献
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针对经过刻蚀的微细矩形磁性体系,将样品的形状及其磁晶易磁化轴的偏转两个因素引入经典的Stoner-Wohlfarth一致转动磁化模型中,发现磁性样品的微细化将使其特征星形线发生膨胀,而样品形状的缺陷及磁晶易磁化轴的偏转都将导致样品非对称特征星形线的产生.这些结果说明在诸如磁性随机存储器等基于微细磁性薄膜的工作中,薄膜形状及其磁晶易磁轴的角度不容忽略.
关键词:
磁性薄膜
Stoner-Wohlfarth模型
特征星形线
各向异性 相似文献
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利用Monte-Carlo方法和转移矩阵法研究了具有不同表面交换耦合Js和薄膜厚度 磁性多层 膜的表面和尺寸对磁相变的影响.模拟结果表明,系统的相变温度随薄膜层数的变化取决于Js/J(J为体内交换耦合),当Js/J大于某一临界值时,由于表面磁 有序先于体内磁有序 ,系统的相变温度随薄膜层数的增多而降低,反之,表面磁无序可与体内磁有序共存,系统 的相变温度随薄膜层数的增多而升高;当Js/J较小时,随Js增大 ,系统的居里温度缓慢 升高,趋近于体内相变温度,而当Js/J较大时,随Js增大,系统的 居里温度 呈线性升高.模拟结果与用转移矩阵法推导出的结果相当符合,且很好地解释了实验事实.
关键词:
磁星多层膜
交换耦合
Monte-Carlo模拟
转移矩阵法 相似文献
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采用交替沉积磁控溅射工艺制备了超薄多层的FeCoBSiO2磁性纳米颗粒膜.利用x射线衍射仪、扫描探针显微镜、透射电子显微镜分析了薄膜的微结构和形貌特征.采用振动样品磁强计、四探针法、微波矢量分析仪及谐振腔法测量薄膜试样的磁电性能和微波复磁导率.重点对SiO2介质相含量、薄膜微结构对电磁性能产生重要影响的机理做了分析和探讨.结果 表明:这类FeCoBSiO2磁性纳米颗粒膜具有良好的软磁性能和高频电磁性能,2GHz时的 磁导率μ′高于70,可以应用于高频微磁器件或微波吸收材料的设计.
关键词:
磁性纳米颗粒膜
高频特性
复磁导率
磁控溅射 相似文献
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具有条纹磁畴结构的磁性薄膜表现出面内转动磁各向异性,对于解决高频电子器件的方向性问题起着至关重要的作用.本文采用射频磁控溅射的方法,研究了NiFe薄膜的厚度、溅射功率密度、溅射气压等制备工艺参数对条纹磁畴结构、面内静态磁各向异性、面内转动磁各向异性、垂直磁各向异性的影响规律.研究发现,在功率密度15.6 W/cm~2与溅射气压2 mTorr(1 Torr=1.33322×102Pa)下生长的NiFe薄膜,表现出条纹磁畴的临界厚度在250 nm到300 nm之间.厚度为300 nm的薄膜比250 nm薄膜的垂直磁各向异性场增大近一倍,从而磁矩偏离膜面形成条纹磁畴结构,并表现出面内转动磁各向异性.高溅射功率密度可以降低薄膜出现条纹磁畴的临界厚度.在相同功率密度15.6 W/cm~2下生长300 nm的NiFe薄膜,随着溅射气压由2 mTorr增大到9 mTorr,NiFe薄膜的垂直磁各向异性场逐渐由1247.8 Oe(1 Oe=79.5775 A/m)增大到3248.0 Oe,面内转动磁各向异性场由72.5 Oe增大到141.9 Oe,条纹磁畴周期从0.53μm单调减小到0.24μm.NiFe薄膜的断面结构表明柱状晶的形成是表现出条纹磁畴结构的本质原因,高功率密度下低溅射气压有利于柱状晶结构的形成,表现出规整的条纹磁畴结构,高溅射气压会导致柱状晶纤细化,面内转动磁各向异性与面外垂直磁各向异性增强,条纹磁畴结构变得混乱. 相似文献
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J. Bai S. F. Fu S. Zhou X. Z. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):343-348
We investigate one magnetically nonlinear response of antiferromagnetic (AF) films to
incident electromagnetic waves, or the reflective optical bi-stability (ROB). Such
geometry is used, where the AF anisotropy axis and external static magnetic field both are
parallel to the film surfaces and normal to the incident plane. For TE incident waves with
the electric component transverse to the incident plane, the ROB of the AF film with the
absorption is calculated, but the case of TM incident waves is neglected since no magnetic
nonlinearity is induced in this geometry. The bi-stability is completely different in the
two resonant-frequency vicinities. Two kinds of bi-stability are found in the higher
vicinity, and their features versus incident power are opposite. We also find that there
are critical incident angle and critical film thickness for the existence of bi-stability.
The bi-stability disappears when the film thickness or incident angle exceeds its critical
value. Because the properties of bi-stable reflection sensitively depend on the external
field and the incident angle, this bi-stability can be easily modulated by means of
changing these quantities. 相似文献
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A.?Taroni B.?Hj?rvarsson 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(3):367-371
The properties of thin magnetic structures are influenced by many length scales that reflect both generic physics and chemical
detail. A striking example is the experimentally determined shift of the critical temperature as a function of film thickness.
While all systems experience a pronounced suppression in the transition temperature with decreasing film thickness, the magnitude
of this shift cannot be reconciled with established theoretical results. By means of detailed Monte Carlo simulations, we
address this discrepancy by investigating a model with long range interactions. The model also captures other features of
real thin magnets, such as an almost linear temperature dependence for the surface magnetization. Our results demonstrate
that the behavior of thin magnetic structures arises from a competition of length scales dictated by their slab-like geometry,
the presence of surface boundaries, and crucially, the range of the interactions present. 相似文献
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《Journal of magnetism and magnetic materials》1999,195(3):555-574
The phase diagram and the single-domain uniform state for a uniaxial ferromagnetic film with the superconducting layers covering one or both sides of a ferromagnet are investigated. The superconductor is supposed to be a second-order one and the interaction between the magnetic sub-system and with the conductivity electrons in a superconductor is purely electromagnetic and the vortices in a superconductor are pinned. The critical thickness of the magnetic film for which the uniform state becomes absolutely stable is calculated when the external magnetic field is supposed to be in-plane of the film. It is shown that the critical thickness of the film from the magnetic material with the quality factor Q>1 monotonically decreases as the magnetic field increases in the range from zero value to the value of the transition field where the collinear phase transforms into the angular (canted) phase. Further the critical thickness increases with the increase of the field. The quasi-single-domain magnetic film states were considered when the film thickness was close to the critical one. It is shown that for a thin isolated magnetic film the domain period exponentially increases with the decrease of the film thickness. Such dependence, however for the film with double-side superconducting cover and close to the transition into the single domain state becomes logarithmic and for the film covered by superconductor only on the one side varies as the power series. The single-domain state existence and the asymptotic behaviour of the domain structure is explained by the features of the asymptotic behaviour of the domain walls within the system. As for isolated magnetic film and for a film with the superconductor cover layers the transition from the collinear phase to the inhomogeneous state is the second-order phase transition and the transition from the uniform angular phase to the inhomogeneous phase is the first-order transition. 相似文献
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We study the critical behavior of magnetic thin films as a function of the film thickness. We use the ferromagnetic Ising model with the high-resolution multiple histogram Monte Carlo (MC) simulation. We show that though the 2D behavior remains dominant at small thicknesses, there is a systematic continuous deviation of the critical exponents from their 2D values. We explain these deviations using the concept of “effective” exponents suggested by Capehart and Fisher in a finite size analysis. The shift of the critical temperature with the film thickness obtained here by MC simulation is in an excellent agreement with their prediction. 相似文献
16.
The magnetic properties of a ferromagnetic thin film of face centered cubic (FCC) lattice with Heisenberg spin-S are examined using the high-temperature series expansions technique extrapolated with Padé approximations method. The critical reduced temperature of the system τc is studied as function of thickness of the film and the exchange interactions in the bulk, and within the surfaces Jb, Js and J⊥ respectively. A critical value of surface exchange interaction above which surface magnetism appears is obtained. The dependence of the reduced critical temperature on the film thickness L has been investigated. 相似文献
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Finite-temperature magnetic properties of iron thin films are investigated by computer simulation over a broad range of temperatures up to the point of the ferromagnetic–paramagnetic phase transition. The coupled dynamics of atoms and magnetic moments is treated using the large-scale spin–lattice dynamics (SLD) algorithm. We investigate surface and bulk magnetic properties of iron, and how these properties vary as a function of temperature, film thickness and surface crystallography. We find that magnetization at surfaces is enhanced at low temperatures and suppressed at higher temperatures, in agreement with experimental observations. The effective Curie temperature of a film decreases as a function of thickness. Short-range magnetic order and non-vanishing spin–spin spatial correlations are found above the Curie temperature. The spin autocorrelation functions exhibit slower oscillations with longer decoherence times near the surface. We also find that the directional spin disorder has a significant effect on the surface strain. 相似文献
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W. Gillijns F. Godts G.W. Ataklti A.V. Silhanek J. Van de Vondel J. Sautner B. Ilic V. Metlushko V.V. Moshchalkov 《Physica C: Superconductivity and its Applications》2010,470(19):880-882
The transport properties of an Al type-II superconducting thin film covering a Py plain film with a rectangular array of triangular holes are investigated. We show that, although the magnetization of the Py lies in the plane of the structure, both the critical temperature and the critical current are asymmetric with respect to the polarity of the external field, which is applied perpendicularly to the structure. The asymmetric nucleation can be explained in terms of field compensation effects between internal and external magnetic fields, whereas the presence of vortex–antivortex pairs are responsible for the observed features in the critical current. 相似文献
19.
F. Klose J. Thiele A. Schurian O. Schulte M. Steins O. Bremert W. Felsch 《Zeitschrift für Physik B Condensed Matter》1993,90(1):79-82
Multilayers of Ce and Fe show a low Curie temperature and saturation magnetization below a critical thickness of the individual Fe layers where amorphous growth occurs. We have studied on a series of such multilayers with different modulation lengths prepared by ion-beam sputtering the impact of hydrogen absorption on their magnetic properties. Hydrogenation was performed during film growth either reactively by introducing hydrogen gas into the UHV chamber or by irradiation with a beam of low-energy hydrogen ions. Hydrogen is absorbed only in the Ce layers, with a concentration near CeH2. For suitable modulation lengths, the Curie temperature and saturation magnetization are considerably enhanced with respect to the non-hydrided multilayers. This is correlated with the changes in structure and the quality of the interfaces induced by hydrogenation: the irradiation process itself reduces the critical thickness for amorphous growth of Fe, and the chemical interaction of hydrogen causes a considerable sharpening of the interfaces. 相似文献
20.
L. L. Afremov Yu. V. Kirienko A. A. Petrov 《Bulletin of the Russian Academy of Sciences: Physics》2014,78(2):104-107
The effect the thickness of an ultrathin film has on magnetic ordering is analyzed using the Ising model. It is shown that the dependence of the relative change in the Curie temperature on the thickness of an ultrathin film obeys a power law with an exponent equal to reverse critical exponent of spin-spin correlations ν = 0.69. The obtained results are in good agreement with the experimental data. 相似文献