THE MEISSNER EFFECT IN TaSe_3

TaSe_3 中的迈斯纳效应

基本信息

批准号：
62540222
负责人：
NAGATA Shoichi
金额：
$ 1.41万
依托单位：
Muroran Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

THE MEISSNER EFFECT IN TaSe_3 The Meissner effect of the quasi-one-dimensional conductor TaSe_3 is studied using a SQUID magnetometer. Susceptibility x does not show any significant variation of diamagnetism, with magnetic fields parallel and perpendicular to crystalline b-axis over a low magnetic field range of 7.2 mOe to 4.0 Oe. The diamagnetism is quite weak and the value of chi is much less than -3.OX10^<-3> emu/cm^3. Furthermore, thd susceptibility chi does not exhibit any indication of an abrupt change at 2.1 K. A single whisker consists of many fibers where some fibers (very thin filament-like) become superconducting below 2.1 K.Resistivity of TaSe_3 drops near zero below 2.1 K. Why is the Meissner effect suppressed quite strongly in TaSe_3 ? A basic origin of this small diamagnetism is discussed on the basis of numerical computer calculations for the London model.As a simplified model, the diamagnetic susceptibility chi for a infinite cylinder having radius, a , is calculated systematically as a function of a/lambda, here lambda is the London penetration depth. In TaSe_3, the superconducting region is strictly restricted to extremely thin filaments along the b-axis in the single whisker. Furthermore. these superconducting filaments are individually isolated above 0.40 K in the whisker. The radii of the filaments are much less than lambda ( at most a/lambda <less than or equal>0.30 ), then, the magnetic flux will penetrate uniformly.Consequently the Meissner effect is substantially smeared out.It should be noted that our experimental results give the single whisker's intrinsic material property. Our results could totally differ from that of the large amount of massive specimens which are randomly oriented and are greatly interpenetrating.

TaSe_3 中的迈斯纳效应使用 SQUID 磁力计研究了准一维导体 TaSe_3 的迈斯纳效应。磁化率 x 没有显示任何显着的抗磁性变化，在 7.2 mOe 至 4.0 Oe 的低磁场范围内，磁场平行和垂直于晶体 b 轴。抗磁性很弱，chi值远小于-3.OX10^<-3> emu/cm^3。此外，thd 磁化率 chi 在 2.1 K 时没有表现出任何突然变化的迹象。单个晶须由许多纤维组成，其中一些纤维（非常细的丝状）在 2.1 K 以下变得超导。TaSe_3 的电阻率在 2.1 K 以下下降到接近于零为什么迈斯纳效应在 TaSe_3 中受到强烈抑制？在伦敦模型的数值计算机计算的基础上讨论了这种小抗磁性的基本起源。作为一个简化模型，半径为 a 的无限圆柱体的抗磁性磁化率 chi 被系统地计算为 a/lambda 的函数，这里 lambda 是伦敦渗透深度。在 TaSe_3 中，超导区域严格限制在单晶须中沿 b 轴的极细细丝。此外。这些超导细丝在晶须中的温度高于 0.40 K 时被单独隔离。细丝的半径远小于 lambda（至多 a/lambda <小于或等于>0.30），那么磁通量会均匀地穿透。因此迈斯纳效应基本上被抹掉了。需要注意的是，我们的实验结果给出了单晶须的固有材料特性。我们的结果可能与大量随机定向且相互渗透的大量样本的结果完全不同。