磁控溅射Fe/Mo多层膜的巨磁电阻及层间耦合

研究了DC/RF磁控溅射Fe/Mo多层膜的磁电阻特性.在反铁磁性耦合的样品中,观察到了磁电阻比率约为12%的巨磁电阻效应.当Mo层厚度改变时,还观察到了周期约为1.0—1.2nm的层间耦合振荡.另外,F/Mo多层膜的磁电阻比率不仅随Mo层厚度改变出现振荡,而且与Fe层厚度的改变也有着很强的依赖关系. 关键词：     

金属颗粒薄膜巨磁电阻效应的影响因素

研究金属颗粒薄膜的颗粒尺寸、磁性组分等对巨磁电阻效应的影响.在自由电子模型和自旋相关散射理论的基础上，计算了金属颗粒膜体系的电子平均散射势.在计算过程中将自旋相关项与宏观量相联系，得到了巨磁电阻效应与磁性成分比例、颗粒尺寸的关系.磁电阻效应的模拟曲线表明，增加磁性成分比例和减小磁性颗粒尺寸可增强颗粒膜的巨磁电阻效应. 关键词：     

Co/Cu92Mn8/Co结构中的低场巨磁电阻研究

对三明治结构的Co/Cu/Co和Co/Cu₉₂Mn₈/Co系列的巨磁电阻效应进行了研究,发现两者的巨磁电阻均随中介层厚度作周期性振荡,但是接近反相.作为与Co/Cu/Co系统的比较,发现若在Cu基中稀释Mn原子,巨磁电阻随外磁场变化的曲线会有非常大的改变,同时饱和场或开关场也有较大的下降,这意味着有可能为Co/Cu金属多层膜的巨磁电阻的实用化研究开辟出一条新的思路. 关键词：     

磁性金属多层膜中的巨磁电阻效应

在许多磁性金属多层膜系统中都存在巨磁电阻效应，这些系统是由厚度为几个纳米的磁层与非磁层交替重叠构成，出现巨磁电阻效应的必要条件是系统的磁化状态能被外加磁场所改变。该效应的物理是传导电子在界面处或磁层内的所谓自旋相关散射，层间耦合随隔离层厚度变化而振荡的现象，在隔离层为非磁过渡金属和贵金属的系统中普遍存在，自旋阀多层结构在信息存储技术中磁电阻“读出”头方面极具应用前景。     

磁电子学讲座第三讲 磁性金属多层膜中的巨磁电阻效应

在许多磁性金属多层膜系统中都存在巨磁电阻效应，这些系统是由厚度为几个纳米的磁层与非磁层交替重叠而构成．出现巨磁电阻效应的必要条件是系统的磁化状态能被外加磁场所改变．该效应的物理原因是传导电子在界面处或磁层内的所谓自旋相关散射．层间耦合随隔离层厚度变化而振荡的现象，在隔离层为非磁过渡金属和贵金属的系统中普遍存在．自旋阀多层结构在信息存储技术中磁电阻“读出”头方面极具应用前景．     

多层金属圆柱线中量子输运的表面和界面散射效应

考虑了量子尺寸效应以及来自杂质、粗糙表面和粗糙界面三方面的散射,运用量子统计的格林函数方法和久保公式,计算多层金属圆柱线中的各种散射电导率.计算结果表明,在杂质、表面和界面的弱散射极限下,系统总电导率等于各个子能级通道的电导率之和,而各子能级通道中杂质、表面和界面产生的散射率是可相加的. 关键词：     

磁多层金属系统的界面反射效应

考虑到磁多层金属系统中的粗糙界面散射效应,运用量子统计的格林函数方法和久保理论,计算磁多层金属系统的单粒子传播格林函数和电导率.所得结果依赖于电子在界面处的反射波幅和空间尺寸,并能展示巨磁电阻的主要实验特征. 关键词：     

Fe/Cr磁性多层膜的制备及其磁电阻测定

利用磁控溅射制备了不同非磁性层厚度的Fe/Cr多层磁性薄膜系统,利用四探针法测定了该多层膜系统在不同磁场下磁电阻效应,用饱和场法给予佐证,溅射制备的多层膜系统饱和场明显地随Cr层厚度增加而衰减振荡,得出了Fe/Cr多层膜的铁磁反铁磁耦合的交换耦合强度随非磁性层厚度变化的物理规律.     

金属磁性多层膜的新颖特性──巨磁电阻效应

磁性和非磁性层交替重构成的金属磁性多层膜常具有巨磁电阻效应，其中每层膜约几个纳米厚。出现巨磁电阻效应的基本条件是：在外磁场下相邻磁层磁化强度取向发生对变化。巨磁电阻效应的物理起源是，其自旋与局域磁化强度平行和反平行的电子受到的散射不同，散射的不同既要嗵来自获射中收的特性，又可能源于两种自旋电子的能态密度的差异。由于信息存储技术中磁电阻“读出”磁头有巨大的应用前景，巨磁电阻效应引起了人们的极大兴趣。     

磁性多层膜的巨磁电阻随铁磁和非磁层厚度变化的唯象理论计算

根据唯象理论，并采用以铁磁─非磁混合层代替铁磁／非磁层界面的理论方法，计算了Ｆｅ／Ｃｒ多层膜的巨磁电阻随铁磁和非磁层厚度的变化关系与实验结果做了比较，发现它们符合得较好．还绘出了巨磁电阻随铁磁和非磁层厚度变化的二元函数图 关键词：     

Quantum analytical theory for giant magnetoresistance in magnetic multilayered film systems

Taking into account the quantum size effects and considering three types of scattering from bulk impurities, rough surfaces, and rough interfaces, we use the quantum-statistical Green's function approach and Kubo theory to calculate the giant magnetoresistance (GMR) in magnetic multilayered structures. Our calculation can reproduce the main features of GMR experiments, including the oscillations of GMR with nonmagnetic thickness, and the GMR increases with increasing number of bilayers N of the (Fe/Cr)_N/Fe system and others. As well, the question whether or not the scattering rates due to the impurities, surfaces, and interfaces add up is also addressed to.     

Influence of Interface Scattering and Quantum Size Effect on the Giant Magnetoresistance in a Magnetic Sandwich Structure

An analytical Green's function approach to the study of the electronic transport in a magnetic sandwich structure is presented. Taking into account the quantum size effect and considering three types of scattering from bulk impurities, rough surface, and two rough interfaces, we calculate the one-particle Green's function and the in-plane conductivity, yield a new formula for conductivity. It is found that (i). the magnetoresistance in the ultrathin spin-value sandwiches shows oscillation as a function of thickness with a period of half Fermi wavelength; (ii) in the thin-film limit and the lowest-order approximation of the surface and interface scatterings, the total conductivity is given by a sum of conductivities of all the subbands and the two spin channels, for each subband and each spin channel the scattering rates due to the impurities, surfaces and interfaces are additive.     

Magnetic depth profiling of Fe/Au multilayer using neutron reflectometry

We present unpolarized and polarized neutron reflectometry data on Fe/Au multilayer sample for characterizing the layer structure and magnetic moment density profile. Fe/Au multilayer shows strong spin-dependent scattering at interfaces, making it a prospective GMR material. Fe/Au multilayer with bilayer thickness of 130 Å was grown on Si substrate by RF magnetron sputtering technique. Unpolarized neutron reflectivity measurement yields nuclear scattering length density profile. The magnetic scattering length density profile has been obtained from polarized neutron reflectivity measurements.     

Quantum Analytical Theory for Giant Magnetoresistance in Magnetic Multilayered Cylindrical Systems

Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces,we use quantum-statistical Green‘s function approach and Kubo theory to calculate the electronic conductivity and the giant magnetoresistance in magnetic multilayered cylindrical systems.It is found that in the limit of weakly scattering from impurities surface and interfaces,the total conductivity is given by a sum of conductivities of all the subbands and two spin-channels.For each subband and each spin-channel the scattering rate due to the impurities,surface and interfaces is added up.     

Effects of oxidation and cluster distribution on thermal and magnetotransport properties of mechanically alloyed Co–Cu powders

Thermal and magnetotransport properties of mechanically alloyed Co₃₀Cu₇₀ powders of three different milling times are studied. Both milling and annealing bring about oxidation of the samples. The powders show exothermic behaviors corresponding to the lattice-recovery process. Different milling times and annealing temperatures give rise to different exothermic peaks because of oxidation and the cluster distribution. At room temperature, the compressed powders show, on average, up to 11% giant magnetoresistance (GMR) under 10 kOe with sharp switching. The results may be understood in terms of spin-dependent scattering across Co/oxide/Cu interfaces. Annealing reduces the resistance but does not promote the GMR. By annealing at 400 °C, the GMR is entirely suppressed as the magnetic content is largely replaced by oxides. PACS 72.15.Eb; 75.47.De; 75.47.Np     

The Rayleigh hypothesis in scattering off photonic crystal interfaces

We examine the Rayleigh hypothesis in the context of scattering of light off photonic crystal interfaces. First, the hypothesis - which was initially suggested for scattering of waves off rough surfaces between homogeneous media - is rephrased to apply to photonic crystal interfaces. Next, an exact and explicit functional form is presented that maps plane photonic crystal surfaces to periodic rough surfaces in free space, so that known criteria for the validity of the Rayleigh hypothesis for scattering at rough surfaces can be applied directly to scattering at the photonic crystal surfaces. The same map also allows the scattering problem to be solved exactly.     

Research on synthetic aperture radar imaging technology of one-dimensional layered rough surfaces

A quick and exact imaging method for one-dimensional layered rough surfaces is proposed in this paper to study the scattering characteristics of a layered medium that exists widely in nature.The boundary integral equations of layered rough surfaces are solved by using the propagation-inside-layer expansion combined with the forward and backward spectral acceleration method(PILE+FB-SA),and the back scattering data are obtained.Then,a conventional synthetic aperture radar(SAR) imaging procedure called back projection method is used to generate a two-dimensional(2D) image of the layered rough surfaces.Combined with the relative dielectric permittivity of realistic soil,the random rough surfaces with Gauss spectrum are used to simulate the layered medium with rough interfaces.Since the back scattering data are computed by using the fast numerical method,this method can be used to study layered rough surfaces with any parameter,which has a great application value in the detection and remote sensing areas.     

金属双层膜中量子输运的表面和界面散射效应

运用格林函数的解析方法研究金属双层膜的电子输运.考虑了量子尺寸效应和来自杂质、粗糙表面和粗糙界面三方面的散射,计算单粒子格林函数和平行电导率,得到了金属双层膜的电导公式.计算结果表明,在薄膜极限和表面及界面散射的最低阶近似下,系统总电导率等于各子能级通道的电导率之和,而各子能级通道中杂质、表面和界面产生的散射率是可相加的. 关键词：     

Correlation between structural and giant magnetoresistance properties of Fe–Ag nanogranular films

Fe _x Ag_1?x granular thin-films, with the atomic Fe concentration, x, ranging from 0 up to 0.5, were deposited by dc magnetron co-sputtering. The giant magnetoresistance (GMR) intensity is maximum at x _I  = 0.32, while the maximum of GMR efficiency, γ, i.e., the change of GMR intensity for a unit change of reduced squared magnetization, is observed at x _γ = 0.26. Owing to the spin-dependent scattering features, the GMR intensity and γ depend on both the concentration and the arrangement of the magnetic material. Therefore, to explain the difference between x _I and x _γ and to understand how the structural properties affect the magnetoresistive behaviour, we performed magnetization, Mössbauer and X-ray diffraction measurements as a function of x. X-ray data indicate that the granular films exhibit three different regimes: for x < 0.2, they can be described as a Fe–Ag solid solution; for 0.2 < x < 0.32 the Fe–Ag solid solution is still observed and very small Fe precipitates are found; finally, for x > 0.32, a Fe–Ag saturated solid solution is detected, containing bcc Fe clusters whose size is about 10 nm. Differently, for all the concentrations, magnetization data show the presence of Fe precipitates, whose size increases with x, and the Mössbauer investigation confirms this picture. We find that the samples grown at x = x _γ display the finest Fe dispersion within the Ag matrix, as the Fe–Ag solid solution is nearly at saturation and the Fe cluster size is of the order of a few nanometers; this arrangement possibly maximizes the magnetic/non-magnetic interface extension thus enhancing the GMR efficiency. If x is slightly increased, the increase in total Fe content compensates the GMR efficiency reduction, so the GMR intensity maximum is observed.