Tl_4Ba_3Ca_3Cu_4O_y系统的超导电性和磁化反常  

THE SUPERCONDUCTIVITY AND ANOMALOUS MAGNETIZATION OF THE Tl_4Ba_3Ca_3Cu_4O_y SYSTEM

作　　者：曹效文[1] 黄孙利 张凤英[1] 龙香云 彭获田 彭秋云[2] 齐志伟[2] 吴裕生[2] 方俊人 张伟杰[3] 刘宏宝[3] 毛向雷 张裕恒 

机构地区：[1]中国科学院等离子体物理所 [2]长沙矿冶研究院 [3]中国科学技术大学物理系

出　　处：《低温物理学报》1990年第3期206-212,共7页Low Temperature Physical Letters

摘　　要：Tl_4Ba_3Ca_3Cu_4O_y 氧化物超导体中存在100K 和120K 两个超导相.测量电流为10mA 时,零电阻超导 T_c 为119K.DC 磁化结果表明:在77K 时不可逆场约为2200O_e,冻结磁通密度11.6G,样品是弱钉扎Ⅱ类超导体.Meissner 效应测量结果表明:Meissner 信号的61%是120K 相的贡献,39%是100K 相的贡献.超导体积的上限和下限的比较,不同磁场和测量电流的 R(T)超导转变以及磁化反常表明:我们的样品中存在着大量的弱连接超导电性,并构成邻近效应超导体,研究了它的日 H_(c2)(T).并由邻近效应超导体的磁化曲线演算出它的超导参量.Two superconducting phases,i.e.the 100K phase and the 120K one,exist in the Cu4Oy oxide superconductor.The zero resistance Tc is 119K at 10mA measuring current.The DC magnetization results show that at 77K the magnetization is nearly reversible in the applied field of above 2200 Oe and the forgen flux density is 11.6G.So our sample is still of a weak pinning type II superconductor.The expesimental result of Meissner effect shows that 61% of Meissner signal results from the 120K phase and the rest from the 100K phase.It has been found that there exist a great deal of weak-link superconductivity and it results in a proximity effect superconductor in our sample.This can be seen by the comparison between the upper and lower limits of the superconducting volume fraction,the measurments of resistance transition at both varions applied fields and measuring currents,and the analysis of ansmalous magnetixation.The magnetization charateristics and some parameters of the proximity effect superconductor have ben obtained,and the Hc2(T) of this superconductor has been studied.

关 键 词：氧化物 超导体 超导电性 磁化 反常 

分 类 号：TM262[一般工业技术—材料科学与工程]