高Tc超导体的表面微波吸收

测量不同粒度及低真空条件下高T_c超导样品Bi-Pb-Sb-Sr-Ca-Cu-O的非共振微波吸收信号,实验表明,这个对温度和磁场十分敏感的信号还与样品颗粒的大小及氧气氛有关;并经计算证明,信号强度与近表面趋肤深度壳层Meissner态的体积成正比。 关键词：     

Bi系超导体高Tc相的形成机制

本文研究Bi系超导体高T_c(2223)相的形成机制。提出Bi系氧化物超导体高T_c相的形成过程是:首先Sr-Ca-Cu氧化物(Ca_0.85Sr_0.15CuO₂)与低T_c(2212)相反应形成高T_c相的核,然后样品内2223相核通过象结晶学中晶体生长那样的方式长大成2223相晶粒。2223相成核过程中Sr-Ca-Cu氧化物的形成途径有两条:一条是通过固相反应 关键词：     

高Tc氧化物超导体Bi(Pb)-Sr-Ca-Cu-O(F)的“不可逆线”

研究了高T_c氧化物超导体Bi(Pb)-Sr-Ca-Cu-O(F)体系的“不可逆线”。发现不可逆磁场H^*<120Oe时,H^*=1590(1—t)^3/2;当120Oe*<1000Oe时,H^*=35700(1—t)^3/2-2480。指出H^*(T)曲线是一个磁通格子熔化线,在曲线以下属于磁通蠕动区;在H^*(T)与H_c2(T)之间属于磁通格子液态区,即磁通流动区。 关键词：     

(BiPb)-Sr-Ca-Cu-O2223相高Tc超导体磁通钉扎与蠕动

本文介绍了(BiPb)-Sr-Ca-Cu-O2223相高T_c超导体烧结工艺,用振动样品磁强计测量了磁化强度地豫率随外磁场的变化,并相应求得钉扎势U₀随外磁场的依赖关系。发现在0—0.23T外磁场范围内U₀与外磁场B的关系为U₀-B^-1/2与Palstra对单晶用电阻展宽实验所得结果有类似的函数形式。 关键词：     

新型1223相高Tc超导层型铜氧化物(Tl,M)(Sr,Ba)2Ca2Cu3Oz(M=Cr,V)

纯的TlSrCaCuO体系难以制备1223型超导铜氧化物,报道了合成和用粉末X射线衍射、电子衍射鉴定了一大类新型1223相高T_c超导层型铜氧化物(Tl_(1_x)M_s)(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,其中M为Cr或V,包括(Tl_(0.75)Cr_(0.25)(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,(Tl_(0.75)V_(0.25))(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,(Tl_(1_x)Cr_x)Sr_2Ca_2Cu_3O_x和(Tl_(1_x)V_x 关键词：     

高温超导体脉冲磁化过程中的磁热不稳定性

该主要研究了高温超导体在脉冲磁场中的磁热稳定性，与传统低温超导体相比，ＨＴＳ所不同的是最不稳定的状态发生在磁通跳跃区，理论上借助Ｅ－ｊ曲线和有限热扩散方程推导了磁通跳跃场与变场速率的关系表达式：Ｂｊ＝Ｆ其规律基本与实验结果相符合，同时从实验中发现磁热不稳定性对永磁体脉冲磁化效果有巨大的影响。     

高温超导电性的电子配对机制

高温超导电性的电子配对机制阎新中（中国科学院物理研究所，北京１０００８０）１０年前，人们首次发现了高温超导材料［１］．从此之后，对高温超导电性的研究成了凝聚态物理的热点领域．通过大量的实验和理论探索，人们在合成新的高温超导材料以及对高温超导机制的认...     

熔融织构YBa2Cu3O7-y各向异性临界电流密度的磁测量

用测磁滞迴线的方法测量熔融织构YBa₂Cu₃O_7-y超导样品的临界电流密度,计算临界电流密度时考虑了退磁场的影响并采用适合于各向异性有限样品的模型,改进了Gyorgy等人最近提出的方法,在不同取向的磁场中测同一样品的磁化曲线,得到三种不同的临界电流密度。 关键词：     

区域熔炼法制备YBa_2Cu_3O_(6+x)的非对数磁弛豫

考虑到有效钉扎势U(J)与临界电流密度的非线性关系,将U(J)展开为三级泰勒级数,最后推导出一个普遍适用于描述高温超导体磁弛豫的等温衰减方程,并用这一方程研究了具有高J_c,强钉扎的区域熔炼法制备YBa_2Cu_3O_(6+x)的磁弛豫,而且对目前被普遍采用的几个钉扎模型进行了讨论. 关键词：     

大有效面积的高Tc rf SQUID

关键词： c rf SQUID')" href="#">高T_c rf SQUID 新型结构 大有效面积 磁通聚焦器     

INFLUENCE OF SPIN AND CHARGE FLUCTUATIONS ON THE HIGH-Tc SUPERCONDUCTIVITY

In the framework of the weak coupling theory of superconductivity, we have proved that spin and charge fluctuations in the high-T_c superconductors can pro-duce respectively, pair-breaking and pair-forming effects on the superconductivity resulting from the "generalized BCS mechanism". With the coupling constant for spin fluctuations larger than that for charge fluctuations, they combine to produce a temperature-dependent effective pair-breaking effect, which makes T_c decrease more rapidly than Δ(0), the superconducting gap at T=0, and therefore, enhances the ratio 2Δ(0)/T_c. This provides a reasonable physical interpretation for the relevant experimental results.     

BCS-van Hove方案与高温超导电性

基于BCS—van Hove机制,研究了非磁杂质对高温超导电性的抑制效应,考虑到双层耦合效应和三维耦合效应,将van Hove方案推广到多带BCS模型,计算了超导转变温度与化学势的关系,并与实验结果进行了比较。     

晶格振动、载流子与高温超导电性的关系

系统地从红外光谱的结果论述了晶格振动、载流子与高温超导电性的关系。指出,在高温超导体中,载流子对晶格振动的作用不是屏蔽作用,而是两者之间的局域强耦合相互作用,这种局域的耦合不同于普通的电声子耦合。在此基础上,通过理论和实验研究,论述了局域耦合强度及其整体效应与超导电性的关系。 关键词：     

准二维玻色凝聚、氧空位、高温超导

本文从准二维玻色凝聚出发,研究了层状高温超导氧化物材料中,层厚度和氧空位对临界温度的影响。所得结论应用到YBa₂Cu₃O₇中,与已知的实验定性符合。 关键词：     

INFLUENCE OF SPIN AND CHARGE FLUCTUATIONS ON THE HIGH-Tc SUPERCONDUCTIVITY

In the framework of the weak coupling theory of superconductivity, we have proved that spin and charge fluctuations in the high-T_c superconductors can pro-duce respectively, pair-breaking and pair-forming effects on the superconductivity resulting from the "generalized BCS mechanism". With the coupling constant for spin fluctuations larger than that for charge fluctuations, they combine to produce a temperature-dependent effective pair-breaking effect, which makes T_c decrease more rapidly than Δ(0), the superconducting gap at T=0, and therefore, enhances the ratio 2Δ(0)/T_c. This provides a reasonable physical interpretation for the relevant experimental results.     

非稀土元素对硫氧化镧铽发光性能的影响

本文研究了22种非稀土元素对La2O2S:Tb阴极射线激发发光性能的影响,其中周期表第Ⅱ族元素对发光亮度起增强作用,而Fe、Co、Ni、Cr等重金属对发光亮度起猝灭作用,必须从原科中除去.除Fe外,非稀土杂质的量如<0.1%,一般对La2O2S:Tb的色度和余辉无明显的影响.     

贫铀药型罩材料中微量杂质对聚能射流性能的影响

 通过对贫铀药型罩的静破甲实验，研究了材料中微量元素对射流性能的影响。实验结果表明，贫铀中的碳含量对射流性能起着非常重要的作用，随着碳含量的增加，静破甲威力下降十分显著。最后讨论了有害微量杂质对射流造成影响的原因，指出有害杂质可以以点缺陷形式或向晶界偏聚的形式存在于材料中，它们对材料的滑移变形均起到阻碍作用，其结果造成材料延展性能下降。     

INVESTIGATION OF THE EFFECT OF SLOW NEUTRON IRRADIATION ON HALOGEN-DOPED HIGH-Tc SUPERCONDUCTORS AND ITS MECHANISM

Irradiation effect of low-fluence (-10⁸ n/cm² ) slow neutrons on halogen-doped superconductors is presented in this paper. And the mechanism of the effect is also described from the viewpoint of nuclear physics for both fast and slow neutrons on high-temperature superconductors (HTSC). It is shown ex-perimentally and theoretically that slow neutrons of low fluence has a similar irradiation effect to that of fast neutron beams with an energy E_n>0.1 MeV and fluence 10¹⁶-10¹⁸ n/cm²-However,quite differ-ent mechanisms are involved in them: Fast neutrons transfer their energies through elastic scattering in HTSC, whereas slow neutrons give off their energies during the slow neutron capture (n,γ) reaction.     

INFLUENCE OF OXYGEN UPON THE SUPERCONDUCTIVITY OF THE Pb-DOPED 2223 SUPERCONDUCTOR

The influences of oxygen content (by quenching from different temperatures in air or oxygen) and its re-distribution (by annealing in nitrogen at 200℃) on T_c and room temperature resistivity were studied. It was found that T_c as a function of oxygen content or charge carrier concentration exhibits a maximum. Upon oxygen re-distribution, the room temperature resistivity would always inclose but T_c would change in a complicated way. T_c increases for the oxygen-rich state and decreases for the oxygen-deficient state Internal friction measurements showed that there are two kinds of oxygen defects in the Bi₂-O₂ layers. One is the isolated oxygen interstitials and the other is oxygen vacancies on the excess oxygen chains. It is proposed that the isolated interstitial oxygen will produce a set of impurity states near the Fermi level, and will create holes on the Cu3d-O2p band through charge transfer from the Cu3d-O2p band to the impurity states. The content of the isolated oxygen interstitial is believed to be the major factor for determining the charge carrier concentration. Variation of T_c and room temperature resistivity with oxygen re-distribution is sat-isfactorily explained as to be induced by combination of oxygen interstitials with oxygen vacancies on the excess oxygen-chains.