GdFeCo/AIN/DyFeCo静磁耦合多层薄膜磁化方向转变的研究

对GdFeco／AIN／DyFeco静磁耦合多层薄膜变温磁化方向变化进行了研究。结果表明读出层GdFeCo随温度上升从平面磁化转变成垂直磁化，转变过程中受饱和磁化强度(M)和有效各向异性常数影响，但主要受饱和磁化强度(M)的影响。在高温时读出层的磁化强度很小，退磁场能减小，在静磁耦合作用下，使GdFeCo读出层的磁化方向发生转变，而且磁化方向的转变在较小的温度范围内变化较快。     

Fe膜及磁场沉积对TbDy-Fe膜磁伸性能的影响

为了提高TbDv-Fe膜的低场磁敏性,采用离子束溅射沉积(IBSD)法制备TbDy-Fe超磁致伸缩薄膜,分别研究了纯Fe膜与TbDy-Fe单层膜、TbDy-Fe/Fe耦合多层膜的复合及磁场下溅射沉积对TbDy-Fe膜磁致伸缩性能的影响;用振动样品磁强计(VSM)测试薄膜磁滞回线,用电容位移测量仪测试薄膜悬臂梁自由端偏转量,并计算出磁致伸缩系数λ.结果表明,由IBSD法制备的纯Fe膜、TbDy-Fe单层膜、TbDy-Fe/Fe复合膜的易磁化轴均平行于膜面,TbDy-Fe/Fe复合膜在低场下的磁化强度与磁导率均高于TbDy-Fe单层膜(在100 kA/m时,TbDy-Fe/Fe复合膜的磁化强度比TbDy-Fe单层膜高173%).纯Fe膜分别与TbDy-Fe单层膜、TbDy-Fe/Fe耦合多层膜进行复合均可提高薄膜磁致伸缩性能;磁场下溅射沉积所得180 nm纯Fe膜 640 nmTbDy-Fe/Fe耦合多层膜,由于在其膜面内短轴方向产生感生磁各向异性,从而使磁致伸缩性能得到进一步的提高,在150 kA/m的磁场下它的λ值可达到650×10-6.     

退火温度对NiZn铁氧体薄膜性能的影响

用溶胶-凝胶(Sol-Gel)法在Si(100)基片上沉积了NiZn铁氧体薄膜,研究了退火温度对薄膜结构和磁性能的影响.XRD研究表明,薄膜具有立方尖晶石结构,但当退火温度为900 ℃时,有SiO2相出现,发生了明显的Si扩散.原子力显微镜(AFM)究表明,退火温度升高,薄膜晶粒尺寸逐渐变大,粗糙度相应增加.随着退火温度的升高,薄膜的饱和磁化强度(Ms)呈先增加后降低的趋势,而矫顽力(Hc)与Ms变化相反.当退火温度为700 ℃时,薄膜具有最优磁性能,Ms=360×103 A/m,Hc=6 764 A/m.     

稀土—过渡族金属非晶态磁光材料信号读出特性研究

在计算RE-TM饱和磁化强度和温度关系曲线的基础上,本文建立了一种适用于计算磁光光盘读出信号质量与读出激光功率关系的方法,对经优化的四层膜结构实例给出了最佳读出激光功率,并讨论了稀土含量变化时,对最佳读出激光功率和信噪比的影响,结果与有关的实验规律相吻合。     

Cr离子取代Co2Z六角铁氧体的磁特性研究

采用固相反应法制备了Cr离子取代的Co2Z平面六角结构(Sr3Co2Fe24-xCrxO41)软磁铁氧体,并对其磁特性进行了研究。分析了样品的物相组成,并计算了样品的晶格常数;用扫描电镜分析了样品的形貌特征;测试了样品的磁滞回线。实验结果表明,掺杂Cr离子后,晶格常数变化不大,当Cr取代量x≥0.3时,Z相开始分解;在x≤0.2时,随着x的提高,样品的饱和磁化强度(Ms〖WTBZ〗)逐渐增加;当x＞0.2时,随着x的增加,样品的饱和磁化强度减小。由此可见,通过掺入适量的Cr离子可以提高Z型六角铁氧体的磁特性。     

(TbBi)3GaxFe5-xO12薄膜/(TbYbBi)3Fe5O12晶体复合结构的生长和在光通信波段的磁光性能

用助熔剂法生长出掺Bi复合稀土铁石榴石晶体((TbYbBi)3Fe5O12),用(TbYbBi)3Fe5O12替代传统的无磁性Gd3Ga5O12晶体作基底液相外延掺Bi稀土铁鎵石榴石薄膜((TbBi)3GaXFe5-XO12).测量了Tb0.87Yb1.62Bi0.51Fe5O12晶体和Tb2.43Bi0.57Ga0.12Fe4.88O12薄膜/Tb0.87Yb1.62Bi0.51Fe5O12晶体复合结构材料在光通信波段(波长λ=1500-1620nm)处的光透射谱(T)、饱和磁化强度(Ms,0.5×106A/m)、法拉第旋转温度系数(FTC,5×10-5/K)和法拉第旋转波长系数(FWC,0.05%/nm).所得结果表明:Tb2.43Bi0.57Ga0.1Fe4.9O12薄膜/Tb0.87Yb1.62Bi0.51Fe5O12晶体复合结构材料的综合性能适用于宽带和温度稳定的光隔离器及其他光通讯器件.     

关于磁液饱和磁化强度的讨论

磁液是一种亚铁磁性材料,在外部磁场的作用下,磁液中的磁性微粒会按照外磁场的方向有序排列,而使其每单位容积中的磁矩达到最大值,即磁液的饱和磁化强度Ms.基于此,探讨磁液的饱和磁化强度、饱和磁化强度的测量及其在工程中常用的单位.     

超细Co/Cu纳米多层膜磁性研究

利用磁控溅射方法制备了纳米Co/Cu多层膜。利用扫描探针显微镜(SPM)观测了其表面形貌和磁畴结构,并通过振动样品磁强计(VSM)测量了磁性。结果表明,薄膜的微结构和磁性随非磁性层厚度的变化有着非常显著的变化。超细Co颗粒构造的多层膜样品,颗粒尺寸逐渐增大,磁畴尺寸先减小后增大,最后发生明显的聚集。磁性金属和非磁性金属的比例对多层膜之间的交换耦合相互作用有显著影响。平行膜面方向上的饱和场明显小于垂直膜面方向。当体积比约为1∶80时,平行膜面方向饱和场为95.9 kA/m,垂直方向饱和场为328.1 kA/m。此时两个方向上的饱和场、剩磁、矫顽力和磁滞损耗均为最小值。     

微波静磁波模式特性分析

全面分析了磁光薄膜波导中磁化方向对微波静磁波传播模式的影响。给出了不同模式的静磁波色散方程和带宽的一般表达式,首次完整地展现了静磁波的模式分布图。所得结论可用于分析倾斜磁场在改善基于静磁波的新型磁光B ragg器件衍射性能方面所起的作用。     

Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5合金的热性能、微观结构及磁性能研究

采用单辊快淬法制备了Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5非晶合金,在不同温度下对两种合金进行了热处理。利用差热分析仪(DTA)、X射线衍射仪(XRD)和振动样品磁强计(VSM)等仪器对两种合金的热性能、微观结构和磁性能进行了测试分析。结果表明在Fe78Co2.5Zr7Nb2B10Cu0.5合金的晶化过程中存在预结晶效应,而在Fe81Zr7Nb2B10合金的晶化过程中没有。Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5合金经803 K退火后,分别有α-Fe和α-Fe(Co)相从非晶基体中析出。随退火温度的升高,两种合金的比饱和磁化强度(Ms)变化趋势相似,但矫顽力(Hc)变化趋势明显不同。     

Mn／Sb多层膜的磁性和磁光特性

用超高真空蒸发技术在GaAs(100)和玻璃衬底上生长不同厚度Mn／Sb多层膜，并经短时间热退火(～1，20min)．磁化强度测量显示具有很强的室温铁磁特性．当多层膜厚度从700l增至1600A时，饱和强度增加了近一倍，极向和纵向克尔角也增加了，但不到一倍．这表明磁化强度和克尔角两者均依赖于多层摸的厚度，但不是简单的正比于厚度的关系．增加Mn／Sb多层膜的厚度能增强饱和磁化强度和极向和纵向克尔饱和角．X射线衍射谱图结果表明高质量单晶结构的Mn／Sb多层膜能用超高真空蒸发技术生长，对较厚的多层薄膜，热退火的时间可很短(约1min)．     

GaAs衬底上Mn／Sb多层铁磁膜的磁光克尔效应

利用超高真空电子束蒸发技术GaAs(100）上生长Mn/Sb多层膜,并经短时间热退火处理分别研究了其退火前后的磁性、磁光克尔效应及相应规律,退火前Mn/Sb膜在室温下即具有较强的铁磁特性,其易磁化轴在膜面内,样品表面由密集的岛状铁磁颗粒组成,未能观测到纵向（H//平面）克尔效应,经350℃、20min退火的样品显示了最大饱和磁化强度Ms和最小矫顽力Hc,X射线衍射测量表明膜为MnSb单晶并具有均匀的铁磁特性,能观测到显著的要有向和纵向磁光克尔效应,其随磁场变化表现出相应于磁化强度的磁带行为。     

Ferromagnet/Superconductor Hybridization for Magnonic Applications

In this work, a new hybridization of superconducting and ferromagnetic orders is demonstrated, promising for magnonics. By measuring the ferromagnetic and spin wave resonance absorption spectra of a magnetostatically coupled permalloy/niobium bilayer at different temperatures, magnetostatic spin wave resonances with unconventional dispersion are observed. The mechanism behind the modified dispersion, confirmed with micromagnetic simulations, implies screening of the alternating magnetostatic stray fields of precessing magnetic moments in the ferromagnetic layer by the superconducting surface in the Meissner state.     

Joule heating dominated fracture behavior change in micro-scale Cu/Sn-3.0Ag-0.5Cu/Cu(Ni) joints under electro-thermal coupled loads

Joule heating dominated fracture position transition from the interface between the solder and the intermetallic compound (IMC) layer to the solder matrix occurs in micro-scale Cu/Sn-3.0Ag-0.5Cu/Cu(Ni) joints under electro-thermal coupled loads with a high current density and increasing temperature. The interfacial fracture is triggered by localized-melting of the solder induced by current crowding at grooves of the interfacial IMC grains and driven by the strain mismatch between the solder and the interfacial IMC layer, while fracture in the solder matrix is caused by matrix bulk melting and the constraint effect from the interfacial IMC layer-substrates.     

镀镍碳管的结构及磁性能研究

以自制的多壁碳纳米管为原料,利用化学镀的方法制得镀镍碳管。并用X射线衍射仪、透射电镜、扫描电镜及能量色散谱仪对其进行了表征,结果表明:碳管表面镀镍层中x(Ni)达到68.8%,磁性能分析表明,镀镍碳管饱和磁化强度达到13067Am2/kg,热处理后饱和磁化强度达到257733Am2/kg。最后,对其表面镀层进行了热分析。     

Symmetry-Mismatch-Induced Ferromagnetism in the Interfacial Layers of CaRuO3/SrTiO3 Superlattices

By modifying the entangled multi-degrees of freedom of transition-metal oxides, interlayer coupling usually produces interfacial phases with unusual functionalities. Herein, a symmetry-mismatch-driven interfacial phase transition from paramagnetic to ferromagnetic state is reported. By constructing superlattices using CaRuO₃ and SrTiO₃, two oxides with different oxygen octahedron networks, the tilting/rotation of oxygen octahedra near interface is tuned dramatically, causing an angle increase from ≈150° to ≈165° for the Ru O Ru bond. This in turn drives the interfacial layer of CaRuO₃, ≈3 unit cells in thickness, from paramagnetic into ferromagnetic state. The ferromagnetic order is robust, showing the highest Curie temperature of ≈120 K and the largest saturation magnetization of ≈0.7 µ_B per formula unit. Density functional theory calculations show that the reduced tilting/rotation of RuO₆ octahedra favors an itinerant ferromagnetic ground state. This work demonstrates an effective phase tuning by coupled octahedral rotations, offering a new approach to explore emergent materials with desired functionalities.     

Tuning a Binary Ferromagnet into a Multistate Synapse with Spin–Orbit‐Torque‐Induced Plasticity

Ferromagnets with binary states are limited for applications as artificial synapses for neuromorphic computing. Here, it is shown how synaptic plasticity of a perpendicular ferromagnetic layer (FM1) can be obtained when it is interlayer exchange‐coupled by another in‐plane ferromagnetic layer (FM2), where a magnetic field‐free current‐driven multistate magnetization switching of FM1 in the Pt/FM1/Ta/FM2 structure is induced by spin–orbit torque. Current pulses are used to set the perpendicular magnetization state, which acts as the synapse weight, and spintronic implementation of the excitatory/inhibitory postsynaptic potentials and spike timing‐dependent plasticity are demonstrated. This functionality is made possible by the action of the in‐plane interlayer exchange coupling field which leads to broadened, multistate magnetic reversal characteristics. Numerical simulations, combined with investigations of a reference sample with a single perpendicular magnetized Pt/FM1/Ta structure, reveal that the broadening is due to the in‐plane field component tuning the efficiency of the spin–orbit torque to drive domain walls across a landscape of varying pinning potentials. The conventionally binary FM1 inside the Pt/FM1/Ta/FM2 structure with an inherent in‐plane coupling field is therefore tuned into a multistate perpendicular ferromagnet and represents a synaptic emulator for neuromorphic computing, demonstrating a significant pathway toward a combination of spintronics and synaptic electronics.     

A Study of Phonon Transport in Si/Ge Superlattice Thin Films Using a Fast MC Solver

We employ a fast Monte Carlo solver, which takes advantage of the geometric symmetry existent in the system to reduce the computational effort, to investigate the phonon transport phenomena in the cross-plane and in-plane directions of Si/Ge superlattice thin films. The simulation results show that the heterogeneous interfaces perpendicular to the heat flow direction create a much stronger thermal resistance than the parallel ones. The cross-plane and in-plane thermal conductivities of a Si/Ge superlattice thin film increase monotonically with the smoothness of the interfaces and the superlattice period. Most of all, a minimum of the in-plane thermal conductivity is observed as the ratio of the layer thicknesses is varied for fixed period. This is due to the effective layer thermal conductivities being determined not only by the phonon intrinsic properties but also by the strong interface scattering. A detailed examination shows that the minimum appears when the effective layer thermal conductivities of the Si and Ge layers are about the same.     

In掩膜层超分辨光盘的读出研究

在超分辨光存储技术中,掩膜层材料是决定其性能优劣的关键。In薄膜可以作为掩膜层用来实现超分辨信息点的动态读出。采用直流磁控溅射法制备不同厚度的In薄膜,用台阶仪测量薄膜厚度随时间的变化关系,用原子力显微镜观察不同厚度薄膜样品的表面形貌。在预刻有尺寸为390nm信息点的光盘盘基上制备In薄膜,从而形成In掩膜超分辨光盘。利用光盘动态测试仪进行动态读出,最高读出载噪比(CNR)达到26dB。为了进一步分析超分辨动态读出的物理机理,采用变温椭圆偏振光谱仪测量In薄膜在不同温度下的光学常数,得到In薄膜在不同温度下的反射率和吸收系数。分析表明In掩膜超分辨光盘的读出机理符合孔径型超分辨读出模型。