金属玻璃(Cu_(1-x)Ni_x)_33Zr_(67)合金的低温电阻率

本文研究了金属玻璃(Cu_(1-x)Ni_x)_(33)Zr_(67)合金的低温电阻输运特性。在较宽的温区(2—273K)测试了电阻率,测量结果符合Mooij判据。样品电阻率随温度的变化行为与双能级隧道模型符合较好。     

重电子金属CeCu(6-x)Nix低温电阻与比热的研究

测量了重电子金属CeCu6-xNix(x=0,005,01,015,02)01K—250K的低温电阻和5K—70K低温比热,发现样品电阻的极大值温度随着掺Ni含量的增大而急剧下降,这一现象反映少数与Ni邻近的Ce离子在极低温下磁矩的加强和整个Ce离子点阵对导电电子相干散射的减弱.与此相反,低温电子比热系数γ在较低温度下近于常数,而在8K附近因有效质量变大而明显上升,但γ明显上升的温度,对Ni的含量却不敏感,表明绝大部分Ce离子的状况并未受到影响 关键词： 重费米子系统 低温比热 低温电阻     

炭电阻低温温度计(Ⅳ)

本文报道了炭电阻低温温度计批量性元件低温性能实验结果:低温稳定性、低温复现性、电阻-温度关系式等.并给出0—5.4T,小于4.2K 和0—10T、4.2K 的磁致电阻曲线.     

(Fe_(0.1)Co_(0.55)Ni_(0.35)_(78)Si_8B_(14)金属玻璃的晶化过程及压力的影响(Ⅱ)——晶化温度和晶化激活能

本文用高压下原位电阻测量法研究了3GPa以下(Fe_(0.1)Co_(0.55)Ni_(0.35))_(78)Si_8B_(14)金属玻璃的晶化温度T_x,并用Kissinger法求得不同压力下金属玻璃的晶化激活能△E_x。测量结果表明,施加压力时这种合金的T_x并不是单调地、更不是线性地升高的,而是在上升的总趋势中还存在某些局部的转折。这和一些被广泛引用的结论是不同的。晶化激活能△E_x也随压力作类似趋势的变化。分析认为,压力促进晶化时的成核过程,而抑制晶核的扩散性长大。两者的综合作用是造成△E_x、从而也构成T_x非单调变化的原因。压力除了通过△E_x影响T_x以外,指数前因子的压力效应也可以使晶化温度产生重要的改变。     

金属玻璃(Cu1-xNix)33Zr67合金的低温电阻率

本文研究了金属玻璃(Cu_1-xNi_x)₃₃Zr₆₇合金的低温电阻输运特性。在较宽的温区(2—273K)测试了电阻率,测量结果符合Mooij判据。样品电阻率随温度的变化行为与双能级隧道模型符合较好。 关键词：     

近藤(Kondo)效应介绍

在稀磁合金中,由于杂质与传导电子的交换作用,使这类系统的低温电子特性表现出一系列的反常.最早观测到的是在电阻随温度变化的曲线上出现极小;其次是磁化率偏离居里定律,有效磁矩随温度降低连续减小,以及比热和热功率在低温下出现宽峰等一系列反常现象.日本物理学家近藤(J.Kondo)首先对电阻极小现象作出了正确的理论解释,并提出了深入研究的基本问题,大大活跃了这一研究领域,从此人们将稀磁合金中低温反常现象的研究通称为Kondo效应. 一、电阻极小现象 早在1930年Meissner和Voight[1]就观测到金(Au)的电阻温度曲线在10K附近出现了一个浅…     

氧缺陷导致的结构无序对La_(2/3)Sr_(1/3)MnO_3薄膜电输运特性的影响(英文)

为了澄清结构无序对电输运特性,特别是低温下电阻极小的影响,采用脉冲激光沉积方法在LaAlO3(100)基片上制备了两类La2/3Sr1/3MnO3薄膜.一块是在通40Pa氧气的气氛下沉积,沉积后不再进行通氧气的原位退火.另一块在同样通40Pa氧气的气氛下沉积,但沉积后再在6×104Pa的氧气气氛下进行原位退火.对两种薄膜的结构,磁特性和电输运特性进行了对比研究.结果表明:氧缺陷导致了薄膜结构的无序,更导致了类似自旋玻璃行为的磁无序.电输运特性结果表明原位退火使得薄膜的金属-绝缘体转变温度Tc从约195K提高到335K.对由于结构无序的存在对低温电阻较小行为的影响作了系统对比研究,曲线拟合的结果表明对于缺氧薄膜和进行了原位退火的薄膜的低温电阻较小行为的主要影响因素分别是类近藤散射作用和电子-电子相互作用,这一结果对于澄清庞磁电阻锰氧化物体系的低温电阻极小现象有一定积极意义.     

重电子金属CeCu5.8 M0.2(M=Ni,Zn,Cd) 低温物性的比较

研究了不同元素等量掺杂下重电子金属CeCu5.8M0.2(M=Ni,Zn,Cd)低温电阻、比热容和磁化率随温度的变化关系.分析讨论了掺杂元素M(M=Ni,Zn,Cd)的磁性、价态及原子尺寸对近藤温度Tk、相干温度(即电阻极大值的温度TRmax)、每个Ce离子在较高温度时的平均磁矩μB以及在温度降低时被传导电子自旋屏蔽过程的影响.     

由观测无胁强作用下的热膨胀和电阻研究金属玻璃(Fe_(0.85)Ni_(0.15))_(84)B_(16)的结构弛豫

本文通过长度、电阻和热膨胀系数的测量研究了(Fe_(0.85)Ni_(0.15))_(84)B_(1c)金属玻璃结构弛豫和退火温度T_a的关系。基于上述物理量对结构弛豫的关系,对曲线作了分析和讨论。在退火温度为175℃至250℃之间结构弛豫随T_a的变化率最大。     

Mo低掺杂La_(0.67)Sr_(0.33)MnO_3的磁电特性及室温磁电阻增强(英文)

采用固相反应法成功制备了Mo低掺杂La0.67Sr0.33Mn1-xMoxOc(x=0,0.02)单相多晶样品,系统研究了样品的磁性、电输运特性和磁电阻效应.发现Mo低掺杂对La0.67Sr0.33MnO3 的居里温度影响很小,但在La0.67Sr0.33MnO3铁磁基态背景下诱导出团簇自旋玻璃态行为.在低温区(0.1相似文献   

AC impedance analysis of LaLiMo2O8 electroceramics

Complex impedance analysis of a new rare earth-based ceramic oxide, LaLiMo₂O₈, prepared by a standard solid-state reaction technique has been carried out. Material formation under the reported conditions has been confirmed by X- ray diffraction studies. A preliminary structural analysis indicates the crystal structure to be orthorhombic. Electrical properties of the material sample have been studied using AC impedance spectroscopy technique. Impedance spectrum results indicate that the electrical properties of the material are strongly dependent on temperature and it bears a good correlation with the sample microstructure (i.e. the presence of bulk, grain boundary, etc.) in different temperature ranges. Evidences of temperature-dependent electrical relaxation phenomena in the material have also been observed. The bulk resistance, evaluated from complex impedance spectrum has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance (NTCR)-type behavior like that of semiconductors. The DC conductivity shows typical Arrhenius behavior when observed as a function of temperature. The AC conductivity spectrum has provided typical signature of an ionically conducting system and is found to obey Jonscher's universal power law. Modulus analysis has indicated the possibility of hopping mechanism for electrical transport processes in the system with non-exponential-type conductivity relaxation.     

PZT-8型铁电压电陶瓷的低频介电特性

本文研究PZT-8型多晶锆钛酸铅铁电压电陶瓷,通过介电温度、频率响应谱的研究,对它的损耗机制、弛豫过程、杂质影响等作了讨论,认为,高温时主要是电导损耗起作用,并对如何改进PZT-8型铁电陶瓷的电学性能,提出了相应的设想。 关键词：     

低温下单根ZnO纳米带电学性质的研究

用化学气相沉积法在硅衬底上合成了宽1 μm左右、长数十微米的ZnO纳米带. 采用微栅模板法得到单根ZnO纳米带半导体器件, 由I-V特性曲线测得室温下ZnO纳米带电阻约3 MΩ, 电阻率约0.4 Ω·cm. 研究了在20–280 K温度范围内单根ZnO纳米带电阻随温度的变化. 结果表明: 在不同温度区间内电阻随温度变化趋势明显不同, 存在两种不同的输运机制. 在130–280 K较高的温度范围内, 单根ZnO纳米带电子输运机制符合热激活输运机制, 随着温度继续降低(< 130 K), 近邻跳跃传导为主导输运机制. 关键词： ZnO 纳米带 低温 输运机制     

Structural and impedance properties of Ca3Nb2O8 ceramics

Polycrystalline sample of Ca₃Nb₂O₈ was prepared by a high-temperature solid-state reaction technique. X-ray diffraction (XRD) analysis confirms the formation of single-phase compound of hexagonal (rhombohedral) crystal structure at room temperature. Scanning electron micrograph of the material showed uniform grain distribution on the surface of the sample. Detailed studies of dielectric properties of the compound, studied in a wide frequency range (10²-10⁶ Hz) at different temperatures (25-500 °C), exhibit a dielectric anomaly suggesting phase transition of ferroelectric-paraelectric and structural type at 300 °C. Electrical properties of the material were analyzed using a complex impedance technique. The Nyquists plot showed the presence of bulk effect in the material in the studied temperature range. Studies of electrical conductivity over a wide temperature range suggest that the compound has negative temperature coefficient of resistance behavior.     

Electrical properties and dielectric relaxation of thermally evaporated zinc phthalocyanine thin films

The electrical transport properties and dielectric relaxation of Au/zinc phthalocyanine, ZnPC/Au devices have been investigated. The DC thermal activation energy at temperature region 400-500 K is 0.78 eV. The dominant conduction mechanisms in the device are ohmic conduction below 1 V and space charge limited conduction dominated by exponential trap distribution in potentials >1 V. Some parameters, such as concentration of thermally generated holes in valence band, the trap concentration per unit energy range at the valence band edge, the total concentration of traps and the temperature parameter characterizing the exponential trap distribution and their relation with temperatures have been determined. The AC electrical conductivity, σ_ac, as a function of temperature and frequency has been investigated. It showed a frequency and temperature dependence of AC conductivity for films in the temperature range 300-400 K. The films conductivity in the temperature range 400-435 K increased with increasing temperature and it shows no response for frequency change. The dominant conduction mechanism is the correlated barrier hopping. The temperature and frequency dependence of real and imaginary dielectric constants and loss tangent were investigated.     

Spin glass behaviour and magnetic anisotropy in DyFe4Al8 single crystals

Measurements of electrical resistivity, AC and DC magnetic susceptibilities of a DyFe₄Al₈ single crystal were performed in the temperature range 4.2–300K. A thermomagnetic effect was found below 30K. The strong anisotropy of the magnetic susceptibility occurs in the whole temperature range and is very pronounced at low temperatures. A T²-dependence of the electrical resistivity in the temperature range 4.2–100K and an antiferromagnetic transition at 185K were found. A cusp in the AC susceptibility was observed below 100K with a maximum at 30K.     

Monolithic Uncooled 8 × 8 Bolometer Arrays Based on Poly-SiGe Thermistor

This paper presents a monolithic uncooled 8 × 8 bolometer array with polycrystalline silicon-germanium (poly-SiGe) thermistors as active elements. The poly-SiGe films are deposited by ultrahigh vacuum vapor deposition (UHV/CVD) system and the dependence of the temperature coefficient of resistance (TCR) on annealing temperature has been investigated. To decrease the thermal conductance of the bolometer, the poly-SiGe thermistor was formed on a four leg suspended microbridge. The improved porous silicon micromachining techniques described here enable the integration of the bolometer array with the MOS readout circuitry. The measurements and calculations show that the mean responsivity is 1.07 × 10⁴ V/W with an uncorrected uniformity of 10.5% and a thermal response time of 10.5 ms, and the detectivity of 3.75 × 10⁸ cm Hz^1/2/W is achieved at a chopping frequency of 30 Hz and a bias voltage of 5 V.     

In situ electrical resistance and activation energy of solid C_(60) under high pressure

The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300-423 K by using a designed diamond anvil cell. In the experiment, four parts of boron-doped diamond films fabricated on one anvil were used as electrical measurement probes and a W-Ta thin film thermocouple which was integrated on the other diamond anvil was used to measure the temperature. The current results indicate that the measured high-pressure resistances are bigger than those reported before at the same pressure and there is no pressure-independent resistance increase before 8 GPa. From the temperature dependence of the resistivity, the C60 behaviors as a semiconductor and the activation energies of the cubic C60 fullerene are 0.49, 0.43, and 0.36 eV at 13, 15, and 19 GPa, respectively.     

Preparation and characterization of molybdenum diselenide thin films

MoSe₂ layers, synthesized by annealing a molybdenum foil under selenium pressure, have been investigated by scanning electron microscopy, X-ray analysis, electron spectroscopy (XPS) and electrical resistance measurements. It has been found that stoichiometric layers are obtained after appropriate processing. The films crystallize in the hexagonal structure. The crystallites develop preferentially along the c axis. The binding energies deduced from the XPS lines were found to be in good agreement with those of the reference powder. The electrical resistance is governed by hopping conduction in the low temperature range (80–250 K) and by grain boundary scattering mechanisms at higher temperatures.     

Effect of mechanical tension on electrical transport properties of amorphous Fe92Zr8 alloy

The effect of mechanical tension and magnetic field on the electrical resistivity of amorphous Fe₉₂Zr₈ alloy has been studied as a function of temperature. The results show that resistivity is enhanced by the applied tension and magnetic field. The increase in the electrical resistivity is attributed to volumetric effect, disorder scattering and thermal vibrations. The observed increase in the Curie temperature caused by the applied stress was found to be about 7×10^–6 °C/PA and indicates that some structural changes occurred.