IrMn顶钉扎自旋阀中Ta缓冲层的优化研究

通过直流磁控溅射法在硅 /二氧化硅基底上沉积了Ta膜 ,Ta/NiFe双层膜和IrMn顶钉扎自旋阀薄膜 ,研究了Ta、Ta/NiFe膜的晶格结构和表面情况 ,及自旋阀的磁性能 ,结果表明 ,自旋阀的磁电阻率、矫顽力和交换场等性能与Ta缓冲层厚度有密切的关系 ,在Ta缓冲层为 3nm时自旋阀的磁电阻率 (9 2 4 % )和交换场 (2 5 5× (10 3 / 4π)A/m)达到最大值 ,而矫顽力 (2 4 3× (10 3 / 4π)A/m)比较小     

IrMn基自旋阀结构多层膜的热弛豫研究

采用磁控溅射方法制备结构为CoFe/Cu/CoFe/IrMn的自旋阀结构多层膜,研究它的热弛豫现象.实验表明,多层膜在其负饱和场中等待时,钉扎层的磁滞回线向正场方向移动,交换偏置场单调减小,并且随温度升高而加速减小.交换偏置场的减小是由反铁磁层的反转引起的,它可以看作是反铁磁磁矩越过一定能垒的热激活反转过程.温度升高后,能垒的分布发生了改变.     

Cu/X(X=Cr,Nb)纳米多层膜力/电学性能的尺度依赖性

利用纳米压痕实验以及四探针法,系统研究了相同层厚Cu/X(X=Cr,Nb)纳米金属多层膜的力学性能(强/硬度)和电学性能(电阻率)的尺度依赖性.微观分析表明:Cu/X多层膜调制结构清晰,Cu层沿{111}面择优生长,X层沿{110}面择优生长.纳米压入结果表明,Cu/X多层膜的强度依赖于调制周期,并随调制周期的减小而增加.多层膜变形机制在临界调制周期(λ~c≈25 nm)由Cu层内单根位错滑移转变为位错切割界面.多层膜的电阻率不仅与表面/界面以及晶界散射相关,而且在小尺度下受界面条件显著影响.通过修正的FS-MS模型可以量化界面效应对多层膜电阻率的影响.Cu/X纳米多层膜可以通过调控微观结构实现强度-电导率的合理匹配.     

Cu/Ni和Cu/Nb纳米多层膜的应变率敏感性

为研究调制周期和界面结构对纳米多层膜应变率敏感性的影响,采用电子束蒸发镀膜技术在Si基片上制备了不同周期(Λ=4 nm,12 nm,20 nm)的Cu/Ni纳米多层膜,采用磁控溅射技术在Si基片上制备了不同周期(Λ=5 nm,10 nm,20 nm)的Cu/Nb纳米多层膜。在真空条件下,对Cu/Ni纳米多层膜进行了温度分别为200和400℃、时间4 h的退火处理,对Cu/Nb纳米多层膜进行了温度分别为200、400和600℃,时间为4 h的退火处理。采用XRD和TEM表征了Cu/Ni和Cu/Nb纳米多层膜的结构,采用纳米压痕仪获取了不同加载应变率(0.005、0.01、0.05和0.2 s~(-1))下纳米多层膜的硬度。结果表明,应变率敏感性受到界面结构和晶粒尺寸的影响,非共格界面密度提高以及晶粒尺寸变大均可导致应变率敏感性下降。当周期变大时,Cu/Ni纳米多层膜的非共格界面密度提高,晶粒尺寸变大,应变率敏感性指数m减小;当周期变大时,Cu/Nb纳米多层膜的非共格界面密度下降,晶粒尺寸变大,m基本不变。随退火温度上升,Cu/Ni和Cu/Nb纳米多层膜应变率敏感性大体上呈现下降趋势,这是由退火过程中非共格界面密度上升和晶粒长大共同引起的。     

Co/Cu/Co纳米多层膜的铁磁耦合效应

采用洛仑兹电子显微镜研究了磁控溅射沉积制备的Cu(20 nm)/Co/Cu/Co纳米多层膜磁畴结构随铁磁层间耦合效应的变化. Cu中间层厚度较薄时, 由于铁磁层之间的耦合作用, 纳米多层膜为垂直易磁化, 磁畴为磁泡结构, 磁泡的平均直径随Cu中间层厚度的增加而减小, 多层膜矫顽力呈减小趋势. 当Cu中间层厚度大于3 nm时, 铁磁层之间的耦合作用减弱, 纳米多层膜为面内易磁化, 磁泡结构的磁畴消失, 全部为具有波纹状的接近180°畴壁的磁畴结构.     

Ni /Ti 多层膜界面状态优化分析

目的减小Ni/Ti多层膜表面粗糙度,提高Ni/Ti多层膜对中子束的反射率。方法采用离子束辅助沉积设备沉积Ni/Ti周期性多层膜,通过不同抛光时间和不同离子能量轰击对多层膜界面进行清洗抛光;采用反应溅射法,在镀Ti层时使用氢气和氩气混合气为工作气体,将H原子掺入Ti层以改变晶粒结构而影响多层膜界面状态。结果随着辅助离子源功率的增加,Ni/Ti多层膜的表面粗糙度增加;在合适的离子能量下,随着抛光时间的不断增加,Ni/Ti多层膜的表面粗糙度逐渐减小。Ti层中掺H的Ni/Ti多层膜比未掺H的多层膜表面粗糙度小,界面更加清晰。结论低能量的离子轰击条件下,适当的抛光时间能对多层膜实现较好的抛光效果。Ti层中掺入H原子,抑制了Ni原子与Ti原子的扩散,减小了Ti膜层晶粒大小,从而抑制了表面粗糙度的增加。     

铜互连多层膜系中自对准CuSiN层的微结构及其热稳定性

通过等离子体与Cu膜表面的分步反应合成了厚约4 nm的CuSiN自对准层.采用高分辨透射电子显微术(HRTEM)、纳米电子束探针能谱(EDS)和X射线衍射(XRD)表征CuSiN和Si/SiO2/TaN/Ta/Cu(CuSiN)/SiC:H/SiOC:H多层膜基体系的微结构和热稳定性.表明CuSiN层两侧分别出现SiN和Cu(Si)层,显著提高Cu/SiC:H/SiOC:H结构的热稳定性,其机制是在500℃退火温度条件下CuSiN层仍能够稳定存在,从而阻碍了Cu原子向SiC:H/SiOC:H介质薄膜体内的扩散.     

不同退火温度下Cu/Ni纳米多层膜的结构与力学性能稳定性

为研究不同退火温度下Cu/Ni纳米多层膜的结构与力学性能稳定性,采用电子束蒸发镀膜技术在Si(100)基片上沉积不同周期(Λ为4,12,20 nm)的Cu/Ni多层膜,在真空条件下对试样进行温度为200℃和400℃,时间为4 h的退火处理,分析了沉积态(未退火态)与退火态Cu/Ni多层膜纳米压痕硬度、弹性模量与微结构的演变,讨论了不同调制周期Cu/Ni多层膜的热稳定性。结果表明:200℃下4 h退火后,Λ为4,12和20 nm的Cu/Ni多层膜均保持了硬度与弹性模量的热稳定性。而在400℃下4 h退火后,Λ为12 nm的Cu/Ni多层膜出现了硬度和弹性模量的软化现象,硬度由6.21 GPa降低至5.83 GPa,弹性模量由190 GPa降低至182 GPa。这是由于共格界面被破坏,界面共格应力对Cu/Ni多层膜力学性能贡献作用削弱导致的。     

NiFeSiMnMo/Cu/NiFeSiMnMo多层膜中Cu层对巨磁阻抗效应的影响

在康宁玻璃上用真空蒸镀法沉积NiFeSiMnMo单层膜、NiFeSiMnMo/Cu双层膜和NiFeSiMnMo/Cu/Ni-FeSiMnMo多层膜.对单层膜和双层膜的软磁性能进行了分析,对多层膜的巨磁阻抗效应随Cu层宽度的变化进行了研究.实验研究表明,NiFeSiMoMn/Cu双层膜比NiFeSiMnMo单层膜矫顽力小、饱和磁化强度高;多层膜Ni-FeSiMnMo/Cu/NiFeSiMnMo随着Cu层宽度的增加巨磁阻抗比上升到一个最大值后下降,在磁性层宽度3mm的情况下,Cu层宽度在0.7mm时,巨磁阻抗比最大.     

非对称界面耦合对LaCoO_3/LaMnO_3双层膜性能调控研究（英文）

通过高分子辅助溶胶凝胶自旋涂沉积法在(100)取向的SrTiO_3衬底上制备出LaCoO_3/LaMnO_3双层膜。在LaMnO_3表面生长一层LaCoO_3膜后,由于二者结构对称性差异,最终会在膜层界面处形成非对称界面耦合。由于非对称耦合作用,双层膜的铁磁转变温度从单层LaMnO_3的262 K下降为200 K。此外,由于界面处Mn-O-Co的双交换作用,与单层LaMnO_3薄膜的矫顽场相比,双层膜的矫顽场增大了约500%。研究结果表明,不同结构和性质的薄膜重组为多层膜的基础研究和高性能功能材料的应用提供了一种新的结构设计途径。     

INFLUENCE OF THE NONMAGNETIC METAL SPACER ON THE MAGNETIC PROPERTIES AND MICROSTRUCTURE OF THE MULTILAYER FILMS

Ta / NiFe/Bi （ Ag, Cu ）/FeMn/Ta and Ta / NiFe1/FeMn / Bi （ Ag, Cu ）/NiFen/Ta films were prepared by magnetic sputtering. The texture and the dependences of the exchange-coupling field on the thickness of Bi, Ag, and Cu in Ta/NiFe/Bi（Ag, Cu） /FeMn/Ta and Ta/NiFe/FeMn/Bi（Ag, Cu）/NiFe/Ta films were studied. XPS results indicate that the Bi atoms migrated into the FeMn layer during the deposition process and a FeMnBi alloy was probably formed or the Bi atoms existed as an impurity in the FeMn layer in Ta/NiFe/Bi（Ag, Cu ）/FeMn/Ta. Otherwise, in Ta/NiFe/FeMn/Bi （Ag, Cu）/NiFe/Ta films, Bi, Ag, and Cu atoms do not remain entirely at the interface of the FeMn/ NiFeⅡfilm, but at least partly segregate to the surface of the NiFe film.     

STUDY OF THE EXCHANGE BIAS FIELD OF NiFe/FeMn BILAYERS

1. IntroductionIll recellt }'ears, there ha\-e been extellsit-e il1terests ill the exchal1ge al1isotroP},, wl1ichttas first discoveretl b}' NIeiklejol1n aud Beal,[1l more thall fOrt} }-ears ago. F1ndan1el1tally,excllallge allisotrop}' is all illterfacial …     

INTERFACE REACTION IN MAGNETIC MULTILAYERS

1. Introduction"Exchange bias" [1], which refers to a shift (He. ) in the magnetization curve away fromthe zero field axis is an important phenomenon observed when a ferromagnet (FM) is incontact with an antiferromagnet (AF). Despite four decades of researcIl since its discovery,an understanding of this effect has still not been established. In recent years, the exchangecoupling between ferromagnetic (FM) and antiferromagnetic (AF) thin filIns has receivedincreasing attention in physics be…     

Giant magnetoresistance and super-paramagnetism in electrodeposited NiFe/Cu multilayers

The giant magnetoresistance of electrodeposited NiFe/Cu multilayers from a single bath under potentiostatic control is studied. The observed nonsaturating behavior urged us to investigate the probability of the occurrence of superparamagnetic regions in these multilayers. In this research, for the first time, the presence of super-paramagnetic regions in electrodeposited NiFe/Cu multilayers is shown and proved via high resolution transmission electron microscopy. The reason was found to be the existence of a very large anodic transient at the beginning of the copper deposition pulse, which could be eliminated by choosing a more negative potential.     

Spin-valve magnetoresistance in Co/Si/（Co/Cu/Co） multilayers

A series of Co/Si/（Co/Cu/Co） multilayers and Co/Si/Co sandwiches were prepared by high vacuum electron-beam evaporation. It was found that a Si spacer （≥0.9 nm） could greatly decrease the interlayer coupling in Co/Si/Co sandwiches and there was no magnetoresistance（MR） or spin-valve MR in them due to the high resistivity of Si spacer. While in Co/Si/（Co/Cu/Co） multilayers, we observed a spin-valve MR of about 0.5% through a nominal 2.7 nm Si spacer at room temperature. The spin-valve MR in Co/Si/（Co/Cu/Co） multilayers was attributed to the enhanced spin polarization of conduction electrons caused by the top Co/Cu/Co sandwich with GMR mechanism and high spin-dependent scattering at Co/Cu interface.     

Spin Valves with the Controlled Shift of Low-Field Hysteresis Loop and High-Sensitive Sensing Elements on Their Basis

Metallic multilayer spin-valve nanostructures that comprise the exchange-coupled ferromagnet/ Ru/ferromagnet structure in the free layer have been synthesized by magnetron sputtering. For microobjects (meanders) formed from CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta spin valves with different thicknesses of ruthenium and copper layers, the dependences of the magnetoresistive sensitivity and low-field hysteresis loop shift on the meander strip width have been studied. Sensing elements characterized by high magnetoresistive sensitivity have been manufactured.     

Electrodeposition of NiFe/Cu multilayers from a single bath

NiFe/Cu multilayers were deposited from a single bath in the potentiostatic mode using two different solutions. In solution A, the ionic concentration ratios were Fe²⁺: Ni²⁺: Cu²⁺ 9: 60: 10 and in solution B they were 1: 103: 1. To characterize the layers, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and atomic force microscopy (AFM) were used. SEM results revealed the layered structure of the deposits for relatively thick bilayers. While HRTEM provided direct evidence for the composition modulation across successive layers in the NiFe/Cu nanometer-multilayered structure prepared from solution B. Therefore, the layers prepared from solution B seemed to be more appropriate for giant magnetoresistance (GMR) applications. The effect of stirring during the electrodeposition process of the multilayers was also investigated.     

Investigation on interface of NiFeCr/NiFe/Ta films with high magnetic field sensitivity

NiFeCr/NiFe/Ta films with excellent performance were prepared by magnetron sputtering system.The anisotropic magetoresistance (AMR) value (△R/R) and magnetic filed sensitivity (Sv,Sv=[d(△R/R)/dH]max.) for the 12 nm NiFe film deposited on NiFeCr buffer layer were 3.66％ and 1.42 × 10-4 ％T-1,respectively.The higher Sv of the film is close to that of a spin valve (SV).The microstructure analysis shows that the NiFeCr buffer layer has adopted the same structure with the same interplanar distance as the NiFe layer,inducing a strong NiFe (111) texture,and that the NiFeCr/NiFe interface is quite smooth,leading to a high degree of specular reflection of conduction electrons.Both increase the △R and reduce the R in the film,which lead to the high △R/R.Clean substrate surfaces are critical for preparation of high performance NiFeCr/NiFe/Ta films,and sputter cleaning or pre-deposition of 5 nm amorphous A12O3 layer in the deposition chamber can provide the required clean substrate surfaces for the growth of the buffer layer.     

A new single bath for the electrodeposition of NiFe/Cu multilayers exhibiting giant magnetoresistance behavior

A new single bath for the electrodeposition of ultrathin NiFe/Cu multilayers was developed and magnetoresistance measurements were conducted. Complementary methods such as scanning electron microscopy (SEM), x-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the multilayers. Magnetoresistance measurements indicated that the multilayers grown from this new bath exhibited a giant magnetoresistance (GMR) behavior.     

电迁移促进Cu/Sn-58Bi/Cu焊点阳极界面Bi层形成的机理分析

研究了Cu/Sn-58Bi/Cu对接接头焊点在电流密度为5×103～1.2×104A/cm2条件下钎料基体中阳极界面Bi层的形成机理.电迁移过程中,Bi元素为主要的扩散迁移元素,在电迁移力的作用下由阴极向阳极进行迁移.由于Bi原子的扩散迁移速度比Sn原子要快,促使Bi原子首先到达阳极界面.大量的Bi原子聚集在阳极界面时,形成了压应力,迫使Sn原子向阴极进行迁移,于是在阳极界面处形成了连续的Bi层.阴极处由于金属原子的离去,形成了拉应力,导致了空洞和裂纹在界面处的形成.Bi层的形态主要分为平坦的Bi层和带有凹槽的Bi层.Bi原子进行扩散迁移的通道有三种:Bi晶界、Sn晶界和Sn/Bi界面.随着电流密度和通电时间的增加,Bi层的厚度逐渐增加.电迁移力和焦耳热的产生成为Bi原子扩散迁移的主要驱动力.