Search for Magnetic-Field-Induced-Superconductivity in Heavy Fermion Systems.

寻找重费米子系统中的磁场感应超导性。

基本信息

批准号：
61460034
负责人：
KOBAYASHI Norio
金额：
$ 4.35万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1988
项目状态：
已结题

项目摘要

In heavy Fermion systems and magnetic superconducting systems, the possibility of the reentrant superconductivity in the high magnetic field region has been predicted by Tachiki et al. This reentrant behavior is called as "magnetic-field-induced-superconductivity"(MFIS). Following their prediction, Isino et al descovered the MFIS in a Chevrel Phase compound, Eu_<1-x>Sn_xMo_6S_7. However, in heavy Fermion systems, the MFIS has not been discovered. We performed this project in order to clarify the origin of the MFIS in Eu_<1-x>Sn_xMo_6S_7 and to search for the possibility of the MFIS in the heavy Fermion systems with rare earth elements (RE) or Uranium element.1. The electrical resistance under magnetic fields up to 23 T and the speciffic heat under fields up to 6 T of the compounds Eu_<0.8>Sn_<0.2>Mo_6S_<7-y>Se_y(0 y 0.7) have been measured. The specific heat shows Schottky contribution due to En^<2+> ions in ^8S_<7/2>, which have magnetic moments. Furthermore we have observed the hyste … More resis of the electrical resistance in the field range where superconductive-normal-superconductive transition appear. This result on the hysteresis prove that the direction of the net magnetic field acting on the conduction electron spins is opposite to that of the applied field. From this fact, it is confirmed directly that the mechanism of the MFIS in this system oiriginates from the jaccarino-peter effect. 2. Several Th_2Cr_2Si_2 type compounds containing rare earth elements (Ce, La, Yb) and UTX type (T=Pd, Pt, Ni and X=Ge, Si, In) compounds were prepared by an arc-melting. The properties of these compounds were investigated by the electrical resistance, magnetization and specific heat measurements. Among these compounds, the superconductivity was observed in LaPd_2Ge_2, YbPd_2Ge_2 and UNiSi. While LaPd_2Ge_2 and YbPd_2Ge_2 show the usual BCS like superconductivity, UNiSi behaves weak heavy fermion properties. however, the MFIS was not found in our samples. Investigations of superconducting compounds containing u are continued. Less

在重费米子系统和磁超导系统中，Tachiki等人预测了在高磁场区域出现重入超导的可能性，这种重入行为被称为“磁场诱导超导”（MFIS）。 Isino等人在Chevrel相化合物Eu_<1-x>Sn_xMo_6S_7中发现了MFIS，但是在重费米子中。系统中，MFIS尚未被发现。我们进行这个项目是为了澄清Eu_<1-x>Sn_xMo_6S_7中MFIS的起源，并寻找稀土元素重费米子系统（RE）中MFIS的可能性。 ) 或铀元素。1. 化合物在磁场下的电阻高达 23 T，在磁场下的比热高达 6 T。测量了 Eu_<0.8>Sn_<0.2>Mo_6S_<7-y>Se_y(0 y 0.7) 的比热，显示了 ^8S_<7/2> 中 En^<2+> 离子的肖特基贡献。进一步的磁矩。我们观察到出现超导-正常-超导转变的磁场范围内的磁滞电阻。这一结果证明了磁滞现象。作用于传导电子自旋的净磁场方向与施加场方向相反，由此直接证实了该系统中的MFIS机制源于jaccarino-peter效应2。制备了几种含稀土元素(Ce、La、Yb)的Th_2Cr_2Si_2型化合物和UTX型(T=Pd、Pt、Ni和X=Ge、Si、In)化合物。通过电阻、磁化强度和比热测量研究了这些化合物的超导性，其中LaPd_2Ge_2、YbPd_2Ge_2和UNiSi表现出类似BCS的超导性。然而，MFIS 的重费米子性质较弱。含u超导化合物的研究仍在继续。