Electrical resistivity of amorphous Zr70Cu30 and the Kondo like model

Electrical resistivity measurements of amorphous Zr₇₀Cu₃₀ as a function of the concentrations of two level systems show that a Kondo like theory cannot explain the observed temperature dependence.     

Critical temperature and density of states in amorphous Zr70Cu30

By means of thermal heat treatment of amorphous Zr₇₀Cu₃₀ it is shown that the induced decrease in critical temperature is followed by a reduction in the electronic density of states of the same magnitude as that obtained by changing the Cu concentration. This result indicates that the density of states is the fundamental microscopic parameter determining the superconducting behavior.     

Surface normal regions in superconducting Zr70Cu30 induced by thermal relaxation

Penetration depth measurements show that thermal heat treatment in amorphous Zr₇₀Cu₃₀ induces a normal region 5000 Å thick at the surface of ultrarapid quenched ribbons. Upper critical field measurements indicate that the new induced phase is a normal one while the rest of the sample remains as a homogeneous superconducting phase.     

Effects of nickel on the crystallization of Zr70Cu20Ni10 amorphous alloy

Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) are employed to investigate the effects of nickel on the crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy. We have found that the crystallization process of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy is strongly influenced by the addition of nickel. Addition of 10 at% Ni to the Zr₇₀Cu₃₀ amorphous alloy makes the crystallization process proceed from a single-stage mode to a double-stage mode. The activation energy for crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy is calculated to be about 388kJ·mol^-1 on the basis of the Kissinger equation. The effects of nickel on the crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy are discussed in terms of the genetics of metals.     

Superconducting behavior of amorphous Zr70Cu30

Measurement of the Meissner penetration depth, λ(T) were made in amorphous Zr₇₀Cu₃₀ samples. The results indicate that this amorphous alloy behaves as a BCS superconductor with 2Δ(0)?kT_c = 3.8, where Δ(0) is the superconducting energy gap at T=0 and T_c the critical temperature. It is also concluded that the low energy excitation, TLS, characteristics of amorphous material does not contribute to T_c.     

Model relating superconductive penetration depth and metallurgical phase separation in amorphous La70Cu30

A model is proposed to account for the large increase in the measured penetration depth of superconducting, amorphous La₇₀Cu₃₀ when the specimens are annealed sufficiently long near, but below, the crystallization temperature. It is suggested that a metallurgical phase separation occurs with domain dimensions in the submicrometer range. Penetration depth measurements as a function of temperature in a weak magnetic field are a useful tool to detect changes in phase separation in high-K materials.     

Superconducting properties of amorphous sputtered Zr70Mo30

Specific heat, resistivity and critical superconducting fields (H_c and H_c2) measurements show that amorphous Zr₇₀Mo₃₀ is an intermediate superconductor (T_c = 4.3 K; λ = 0.77). The coupling strength is mainly governed by the electronic properties. Like in the Zr?3d alloys previously investigated, a discrepancy between the measured and calculated upper critical field slope is reported. The effect of two-level systems (TLS) needs to be clarified.     

退火态Zr55Al10Ni5Cu30块体非晶合金在轧制过程中的自由体积演化

将Zr₅₅Al₁₀Ni₅Cu₃₀块体非晶合金在715 K等温退火30 min, 引入少量纳米晶, 然后于室温以不同的应变速率进行轧制, 用差示扫描量热仪考察不同应变量样品的热稳定性和自由体积演化. 结果表明:即使轧制到95%的最大应变量, 样品的热稳定性也几乎没有发生改变. 在各种应变速率下, 随着应变量的增加, 自由体积含量持续上升. 但随着应变速率的增加, 相同应变量下自由体积的含量先上升后降低, 该规律与单一非晶态结构合金在塑性变形过程中自由体积的变化情况截然不同.     

块体金属玻璃Zr46.75Ti8.25Cu7.5Ni10Be27.5的超导与负电阻温度系数

测量了块体金属玻璃Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5在退火前后其电阻值随温度的变化,测量的温度范围为1.5—300K.样品在退火前后都发现有超导现象.零磁场下其超导转变温度T_c分别为1.84和3.76K.在5—300K温度范围内,原始样品具有负的电阻温度系数.如果取Zr, Ti, Cu, Ni及Be分别贡献出1.5, 1.5, 0.5, 0.5及两个传导 关键词： 块体金属玻璃 超导 电阻温度系数     

Electron transport properties of amorphous Mg80.4Cu19.6 alloy

The Hall coefficient, thermoelectric power and electrical resistivity of the liquid quenched amorphous Mg_80.4Cu_19.6 alloy have been measured over a wide temperature range below room temperature. The 2k_F value deduced from the observed Hall coefficient agrees well with the free electron value. The thermoelectric power is positive and increases linearly with increasing temperature above approximately 180 K. The downward deviation is evident in the lower temperature range. This behaviour is in sharp contrast with the negative thermoelectric power observed in the amorphous Mg-Zn alloy. Nevertheless, the overall temperature variation of the electrical resistivity resembles the previously reported data of the amorphous Mg_72.5Zn_27.5 alloy in various aspects; (1) the room temperature resistivity value, (2) the negative TCR and its magnitude, (3) the appearance of a broad maximum at about 50 K and a minimum at about 10 K and (4) T²-dependence in the range of 10～30 K and $\text{-(T-T}{}_{\max }\text{)}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$-dependence in the range of 50～220 K. The results are discussed in connection with $\text{2k}{}_{\mathrm{F}}\text{K}{}_{\mathrm{P}}$ criterion and Mooij correlation.     

Phonon scattering by electrons and low energy excitations in a metallic glass

Measurements of the thermal conductivity of a superconducting metallic glass Zr₇₀Cu₃₀ in zero field and in a magnetic field exceeding the upper critical field allow a quantitative determination of the strength of the phonon-electron scattering for the first time in amorphous metals. The temperature dependence of the residual phonon scattering by localized low energy excitations is similar to that found in insulating glasses.     

On the structure of amorphous sputtered Zr76Cu24 alloy

X-ray diffraction experiments have been performed on amorphous sputtered Zr₇₆Cu₂₄ alloy in order to investigate the structural relaxation induced by thermal annealing below the crystallization temperature. Contrary to the low-temperature thermal properties which are very sensitive to heat treatments, only weak modifications affect the short-range structural order as defined by the total radial distribution function.     

非晶态Cu56Zr44合金的结构及其等温退火晶化过程的研究

利用X射线衍射技术、差示扫描量热分析技术和透射电子显微镜研究了非晶态Cu₅₆Zr₄₄合金的结构及其等温退火条件下的晶化过程.实验结果表明,非晶态Cu₅₆Zr₄₄合金在室温下的短程结构类似于硬球无规密堆积分布.在703K过冷液相区内等温退火时发现,当退火时间为3min时,晶化产物主要为Cu₈Zr₃相;当退火时间为6min时,Cu₈Zr₃关键词： 非晶态 56Zr₄₄合金')" href="#">Cu₅₆Zr₄₄合金 结构 等温退火     

Cu60Zr30Ti10非晶合金弛豫和晶化过程的小角X射线散射研究

应用小角X射线散射技术研究了Cu₆₀Zr₃₀Ti₁₀非晶合金从300到813 K之间微结构的演化情况.发现在淬火状态下Cu₆₀Zr₃₀Ti₁₀非晶合金中存在直径30 nm左右的富Cu区.非晶的结构弛豫包括573 K之前的低温结构弛豫和573 K到玻璃转变温度的高温结构弛豫，弛豫的结果是产生含有有序原子团簇的富Cu区，这些有序原子团簇的富Cu区是随后晶化过程中晶核产生的基础.Porod曲线分析表明，晶化生成的纳米体心立方CuZr相和基体之间有明锐的界面. 关键词： 小角X射线散射 非晶合金 结构弛豫 晶化     

High critical magnetic field superconductor La3S4

We report electrical conductivity, specific heat and magnetization measurements on La₃S₄ single crystals. The results show, that La₃S₄ is a strong coupling superconductor with a BCS coherence length of 132 Å. This extremely low value makes La₃S₄ an intrinsic high critical magnetic field superconductor with a Landau-Ginsburg parameter κ₀ of 20. For the temperature gradient of the upper critical magnetic field at the transition temperature we find values up to 35 kG/K.     

The electrical resistivity of amorphous alloys at low temperatures

Measurements of the temperature- and magnetic field dependence of the electrical resistance of some metallic glasses are presented. The data obtained for Cu₅₇Zr₄₃, Cu₄₀Zr₆₀ and Pd₃₀Zr₇₀ demonstrate that deviations from the high temperature behaviour extrapolated to low temperatures are caused by superconducting effects. The paraconductivity which is strongly enhanced in amorphous alloys is shown to agree quite well with theoretical models. The normal state resistance does not saturate down to temperatures of about 2 K. It still exhibits a negative temperature coefficient of the resistivity.     

Acoustic experiments on amorphous Pd30Zr70 and Cu30Zr70 in the superconducting and the normal state

Measurements of internal friction and sound velocity of amorphous Pd₃₀Zr₇₀ and Cu₃₀Zr₇₀ around 1 kHz and of Pd₃₀Zr₇₀ around 1 GHz are presented for both the superconducting and the normal state. Our experiments reveal several serious discrepancics with the predictions of the Tunneling Model and its extension to metallic glasses. Particularly from internal friction we conclude that the density of states of the tunneling systems is affected by the presence of conduction electrons. We discuss our results on the basis of recent theories which consider a slowing down of the tunneling motion due to the interaction with conduction electrons.Dedicated to K. Dransfeld on the occasion of his 60th birthday     

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：     

A simulation study of rapid solidification and crystal configuration of Cu70Ni30 alloy

A molecular dynamics (MD) simulation study has been performed for the rapid solidification of Cu₇₀Ni₃₀ adopting the quantum Sutton-Chen many-body potentials. By analyzing the bond-types and the relation of atomic average energy versus temperature, it was demonstrated that as cooling rate being 2×10¹² K/s, the Cu₇₀Ni₃₀ formed fcc crystal structures and freezing point was found. In addition, having analyzed the transformation of microstructures and the detail of crystal growth by using atomic trace and visual method, not only could the formation of binary disordered solid solution be showed, but also the solidification of liquid metals and the crystal growth processes could be, further understood.     

A STUDY OF THE CRYSTALLIZATION OF AMORPHOUS Cu60Zr40 ALLOY

The crystallization of the amorphous Cu₆₀Zr₄₀ alloy has been studied by differential scanning calorimetry (DSC), scanning Auger microprobe (SAM) and transmission electron microscopy (TEM). The DSC trace showed that the sample exhibited a glass transition at 750 K and a strong exothermic effect beginning from 782 K. An enrichment of the element Zr and significant oxygen contamination in a zone near the surface to a depth of about 10 nm were revealed by SAM in the analysis of surface competition and depth profiles of the Cu₆₀Zr₄₀ sample. Also, the change of concentration ratio of Ca to Zr in amorphous matrix at the clean Cu₆₀Zr₄₀ surface as a function of annealing temperature was examined in detail, and it was found that the concentration of Zr at the surface is slightly higher than that in the bulk until 780K and that the concentration ratio of Cu to Zr in matrix has an abrupt increase in the temperature range of 780-800K. The observations by high resolution TEM revealed the appearance of cluster-like regions of approximately 1.5-2.0 nm in size just before crystallization and they distributed randomly throughout the sample. This phenomenon is analogous to the results obtained using field ion microscopy (FIM) by the present authors. The microstructural changes of the sample daring heating show the gradual crystallization of the amorphous matrix.