无序晶态合金的电阻率

基于Baym原则,将Ziman型液态金属电阻理论推广到晶态金属及替代式的无序合金系统,给出了电阻率的一般表达式,讨论了它们的低温和高温行为。低温下用德拜晶格振动模型,无序晶态系统的电阻率可表为ρ=ρ₀+ρ_d(T/Θ)²+ρ_i(T/Θ)⁵,与实验一致。高温下,考虑到Debye-Waller因子及多声子效应,电阻率趋向饱和。用独立原子振动近似得到的简单公式与实验资料的比较表明:类似Nb这种电阻率的高温非线性偏离可以在本文的模型中自然地得到说明。     

Pentaquark Θ+的介质效应

在密度相关的相对论平均场理论基础上, 假定Θ⁺通过交换有效的同位旋标量介子σ和ω与其他重子发生相互作用, 研究了强子在包含Θ⁺的奇异核物质中的性质改变. 讨论并计算了介质中的Θ⁺和核子有效质量及其对重子密度的依赖关系, 分析了Θ⁺在核物质中包含的成分大小以及核子的同位旋效应对奇异核物质性质的影响, 进一步计算了不同重子组成比例下奇异核物质的标量密度ρ_S和矢量密度ρ_B的对应曲线.     

液晶N相→SA相相变点附近的反常声衰减

本文考虑在N→S_A相变中,当T→T_c⁺(相交点)时,声在液晶中传播引起的压力效应。使用模-模耦合方法计算了声的衰减和色散,得到在高频区间,声的衰减有反常发散行为,在低频极限声衰减的临界指数为2.5.当T→T_c⁺时,本文的理论曲线大体上与实验结果相一致。     

INFLUENCE OF IN-PLANE FIELD ON THE CRITICAL TEMPERATURE FOR THE BREAKDOWN OF VERTICAL BLOCH LINE CHAINS

The influence of in-plane field H_ip on the critical temperature T₀ for the breakdown of vertical Bloch line (VBL) chains of hard domains in garnet bubble films has been inves-tigated experimentally. It was found that T₀ can be significantly reduced by the increase of H_ip. Besides, the critical in-plane field H′_ip for the breakdown of VBL chains was measured as a function of temperature T for the same sample. As a result, the correlation between these two critical parameters, T₀ and H′_ip, was found. By introducing an effective in-plane field (H_ip)_e, the positive definiteness of the system of VBL pairs with two-dimemsional magnetization distribution was analyzed, giving rise to a theoretical expression of H′_ip(T): H′_ip(T) =|4πM_sQ(a₀+a₁Q +a₂Q²+a₃Q³+ a₄Q⁴)|^T_(T0(Hip=0)), where a_i are constants. It agrees well with the experiments.     

非晶Nd-Fe薄膜电阻的温度效应与非晶稳定性

用闪光蒸镀法在77K制备了Nd_xFe_1-x(x=0.06-0.80)非晶薄膜,原位测定了其电阻随温度的变化。结果表明:在0.192和ρ(T)∝T。晶化不是在一个固定的温度,而是在一个温度区间发生。     

深度非弹性散射中的大快度间隔事件与雷吉子

分析了HERA实验上ep电荷交换过程的最大赝快度分布的实验结果.利用雷吉唯象理论计算了在这个过程中R_ρ(位于ρ⁺轨迹的雷吉子)交换的贡献.并用π介了云模型计算了同一过程中π⁺交换的贡献.运用Monte Carlo方法模拟了来态粒子的最大赝快度分布.结果表明,单独考虑哪一种交换过程都不能很好地解释实验结果,而当同时计入两者的贡献时,理论预言与实验数据符合较好.     

立方晶体铁磁各向异性的自旋波理论

本文研究了金属极性模型理论中立方铁磁体的d电子之间各向异性相互作用的可能形式,并根据Dyson的自旋波相互作用理论用统计微扰论的方法计算了它们对磁各向异性常数K₁(T)的贡献。计算进行到T⁴的项,在计算中保留到各向异性作用常数的一次方。所得到的K₁(T)的温度依赖关系,在理论适用的温度范围内,基本上正比于自发磁化强度的10次方。     

化学计量的氧化钠团簇阳离子结构的离子迁移质谱法研究

本文通过离子迁移质谱法研究了氧化钠团簇阳离子(Na_nO_m⁺,n≤11)的稳定结构. 质谱结果表明化学计量组成Na(Na₂O)_(n-1)/2⁺ (n=3、5、7、9和11)系列是稳定的,并且NaO(Na₂O)_(n-1)/2⁺ (n=5、7、9和11)系列作为二级稳定系列. 为了获得这些团簇离子的结构,通过离子迁移率测量实验测定离子和氦缓冲气体之间的碰撞截面. 同时计算了这些组合物优化结构的理论碰撞截面. 结果表明,Na(Na₂O)_(n-1)/2⁺和NaO(Na₂O)_(n-1)/2⁺的结构除了n=9之外,其它具有相似结构框架. Na(Na₂O)_(n-1)/2⁺所有的化合键位于钠和氧之间. 另一方面,NaO(Na₂O)_(n-1)/2⁺中除了Na-O键之外,还存在一个O-O氧键,表明NaO(Na₂O)_(n-1)/2⁺具有过氧化物离子(O₂^2-)作为Na(Na₂O)_(n-1)/2⁺的氧化物离子(O^2-) 的替代物. Na(Na₂O)_(n-1)/2⁺和NaO(Na₂O)_(n-1)/2⁺两种稳定系列都是闭壳组合物. 这些闭壳特征对氧化钠簇阳离子的稳定性具有强烈影响.     

18 MeV质子辐照对TiNi形状记忆合金R相变的影响

 研究了用HZ-B串列加速器的18MeV质子辐照对TiNi形状记忆合金R相变的影响，辐照在奥氏体母相状态下进行。示差扫描量热法（DSC）表明，辐照后R相变开始温度T^s_R和逆马氏体相变结束温度T^f_A随辐照注量的增加而降低。当注量为1.53×10¹⁴/cm²时，T^sR和T^f_A分别下降6K和13K，辐照未引起R相变结束温度T^s_R和逆马氏体相变开始温度T^f_A的变化。表明辐照后母相(奥氏体相)稳定。透射电镜（TEM）分析表明辐照后没有引起合金可观察的微观组织变化。辐照对R相变开始温度T^s_{R和逆马氏体相变结束温度Af的影响可能是由于质子辐照后产生了孤立的缺陷团，形成了局部应力场，引起晶格有序度的下降所造成的。}     

超导临界温度理论(Ⅰ)

本文求出了Eliashberg方程在T=T_c时的解,得到了下面的临界温度级数表示式:T_c=α₀(μ^*)(λ〈ω²〉)^1/2{1+1/λα₁(μ^*)〈ω⁴>/〈ω²>²+1/λ²(α₂₁(μ^*)〈ω⁶>/〈ω²>³+α₂₂(μ^*)〈ω⁴>²/〈ω²>⁴) +1/λ³(α₃₁(μ^*)〈ω⁸>/〈ω²>⁴+α₃₂(μ^*)(〈ω⁴>〈ω⁶>)/〈ω²>⁵)+α₃₃(μ^*)〈ω⁴>³/〈ω²>⁶+…},其中α₀(μ^*),α₁(μ^*)等仅是μ^*的函数。新的T_c公式表明了,T_c不仅依赖于λ、μ^*和〈ω²〉,而且依赖于有效声子谱α²F(ω)的各级矩〈ω²ⁿ〉。     

Experimental study of resistivity of metallic materials with dynamic disorder

As a result of strong electron-phonon interaction, the enhancement of scattering with increasing temperature may decrease the mean free pathl in crystals down to interatomic distances:l≈a. This means that with respect to the electron wave the degree of the atomic disorder in these crystals is approximately the same as in amorphous metal. Because of a high electron velocity the dynamic character of the disorder seems to be unimportant. At the same time, the degree of disorder can be easily changed by varying the temperature. This makes it possible to simulate and study the transport properties of the disordered media on highquality crystals with strong phonon scattering. The sign that indicates the fitness of a crystalline metallic material for such studies is the saturation of its resistivityρ that ceases to grow as the temperature is increased. The saturation of resistivity was investigated experimentally on (i) Cu-Zr alloys in the crystalline state, (ii) single crystals of WO₂, which is a metal with well-defined Fermi surface. The samples of Cu-Zr were produced by the recrystallization of amorphous ribbon. Some of these samples reveal resistivity saturation. With further increase ofT a maximum in theρ(T) dependence was observed at those compositions which slightly decreased theirρ value under recrystallization. This unusual dependence can be explained in terms of the two-band model assuming that thed-electrons reach the minimal free path,l≈a, while thes-electrons do not. The WO₂ crystals were used to study the anisotropy of (T). In the directions, whereρ is high, there is a tendency to saturation. Whereρ is low, no tendency to saturation is observed. The quantitative analysis of the curves has shown that not only the absolute value but also the relative value of the deviation from the Boltzmann lawρ～T decreases down as the resistivity decreases.     

Transport properties and magnetoresistance in CoNb1−xMnxSb half-Heusler alloys with a low temperature localization

The transport properties and magnetoresistance of half-Heusler CoNb_1−xMn_xSb (x=0.0-1.0) alloys have been investigated between 2 and 300 K. In this temperature range, a metallic conductivity has been observed for the alloys with higher (x=1.0) and lower (x=0.0-0.2) Mn contents. However, the middle Mn content alloys (x=0.4-0.8) exhibit non-metallic conductive behavior. Their temperature dependence of resistivity undergoes a Mott localization law ρ=ρ₀exp(T₀/T)^p (p=1/4) rather than a thermal excitation regime ρ=ρ₀exp(E_a/kT) at low temperature (). The localization can be attributed to atomic and magnetic disorder. Resistivity peaks from 25 to 300 K were also observed for these alloys. Magnetotransport investigation reveals that these resistivity peaks result from localization effect as well as spin-disorder scattering.     

非晶态Fe87-xSixB13合金的磁化强度、电阻与温度的关系

本文研究了非晶态Fe_87-xSi_xB₁₃(x=0,9.6,14.5)合金的饱和磁化强度、电阻率与温度的关系。得到样品的居里温度T_C和晶化温度T_cr随Si含量的增加而明显提高。低温下的热磁关系符合布洛赫的T^3/2定律,计算出自旋波劲度系数D从x=0时的62meV·A²增加到x=14.5时的111meV·A²。从D值和Handrich理 关键词：     

不同氧含量Bi2Sr2CaCu2O８+δ单晶电阻率的各向异性

精确测量了在不同氧压下退火的单晶Bi₂Sr₂CaCu₂O_8+δ(Bi2212)样品的Cu-O面内和Cu-O面外的电阻率ρ_c(T)和ρ_ab(T).发现ρ_c(T)和各向异性比(ρ_c(T)/ρ_ab(T))随着载流子浓度增加而迅速下降.在过掺杂样品中,高于120K时,ρ_c随温度线性下降,而各向异性 关键词：     

Cu3Au的电阻率和长程有序

基于作者最近发展的晶态合金电阻理论,本文对Cu₃Au电阻率的温度系数随长程有序度增加而增大的现象给出一个解释,用一个简单的模型赝势计算Cu₃Au的ρT及(dρT/dT),所得结果与实验资料一致。 关键词：     

Tunneling thermopower in magnetic granular alloys

The nature of the field dependence of thermopower in the Co-Al-O and Fe-Al-O magnetic granular alloys with tunneling conduction is shown to be related to tunneling thermopower. The tunneling thermopower is small and depends approximately linearly on temperature and squared magnetization, and its field dependence is described by a relation of the type S(H)/T=a+bρ(0)/ρ(H), where ρ is the alloy electrical resistivity and the parameters a and b are field-independent.     

Au1-xNix合金(x=0.30-0.42)低温电阻率极小值的机理探讨

为了解释Au_1-xNi_x合金(x=0.30—0.42)低温出现电阻率极小值的实验结果,本文提出一个低浓度自旋集团顺磁态合金的模型,得到自旋集团孤立近似下和自旋集团耦合作用下的电阻率公式,并和晶格散射的贡献(由Au₈₀Ni₂₀合金或Au-Cu合金的ρ_i(T)实验数据代替)联合起来,得到ρ(T)的计算曲线,和实验结果符合得很好。当Tmin,电阻率随温度增高而下降,主要是自旋集团孤立近似下的Kondo效应引起的。自旋集团之间的RKKY耦合作用对电阻率的贡献在低温时大,随着温度增高按1/T规律迅速减小,所以ρ(T)-ρ_i(T)实验值在相当宽温度范围出现logT关系。随着温度增高,晶格散射对电阻率的贡献将变得重要,当T=T_min,电阻率出现极小值。 关键词：     

Effective medium theory for the inhomogeneous PdMnxFe1−x alloys

Ternary PdMn_xFe_1−x alloys are known to form a microinhomogeneous random mixture of PdMn and PdFe phases. The unconventional ρ(x) dependence of dc resistivity and singularities in low frequency optical conductivity spectra of alloys are described footing within the effective medium approach. The essential point of the model proposed is the anomalous role of insulating interfaces, whose proliferation at intermediate x gives rise to the observed maximum of resistivity near x?0.8.