共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
利用交流电化学沉积方法在氧化铝模板中制备了一维结构的FexCo1-x(0 ≤ x ≤ 0.51)二元合金纳米线阵列.X射线衍射结果显示,单质Co纳米线为(100)择优取向的hcp结构,FeCo合金纳米线则呈现(110)择优取向的bcc结构,而且衍射峰随纳米线中Fe含量的增加向低角度偏移.室温磁性测量结果显示, FeCo合金纳米线具有较好的磁特性.与Co纳米线相比,Fe的引入改善了Co纳米线的磁性能,使其呈现出较大的矫顽力和较高的矩形比.采用一致转动模型和对称扇形机理的球链模型分别计算了FeCo合金纳米线的矫顽力, 发现其磁化反转机理与对称扇形机理的球链模型相符合. 相似文献
3.
4.
5.
利用直流电化学沉积法,在多孔阳极氧化铝模板中首次制备出了具有[220]取向的单晶面心立方结构的CoCu固溶体合金纳米线阵列,其Co含量高达70%.透射电子显微镜显示纳米线均匀连续,具有较高的长径比,约为300.磁性测量表明所制备的Co(70)Cu(30)合金纳米线具有超高的矫顽力Hc//=2438 Oe(1 Oe=79.5775 A/m)和较高的矩形比S//=0.76,远高于以往报道的CoCu合金纳米线的磁性,分析表明磁性好的主要原因是由于较高Co含量和高形状各向异性.通过磁性测量和模型计算,得到Co(70)Cu(30)合金纳米线阵列在反磁化过程中遵从对称扇型转动的球链模型,并从结构的角度分析了Co(70)Cu(30)合金纳米线阵列的反磁化行为. 相似文献
6.
在氧化铝模板的纳米孔洞中, 用电化学的方法沉积铁镍合金纳米线,经过550℃30h氧化处理 , 成功制备出 NiFe2O4纳米线阵列. 分别用扫描电子显微镜 (SEM) 、透射电 子显微镜 (TEM) 、x射线衍射仪 (XRD) 和振动样品磁场计 (VSM) 对样品的形貌、晶体结构 和磁学性质进行了表征测试. SEM和TEM观察结果显示氧化铝模板的孔洞分布均匀,孔心距约 为110nm; 纳米线的直径约为70nm. XRD显示纳米线阵列的物相结构为NiFe2O4; VSM测试结果表明,NiFe2O4纳米线阵列膜的易磁化方向垂直于膜面. 当垂直 磁化时磁滞回线的矩形比约为05,矫顽力为41×103A/m,比氧化处理前的铁镍合金 纳米线阵列都有显著提高.
关键词:
纳米线
Ni Fe2O4
矫顽力 相似文献
7.
利用直流电化学沉积法, 在多孔阳极氧化铝模板中首次制备出了具有[220]取向的单晶 面心立方结构的CoCu固溶体合金纳米线阵列, 其Co含量高达70%.透射电子显微镜显示纳米线均匀连续, 具有较高的长径比, 约为300. 磁性测量表明所制备的Co70Cu30 合金纳米线具有超高的矫顽力Hc//=2438 Oe(1 Oe=79.5775 A/m)和较高的矩形比S//=0.76, 远高于以往报道的CoCu合金纳米线的磁性, 分析表明磁性好的主要原因是由于较高Co含量和高形状各向异性. 通过磁性测量和模型计算, 得到Co70Cu30 合金纳米线阵列在反磁化过程中遵从对称扇型转动的球链模型, 并从结构的角度分析了Co70Cu30合金纳米线阵列的反磁化行为. 相似文献
8.
研究了纳米Nd2Fe14B/α-Fe复合永磁材料中晶粒交换耦合相互作用对有效各向异性的影响和变化规律.结果表明:晶粒之间的交换耦合作用使材料的有效各向异性Keff随晶粒尺寸的减小而下降、随软磁性相成分的增加而降低. 当晶粒尺寸 减小到4nm时,Keff值减小为其各自通常各向异性常数值的1/3—1/4.有效各向异性的变化特点与矫顽力的变化规律基本相同.纳米复合永磁材料矫顽力的降低主要由于有效各向异性的减小而引起.
关键词:
纳米复合永磁材料
交换耦合相互作用
有效各向异性
矫顽力 相似文献
9.
10.
利用直流电沉积法在多孔阳极氧化铝模板中制备出了一系列Fe100-xPdx磁性纳米线阵列. Pd的增加使纳米线的总体磁性降低,各向异性和矫顽力也发生了较大的变化. 当Pd含量高达x=30时,纳米线仍有相当高的矫顽力(7.48 kA/m)和较明显的各向异性,但当Pd的含量增加到50%时,纳米线的易磁化方向由平行线的方向反转到垂直线的方向. 实验证明,这是由于在Fe80Pd20和Fe70Pd30中连续的磁性相在Fe50Pd50纳米线中变成了与非磁性相相互间隔的非连续片状结构. 片状磁性相的形状各向异性使易磁化方向转变到垂直纳米线轴的方向. 从生长动力学的角度对Fe50Pd50纳米线中这种片状的形成进行了解释.
关键词:
纳米线
电化学沉积
磁性 相似文献
11.
本文采用溶胶-凝胶工艺并结合脉冲激光沉积技术, 在Pt/Ti/SiO2/Si衬底上制备了Co/Co3O4/PZT多铁复合薄膜. 对复合薄膜的微结构和组分进行了表征, 并系统研究了复合薄膜中的交换偏置效应及其对磁电耦合作用的影响. 研究结果表明, 复合薄膜在77 K具有明显的交换偏置效应, 交换偏置场达到80 Oe, 且交换偏置场及矫顽场均随温度降低而增大. 当温度降低到10 K时, 交换偏置场增至160 Oe. X射线光电子能谱(XPS)测试结果证实在Co和Co3O4界面处存在约5 nm厚的CoO层, 表明77 K下的交换偏置效应源自反铁磁的CoO层对Co的钉扎作用. 观察到复合薄膜的电容-温度曲线随着外加磁场大小和方向的改变而呈现出规律性的变化, 表明复合薄膜存在磁电耦合效应. 进一步研究发现, 在低温下复合薄膜呈现出各向异性的磁电容效应, 与磁场大小和方向密切相关. 复合薄膜的这种磁电耦合特性主要与复合体系的交换偏置效应及基于界面应力传递的磁电耦合作用有关, 本文对其中的物理机理进行了详细讨论与分析. 相似文献
12.
Investigation of L1_0 FePt-based soft/hard composite bit-patterned media by micromagnetic simulation 下载免费PDF全文
《中国物理 B》2015,(6)
The soft/hard composite patterned media have potential to be the next generation of magnetic recording,but the composing modes of soft and hard materials have not been investigated systematically.L10 Fe Pt-based soft/hard composite patterned media with an anisotropic constant distribution are studied by micromagnetic simulation.Square arrays and hexagonal arrays with various pitch sizes are simulated for two composing types:the soft layer that encloses the hard dots and the soft layer that covers the whole surface.It is found that the soft material can reduce the switching fields of bits effectively for all models.Compared with the first type,the second type of models possess low switching fields,narrow switching field distributions,and high gain factors due to the introduction of inter-bit exchange coupling.Furthermore,the readout waveforms of the second type are not deteriorated by the inter-bit soft layers.Since the recording density of hexagonal arrays are higher than that of square arrays with the same center-to-center distances,the readout waveforms of hexagonal arrays are a little worse,although other simulation results are similar for these two arrays. 相似文献
13.
A simple process for fabricating submicrometric magnetic arrays employing interference lithography, sputtering deposition and lift-off processes is proposed and demonstrated. The magnetic properties of cobalt (Co) arrays were measured and compared with those of a continuous Co magnetic film. The results show a dependence of the hysteresis curve on the orientation of the field as regards the array, which is correlated with the anisotropy of the structures and a dependence of the coercive field on the periodicity of the arrays. Moreover, an exchange bias effect was observed, which is ascribed to a ferromagnetic/antiferromagnetic (FM/AFM) coupling between Co and a thin surface cobalt oxide (CoO) layer. 相似文献
14.
15.
Imaging or beam-steering systems employing a periodic array of microlenses or micromirrors suffer from diffraction problems resulting from the destructive interference of the beam segments produced by the array. Simple formulas are derived for beam steering with segmented apertures that do not suffer from diffraction problems because of the introduction of a moving linear phase shifter such as a prescan lens before the periodic structure. The technique substantially increases the resolution of imaging systems that employ microlens arrays or micromirror arrays. Theoretical, numerical, and experimental results demonstrating the high-resolution imaging concept using microlens arrays are presented. 相似文献
16.
Exchange-spring TbFeCo/YFeCo multilayers exhibit interesting magnetic and magnetostrictive properties that are rather promising
for application in microsystems. In this paper, we present a study of the effect of the exchange coupling on the magnetic
properties of these magnetostrictive multilayers. An exchange bias phenomenon, revealed by a shift of the minor hysteresis
loop along the applied field axis, is found as the result of the creation of interfacial domain walls. This effect strongly
depends on the magnetic properties of the soft YFeCo layer, and becomes more pronounced at low temperatures due to the enhancement
of the magnitude of the exchange coupling between the layers. 相似文献
17.
We investigate the structure and exchange coupling in TbFeCo/FePt bilayer films. It is found that FePt has the L10 structure and the easy axis of the FePt film is perpendicular to the film plane. Results of the vibrating sample magnetometer and the magneto-optical Kerr effect measurements show a strong perpendicular exchange coupling between the ferrimagnetic TbFeCo layer and the hard ferromagnetic FePt layer. The magnetization direction of each layer and the process of magnetization reversal are discussed in detail. The switching field dependence on the exchange coupling has been modelled by micromagnetic simulation and the interlayer coupling constant is about -0.9 erg/cm^2 according to this simulation. 相似文献
18.
本文采用气相团簇束流沉积法制备了不同铁铬比的铁铬合金密集团簇点阵,研究了团簇点阵中复杂的多相结构和各种耦合效应.当合金中铬含量较大时,在团簇中能够观测到一种晶格失配的类四方结构,这种结构的出现导致了不同铁铬比的合金团簇中交换偏置效应的不同.随着铬的含量增加,合金团簇的交换偏置场减小,而团簇间的偶极相互作用增强.在合金团簇的铁磁-超顺磁转变温度以上,能明显观察到在类四方结构团簇中有更大的残存矫顽力与剩磁.在场冷条件下,对矫顽力和偏置场随温度变化的研究表明含有更多类四方结构的合金团簇有更好的热稳定性和更大的各向异性. 相似文献
19.
Li J 《Physical review letters》2003,90(21):217601
In this Letter, we discuss the dramatically enhanced electrostriction and dielectric constant in an all-organic composite consisting of polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] copolymer matrix and copper-phthalocyanine (CuPc) particles, which could not be explained by traditional composite theory. Using a Landau-type potential energy combined with energy minimization, we demonstrate that the dramatic property enhancement is due to the exchange coupling between the dielectrically hard P(VDF-TrFE) and dielectrically soft CuPc, which becomes dominant when the heterogeneity size of the composite is comparable to the exchange length. The exchange coupling is a very effective mechanism for the enhancement of functional properties in ferroelectric and dielectric systems, and its variation with various material parameters is demonstrated and discussed. 相似文献
20.
Yong-Goo Yoo Seong-Cho Yu P.D. Kim B.A. Belyaev A.M. Mahlaev D.L. Khalyapin 《Journal of magnetism and magnetic materials》2006
The exchange coupling strength of NiFe/Cu/IrMn trilayer films was examined with both a new magneto optical Kerr effect (MOKE) method developed for the exchange coupling field determination and ferromagnetic resonance (FMR) measurements. We found that the value for exchange coupling field obtained by the MOKE technique coincided with FMR result with high accuracy. Other peculiarities of FMR measurements due to interlayer exchange coupling such as angular dependence of resonance field on Cu spacer thickness are also shown in the article. 相似文献