STRUCTURES,Pd SPACER POLARIZATION AND MAGNETIC PROPERTIES OF Co-Nb/Pd MULTILAYERS

Magnetic multilayers ［Co-Nb(1.5 or 3.6 nm)/Pd(x nm)］₄₀ were fabricated by radio frequency sputtering synthesis.The structures and magnetic properties of the Co-Nb/Pd multilayers were studied by X-ray diffraction,vibrating sample magnetometer,torque magnetometer and ferromagnetic resonance measurements.The oscillatory dependence of the phase structure,the strain,the ferromagnetic inter layer coupling and the spacer polarization of multilayers on the increase of Pd spacer thickness was observed.The relationship among phase structure,strain,inte rlayer coupling and the polarization of Pd spacers was discussed.The magnetic polarization of Pd spacers will enhance the ferromagnetic coupling between magnetic layers and will restrain antiferromagnetic coupling to occur.The spin dependent electron transport along the normal direction of multilayers and its exchange interaction play key roles in causing these oscillatory behaviors.     

FORMATION AND MAGNETIC PROPERTIES OF Dy2Fe17-xMnxC(x = 0-17) PREPARED BY ARC-MELTING

We report on alloys formed by replacing iron with manganese in the compound Dy₂Fe₁₇C_1.0 Samples were characterized by X-ray diffraction and magnetic measure-ments, The 2:17-type structure can be crystallized in the whole range of manganese substitution. The Curie temperature of the series of Dy₂Fe_17-xMn_xC_1.0(x= 0-17) drops down considerably from 515K for x = 0 to about 20K for compounds with high manganese concentration, and the compensation point was observed in a narrow range of x≈4-6. The rapid decrease of the magnetization shows that the manganese substitution is not a simple magnetic dilution to the transition-metal sublattice mo-ment, it indicates that the moment of Mn may be antiparallel to that of Fe. The field dependence of the magnetization of Dy₂Fe_17-xMn_xC_1.0 may indicate the existence of the nonlinear magnetic structure for the samples with high Mn conoentrations.     

STRUCTURE, MAGNETIC PROPERTIES AND GIANT MAGNETORESISTANCE OF YMn6Sn6-xGax (x=0-0.6) COMPOUNDS

Structure, magnetic and transport properties of YMn₆Sn_6-xGa_x (0≤x≤0.6) compounds with a HfFe₆Ge₆-type structure were investigated. It was found that the Ga substitution leads to a contraction of the unit-cell volume. A transition from an antiferromagnetic to a ferromagnetic (or ferrimagnetic) state can be observed for samples (0.1≤x≤0.2) with increasing temperature. The antiferro-ferromagnetic transition for samples with x≤0.2 can also be induced by an external field. The required field is very low, and decreases with increasing Ga concentration. More Ga concentration (x≥0.3) leads to the samples being ferromagnetic in the whole temperature range below the Curie temperature. The Ga substitution weakens the interlayer magnetic coupling between the Mn spins. Corresponding to the metamagnetic transition, a magnetoresistance as large as 32% under a field of 5 T was observed at 5 K for the sample with x=0.2.     

ELECTROREFLECTANCE SPECTRA OF GexSi1-x/Si STRAINED LAYER MULTIPLE-QUANTUM WELLS

We have investigated the optical transitions above the fundamental gap of a set of Ge_xSi_1-x/Si strained layer multiple-quantum wells by electroreflectance (ER). The sam-ples were grown by molecular beam espitaxy (MBE). The thickness of the strained layer of Ge_xSi_1-x was 5nm with Ge concentration x in the range from 0.4 to 0.5, and the Si barrier layer greater than 16nm. Considering the energy shift caused by strain and quantum well confinement, we were able to clearly recognize the transitions from different quantum well structures associated with the critical points E₀, E′₀, and E₁. The transitions of the critical points E₀ and E′₀, which are very weak in bulk mateials, are apparently enhanced in the quantum well structures.     

RAMAN SCATTERING INTENSITIES OF FOLDED LONGITUDINAL ACOUSTIC PHONONS IN GexSi1-x/Si SUPERLATTICES

In terms of photoelastic mechanism we have investigated the Raman scattering intensities of the folded longitudinal acoustic (FLA) phonons in Ge_xSi_1-x/ Si superlattices (SLs), taking into account the differences between the acoustic and photoelastic parameters of the two constituents in the SLs. The relative intensities calculated for the FLA phonons are in excellent agreement with the experimental results at the frequencies up to about 50 cm^-1. The broadening of the linewidth arising from the so called strong acoustic attenuation, which was reported previously located around the frequency 15 cm^-1 in Ge_xSi_1-x/Si SLs(x≈0.5), has not been observed in this work.     

MAGNETIC POLARIZATION OF SPACER Pd LAYER AND MAGNETIC PROPERTIES OF Co/Pd MULTILAYERS

Magnetic multilayers［Co(1.5 nm)/Pd(x nm)］₄₀ grown by rf sputtering were studied by X-ray diffraction,vibrating sample magnetometer,torque magnetomet er and magnetoresistance measurements.The dependences of the interfacial roughne ss and the structure perfectness of Co/Pd multilayers on the spacer Pd layer thi ckness have been revealed from X-ray diffraction data.An oscillatory variation of saturation magnetization versus the thickness of the Pd spacer was observed.A similar oscillatory behavior in the dependence of its magnetic anisotropy on the thickness of the Pd spacer was observed.It is suggested from these two phenomen a that the magnetic polarization of Pd spacers oscillates between ferromagnetic and antiferromagnetic polarization with the increase of Pd spacer thickness under a RKKY-like interaction.Evidence is found for the antiferromagnetic polarization of the inner part of the Pd spacer.The antiferromagnetic coupling between two Co layers and giant magnetoresistance effect in Co/Pd multilayer system were not observed.The relationship among structure,interlayer coupling and magnetic polarization effect of the Pd spacer was discussed.     

Magnetic properties and magnetoresistance effect of Y1-xGdxMn6Sn6 (x=0－1) compounds

The magnetic properties and magnetoresistance effect of Y_1-xGd_xMn₆Sn₆ (x=0－1) compounds have been investigated by magnetization and resistivity measurements in the applied field range (0－5 T). Compounds with x=0.4－1 display ferrimagnetic behaviours in the whole magnetic ordering temperature range, while compounds with x=0－0.2 display a field-induced metamagnetic transition, and the threshold fields decrease with increasing Gd content. The compounds with x=0.1－0.2 undergo an antiferromagnetic to ferromagnetic transition with increasing temperature. The cell-parameter a and c and cell-volume V of compounds (x=0－1) increase with increasing Gd content. It was found that the saturation magnetization M_s of the compounds (x=0.4－1) decreases, while the ordering points of the compounds (x=0－1)increase with increasing Gd content. A large MR effect was observed in the compound with x=0.2, and the maximum absolute value of MR at 5 K under 3 T is close to 19.3%.     

The effect of Si content on the martensitic transfor-mation temperature of Ni55.5e18Ga26.5-xSix alloys

This paper investigates the effects of substitution of Si for Ga on the martensitic transformation behaviours in Ni-Fe-Ga alloys by using optical metallographic microscope and differential scanning calorimetry (DSC) methods. The structure type of Ni_55.5Fe₁₈Ga_26.5-xSi_x alloys is determined by x-ray diffraction (XRD), and the XRD patterns show the microstructure of Ni-Fe-Ga-Si alloys transformed from body-centred tetragonal martensite (with Si content x = 0) to body-centred cubic austenite (with x = 2) at room temperature. The martensitic transformation temperatures of the Ni_55.5Fe₁₈Ga_26.5-xSi_x alloys decrease almost linearly with increasing Si content in the Si content range of x ≤ 3. Thermal treatment also plays an important role on martensitic transformation temperatures in the Ni-Fe-Ga-Si alloy. The valence electronic concentrations, size factor, L2₁ degree of order and strength of parent phase influence the martensitic transformation temperatures of the Ni-Fe-Ga-Si alloys. An understanding of the relationship between martensitic transformation temperatures and Si content will be significant for designing an appropriate Ni-Fe-Ga-Si alloy for a specific application at a given temperature.     

Magnetocaloric effects in Mn1.35Fe0.65P1-xSix compounds

The structural and magnetocaloric properties of Mn_1.35Fe_0.65P_1-xSi_x compounds are investigated. The Si-substituted compounds, Mn_1.35Fe_0.65P_1-xSi_x with x = 0.52, 0.54, 0.55, 0.56, and 0.57, are prepared by high-energy ball milling and the solid-state reaction. The X-ray diffraction shows that the compounds crystallize into the Fe₂P-type hexagonal structure with space group P62m. The magnetic measurements show that the Curie temperature of the compound increases from 253 K for x = 0.52 to 296 K for x = 0.56. The isothermal magnetic-entropy change of the Mn_1.35Fe_0.65P_1-xSi_x compound decreases with the Si content increasing. The maximal value of the magnetic-entropy change is about 7.0 J/kg稫 in the Mn_1.35Fe_0.65P_0.48Si_0.52 compound with a field change of 1.5 T. The compound quenched in water possesses a larger magnetic entropy change and a smaller thermal hysteresis than the non-quenched samples. The thermal hysteresis of the compound is less than 3.5 K. The maximum adiabatic temperature change is about 1.4 K in the Mn_1.35Fe_0.65P_0.45Si_0.55 compound with a field change of 1.48 T.     

Structural and magnetic properties of Dy2Co17—xMnx compounds

Using x-ray diffraction and magnetic measurements, we have studied the structural and magnetic properties of Dy₂Co_17-xMn_x (x=0∽5) compounds with a rhombohedral Th₂Zn₁₇-type structure. With an increasing Mn concentration x, the unit-cell volume V was found to increase linearly. The Curie temperature T_c decreases linearly, and the saturation magnetization M_s at 5K first increases slightly for x<1, then decreases rapidly for x>1 with a further increase of Mn concentration x. In compounds for x=1～3, a spin reorientation was found. A magnetic diagram of the compounds is given.     

用于电压基准的Nb/NbxSi1-x/Nb约瑟夫森单结的研制

现代可编程约瑟夫森电压基准的核心器件是约瑟夫森结阵.目前最具有优势的约瑟夫森结阵是 Nb/Nb_xSi_1-x/Nb材料的结阵. Nb/Nb_xSi_1-x/Nb材料的约瑟夫森结 具有三层薄膜的制作过程简便, Nb和Nb_xSi_1-x刻蚀工艺相同以及Nb_xSi_1-x 势垒层成分可调等优点.中国计量科学研究院设计制作了Nb/Nb_xSi_1-x/Nb约瑟夫森单结. 通过在4.2 K低温下对所做单结进行直流电流-电压特性测量,观测到了清晰的超导隧穿电流和 从零电压态向电压态的跳变,最后就测量结果进行了分析讨论.此项工作属于国内首个开展 Nb/Nb_xSi_1-x/Nb材料约瑟夫森单结研究的工作.     

Na3Zr2-xInxSi2-xP1+xO12系统的组成、结构和离子电导的关系

用固相反应、X射线衍射、金相显微镜观察、测定比热和复平面阻抗谱的方法研究了Na₃Zr_2-xIn_xSi_2-xP_1+xO₁₂系统。在此系统中存在两种固溶体:单斜固溶体(0≤x<0.8)和三方固溶体(0.8≤x≤1.8)。即从x=0.8的组成开始,NASICON型Na₃Zr_2-xIn_xSi_2-x 关键词：     

Hydrogen-controlled interlayer exchange coupling in Fe/LaHx multilayers

Magneto-optic Kerr magnetometry and neutron reflectometry reveal that Fe layers exhibit magnetic exchange coupling through LaH_x spacer layers. Ferromagnetic and antiferromagnetic coupling is observed on multilayers of these materials depending on the thickness of the hydride layers, but without oscillatory behavior. Starting from metallic La dihydride spacer layers the effect of dissolving increasingly more hydrogen was examined. Sign and value of the coupling depend crucially on the hydrogen content x. The coupling can be inverted from antiferromagnetic to ferromagnetic and vice versa. These alterations are due to modifications of the electronic structure of the hydride. When the hydrogen absorption saturates the hydride layers become insulating and the exchange coupling is likely to disappear. In this final state the multilayers are always characterized by a very soft ferromagnetic rectangular hysteresis curve. Upon removal of the hydrogen to the initial concentration the original magnetic structure is restored.     

用脉冲激光方法在Si(100)上沉积的Cox-C1-x颗粒膜及其磁电阻效 应

利用脉冲激光沉积方法在Si(100)上制备了Co_x-C_1-x颗粒膜，并研 究了其正磁电阻 效应.实验结果表明，样品在室温下的正磁电阻效应要远远高于低温下的正磁电阻效应；Co _0.02-C_0.98样品具有最大的室温正磁电阻效应，在外加磁场B=1T时 ，其磁电阻 率MR=22%；随着Co含量的增加，Co_x-C_1-x颗粒膜的正磁电阻效应呈 减小趋势.样品 的MR-B的曲线与传统的多 关键词： 正磁电阻效应 x-C_1-x颗粒膜')" href="#">Co_x-C_1-x颗粒膜 脉冲激光沉积     

Pt1-xCux/Co多层膜的结构和磁性

系统地研究了Pt_1-xCu_x/Co多层膜的结构与磁性.除了特定的x=0.10—0.15区间外，在Cu浓度区间x=0.04—0.30内，随着中介Pt层内Cu浓度的增加，导致各向异性K_u和剩余磁化强度M_r⊥的单调下降.这可能是由于Cu原子在Pt层中的无序造成的，使Pt的晶面场对称性发生局域畸变，从而引起上述参数的下降.在特定区域内，可能是形成了PtCu合金的有序相，此时晶场对Co原子的作用就像只有Pt原子一样.这是Cu掺入 关键词：     

Magnetic properties of silicon doped with gadolinium

The magnetic semiconductor Gd_xSi_1-x was prepared by low-energy dual ion-beam epitaxy. Gd_xSi_1-x shows excellent magnetic properties at room temperature. A high magnetic moment of 10 _B per Gd atom is observed. The high atomic magnetic moment is interpreted as being a result of the RKKY mechanism. The indirect exchange interaction between ions is strong at large distances due to the low state density of the carriers in the magnetic semiconductor. PACS 81.05.Zx; 81.15.Hi; 75.50.Pp; 75.70.-i; 61.72.Tt     

Magnetic domain structures and magnetotransport properties in Co-Ag granular thin films

The magnetic microstructures and magnetotransport properties in granular Co_xAg_1-x films with 17%≤x≤62% were studied. Magnetic force microscopy (MFM) observations showed the presence of magnetic stripe domains in as-deposited samples with x≥45% and the evolution of the magnetic domain patterns to in-plane domains with annealing. A perpendicular magnetic anisotropy as high as about 8×10⁵ ergs/cc for as-deposited Co₆₂Ag₃₈ and about 6×10⁵ ergs/cc for as-deposited Co₄₅Ag₅₅ was observed by magnetization and torque measurements. With increasing annealing temperature, the perpendicular magnetic anisotropy became negative. The origin of the perpendicular magnetic anisotropy may be attributed to a rhombohedral distortion of the cubic cell due to residual substrate-film stresses. The magnetic stripe domains are the consequence of the interplay of the indirect or direct exchange, perpendicular magnetic anisotropy and dipolar interactions. Finally, magnetoresistance (MR) curves displayed training behaviours and different shapes when measured with different configurations (parallel, transverse and perpendicular). It is proposed that the existence and the evolution of the magnetic domain structures strongly affect the magnetotransport properties due to the extra contribution of the electron scattering at the domain walls. Furthermore, an anisotropic MR also contributes to the overall MR curves. Received: 2 March 2000 / Accepted: 28 March 2000 / Published online: 23 May 2001     

TiN和Ti1-xSixNy薄膜的微观结构分析

使用x射线衍射(XRD)、x射线光电子谱(XPS)、高分辨透射电子显微镜(HRTEM)和原子力显微镜（AFM）多种观测手段分析了TiN薄膜和Ti_1-xSi_xN_y纳米复合薄膜的微观结构.实验分析证明Ti_1-xSi_xN_y薄膜是由直径为3—5nm的纳米晶TiN和非晶Si₃N₄相构成，并且Ti_1-xSi_{x关键词： 纳米复合薄膜 自由能 表面粗糙度 TiN 1-x}Si_xN_y')" href="#">Ti_1-xSi_xN_y     

Observation of strain relaxation in Si1-xGex layers by optical and electrical characterisation of a Schottky junction

We have studied the effect of the strain relaxation on the band-edge alignments in a Pt/p-Si_1-xGe_x Schottky junction with x=0.14 by internal photoemission spectroscopy and current–voltage measurements. We have shown that the variations in the band-edge alignments can be observed directly by measuring the optical and electrical properties of a simple Schottky junction. The strain in the Si_1-xGe_x layer has been partially relaxed by thermal treatments at two different temperatures. The degree of relaxation and other structural changes have been determined by a high-resolution X-ray diffractometer. Both optical and electrical techniques have shown that the barrier height of the Pt/Si_0.86Ge_0.14 junction increases with the amount of relaxation in the Si_1-xGe_x layer. This shows that the valence-band edge of the Si_1-xGe_x layer moves away from the Fermi level of the Pt/Si_1-xGe_x junction. The band-edge movement results from the increase in the band gap of the Si_1-xGe_x layer after the strain relaxation. This result agrees with the theoretical predictions for the strain-induced effects on the Si_1-xGe_x band structure. Received: 18 October 2000 / Accepted: 19 December 2000 / Published online: 23 March 2001     

预注入对Si1-xCx合金形成的影响

室温下在单晶Si中注入(0.6—1.5)at%的C原子,部分样品在C离子注入之前在其中注入²⁹Si⁺离子产生损伤,然后在相同条件下利用高温退火固相外延了Si_1-xC_x合金,研究了预注入对Si_1-xC_x合金形成的影响.如果注入C离子的剂量小于引起Si非晶化的剂量,在950℃退火过程中注入产生的损伤缺陷容易与C原子结合形成缺陷团簇,难于形成Si_1-xC关键词： 离子注入 固相外延 1-xC_x合金')" href="#">Si_1-xC_x合金